summary refs log tree commit diff stats
path: root/lib/std
diff options
context:
space:
mode:
Diffstat (limited to 'lib/std')
-rw-r--r--lib/std/appdirs.nim94
-rw-r--r--lib/std/assertions.nim23
-rw-r--r--lib/std/cmdline.nim313
-rw-r--r--lib/std/decls.nim13
-rw-r--r--lib/std/dirs.nim135
-rw-r--r--lib/std/editdistance.nim4
-rw-r--r--lib/std/effecttraits.nim2
-rw-r--r--lib/std/enumerate.nim4
-rw-r--r--lib/std/enumutils.nim40
-rw-r--r--lib/std/envvars.nim49
-rw-r--r--lib/std/exitprocs.nim36
-rw-r--r--lib/std/files.nim46
-rw-r--r--lib/std/formatfloat.nim55
-rw-r--r--lib/std/genasts.nim6
-rw-r--r--lib/std/isolation.nim6
-rw-r--r--lib/std/jsbigints.nim14
-rw-r--r--lib/std/jsfetch.nim11
-rw-r--r--lib/std/jsformdata.nim16
-rw-r--r--lib/std/jsonutils.nim119
-rw-r--r--lib/std/monotimes.nim4
-rw-r--r--lib/std/objectdollar.nim2
-rw-r--r--lib/std/oserrors.nim19
-rw-r--r--lib/std/outparams.nim38
-rw-r--r--lib/std/packedsets.nim33
-rw-r--r--lib/std/paths.nim302
-rw-r--r--lib/std/private/dbutils.nim15
-rw-r--r--lib/std/private/digitsutils.nim15
-rw-r--r--lib/std/private/dragonbox.nim52
-rw-r--r--lib/std/private/gitutils.nim16
-rw-r--r--lib/std/private/globs.nim10
-rw-r--r--lib/std/private/jsutils.nim23
-rw-r--r--lib/std/private/miscdollars.nim16
-rw-r--r--lib/std/private/osappdirs.nim176
-rw-r--r--lib/std/private/oscommon.nim186
-rw-r--r--lib/std/private/osdirs.nim570
-rw-r--r--lib/std/private/osfiles.nim416
-rw-r--r--lib/std/private/ospaths2.nim1030
-rw-r--r--lib/std/private/osseps.nim113
-rw-r--r--lib/std/private/ossymlinks.nim78
-rw-r--r--lib/std/private/schubfach.nim26
-rw-r--r--lib/std/private/since.nim10
-rw-r--r--lib/std/private/strimpl.nim37
-rw-r--r--lib/std/private/syslocks.nim234
-rw-r--r--lib/std/private/threadtypes.nim176
-rw-r--r--lib/std/private/underscored_calls.nim22
-rw-r--r--lib/std/private/win_setenv.nim33
-rw-r--r--lib/std/setutils.nim2
-rw-r--r--lib/std/sha1.nim9
-rw-r--r--lib/std/socketstreams.nim63
-rw-r--r--lib/std/staticos.nim13
-rw-r--r--lib/std/strbasics.nim4
-rw-r--r--lib/std/sums.nim80
-rw-r--r--lib/std/symlinks.nim33
-rw-r--r--lib/std/syncio.nim150
-rw-r--r--lib/std/sysatomics.nim376
-rw-r--r--lib/std/sysrand.nim36
-rw-r--r--lib/std/tasks.nim110
-rw-r--r--lib/std/tempfiles.nim8
-rw-r--r--lib/std/time_t.nim4
-rw-r--r--lib/std/typedthreads.nim305
-rw-r--r--lib/std/varints.nim12
-rw-r--r--lib/std/widestrs.nim239
-rw-r--r--lib/std/with.nim11
-rw-r--r--lib/std/wordwrap.nim2
-rw-r--r--lib/std/wrapnils.nim24
65 files changed, 5487 insertions, 632 deletions
diff --git a/lib/std/appdirs.nim b/lib/std/appdirs.nim
new file mode 100644
index 000000000..963451efe
--- /dev/null
+++ b/lib/std/appdirs.nim
@@ -0,0 +1,94 @@
+## This module implements helpers for determining special directories used by apps.
+
+## .. importdoc:: paths.nim
+
+from std/private/osappdirs import nil
+import std/paths
+import std/envvars
+
+proc getHomeDir*(): Path {.inline, tags: [ReadEnvEffect, ReadIOEffect].} =
+  ## Returns the home directory of the current user.
+  ##
+  ## This proc is wrapped by the `expandTilde proc`_
+  ## for the convenience of processing paths coming from user configuration files.
+  ##
+  ## See also:
+  ## * `getConfigDir proc`_
+  ## * `getTempDir proc`_
+  result = Path(osappdirs.getHomeDir())
+
+proc getDataDir*(): Path {.inline, tags: [ReadEnvEffect, ReadIOEffect].} =
+  ## Returns the data directory of the current user for applications.
+  ## 
+  ## On non-Windows OSs, this proc conforms to the XDG Base Directory
+  ## spec. Thus, this proc returns the value of the `XDG_DATA_HOME` environment
+  ## variable if it is set, otherwise it returns the default configuration
+  ## directory ("~/.local/share" or "~/Library/Application Support" on macOS).
+  ## 
+  ## See also:
+  ## * `getHomeDir proc`_
+  ## * `getConfigDir proc`_
+  ## * `getTempDir proc`_
+  ## * `expandTilde proc`_
+  ## * `getCurrentDir proc`_
+  ## * `setCurrentDir proc`_
+  result = Path(osappdirs.getDataDir())
+
+proc getConfigDir*(): Path {.inline, tags: [ReadEnvEffect, ReadIOEffect].} =
+  ## Returns the config directory of the current user for applications.
+  ##
+  ## On non-Windows OSs, this proc conforms to the XDG Base Directory
+  ## spec. Thus, this proc returns the value of the `XDG_CONFIG_HOME` environment
+  ## variable if it is set, otherwise it returns the default configuration
+  ## directory ("~/.config/").
+  ##
+  ## An OS-dependent trailing slash is always present at the end of the
+  ## returned string: `\\` on Windows and `/` on all other OSs.
+  ##
+  ## See also:
+  ## * `getHomeDir proc`_
+  ## * `getTempDir proc`_
+  result = Path(osappdirs.getConfigDir())
+
+proc getCacheDir*(): Path {.inline.} =
+  ## Returns the cache directory of the current user for applications.
+  ##
+  ## This makes use of the following environment variables:
+  ##
+  ## * On Windows: `getEnv("LOCALAPPDATA")`
+  ##
+  ## * On macOS: `getEnv("XDG_CACHE_HOME", getEnv("HOME") / "Library/Caches")`
+  ##
+  ## * On other platforms: `getEnv("XDG_CACHE_HOME", getEnv("HOME") / ".cache")`
+  ##
+  ## **See also:**
+  ## * `getHomeDir proc`_
+  ## * `getTempDir proc`_
+  ## * `getConfigDir proc`_
+  # follows https://crates.io/crates/platform-dirs
+  result = Path(osappdirs.getCacheDir())
+
+proc getCacheDir*(app: Path): Path {.inline.} =
+  ## Returns the cache directory for an application `app`.
+  ##
+  ## * On Windows, this uses: `getCacheDir() / app / "cache"`
+  ## * On other platforms, this uses: `getCacheDir() / app`
+  result = Path(osappdirs.getCacheDir(app.string))
+
+proc getTempDir*(): Path {.inline, tags: [ReadEnvEffect, ReadIOEffect].} =
+  ## Returns the temporary directory of the current user for applications to
+  ## save temporary files in.
+  ##
+  ## On Windows, it calls [GetTempPath](https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-gettemppathw).
+  ## On Posix based platforms, it will check `TMPDIR`, `TEMP`, `TMP` and `TEMPDIR` environment variables in order.
+  ## On all platforms, `/tmp` will be returned if the procs fails.
+  ##
+  ## You can override this implementation
+  ## by adding `-d:tempDir=mytempname` to your compiler invocation.
+  ##
+  ## .. Note:: This proc does not check whether the returned path exists.
+  ##
+  ## See also:
+  ## * `getHomeDir proc`_
+  ## * `getConfigDir proc`_
+  result = Path(osappdirs.getTempDir())
diff --git a/lib/std/assertions.nim b/lib/std/assertions.nim
index 0bc4653f2..56c37d205 100644
--- a/lib/std/assertions.nim
+++ b/lib/std/assertions.nim
@@ -7,11 +7,12 @@
 #    distribution, for details about the copyright.
 #
 
-## This module implements assertion handling.
-
-when not declared(sysFatal):
+when not defined(nimPreviewSlimSystem) and not declared(sysFatal):
+  include "system/rawquits"
   include "system/fatal"
 
+## This module implements assertion handling.
+
 import std/private/miscdollars
 # ---------------------------------------------------------------------------
 # helpers
@@ -26,22 +27,18 @@ proc `$`(info: InstantiationInfo): string =
 
 # ---------------------------------------------------------------------------
 
-when not defined(nimHasSinkInference):
-  {.pragma: nosinks.}
 
 proc raiseAssert*(msg: string) {.noinline, noreturn, nosinks.} =
   ## Raises an `AssertionDefect` with `msg`.
-  sysFatal(AssertionDefect, msg)
+  when defined(nimPreviewSlimSystem):
+    raise newException(AssertionDefect, msg)
+  else:
+    sysFatal(AssertionDefect, msg)
 
 proc failedAssertImpl*(msg: string) {.raises: [], tags: [].} =
   ## Raises an `AssertionDefect` with `msg`, but this is hidden
   ## from the effect system. Called when an assertion failed.
-  # trick the compiler to not list `AssertionDefect` when called
-  # by `assert`.
-  # xxx simplify this pending bootstrap >= 1.4.0, after which cast not needed
-  # anymore since `Defect` can't be raised.
-  type Hide = proc (msg: string) {.noinline, raises: [], noSideEffect, tags: [].}
-  cast[Hide](raiseAssert)(msg)
+  raiseAssert(msg)
 
 template assertImpl(cond: bool, msg: string, expr: string, enabled: static[bool]) =
   when enabled:
@@ -101,6 +98,7 @@ template doAssertRaises*(exception: typedesc, code: untyped) =
   const begin = "expected raising '" & astToStr(exception) & "', instead"
   const msgEnd = " by: " & astToStr(code)
   template raisedForeign {.gensym.} = raiseAssert(begin & " raised foreign exception" & msgEnd)
+  {.push warning[BareExcept]:off.}
   when Exception is exception:
     try:
       if true:
@@ -119,5 +117,6 @@ template doAssertRaises*(exception: typedesc, code: untyped) =
       mixin `$` # alternatively, we could define $cstring in this module
       raiseAssert(begin & " raised '" & $e.name & "'" & msgEnd)
     except: raisedForeign()
+  {.pop.}
   if wrong:
     raiseAssert(begin & " nothing was raised" & msgEnd)
diff --git a/lib/std/cmdline.nim b/lib/std/cmdline.nim
new file mode 100644
index 000000000..0ba4619e5
--- /dev/null
+++ b/lib/std/cmdline.nim
@@ -0,0 +1,313 @@
+#

+#

+#            Nim's Runtime Library

+#        (c) Copyright 2022 Andreas Rumpf

+#

+#    See the file "copying.txt", included in this

+#    distribution, for details about the copyright.

+#

+

+## This module contains system facilities for reading command

+## line parameters.

+

+## **See also:**

+## * `parseopt module <parseopt.html>`_ for command-line parser beyond

+##   `parseCmdLine proc`_

+

+

+include system/inclrtl

+

+when defined(nimPreviewSlimSystem):

+  import std/widestrs

+  

+when defined(nodejs):

+  from std/private/oscommon import ReadDirEffect

+

+

+const weirdTarget = defined(nimscript) or defined(js)

+

+

+when weirdTarget:

+  discard

+elif defined(windows):

+  import std/winlean

+elif defined(posix):

+  import std/posix

+else:

+  {.error: "The cmdline module has not been implemented for the target platform.".}

+

+

+# Needed by windows in order to obtain the command line for targets

+# other than command line targets

+when defined(windows) and not weirdTarget:

+  template getCommandLine*(): untyped = getCommandLineW()

+

+

+proc parseCmdLine*(c: string): seq[string] {.

+  noSideEffect, rtl, extern: "nos$1".} =

+  ## Splits a `command line`:idx: into several components.

+  ##

+  ## **Note**: This proc is only occasionally useful, better use the

+  ## `parseopt module <parseopt.html>`_.

+  ##

+  ## On Windows, it uses the `following parsing rules

+  ## <http://msdn.microsoft.com/en-us/library/17w5ykft.aspx>`_:

+  ##

+  ## * Arguments are delimited by white space, which is either a space or a tab.

+  ## * The caret character (^) is not recognized as an escape character or

+  ##   delimiter. The character is handled completely by the command-line parser

+  ##   in the operating system before being passed to the argv array in the

+  ##   program.

+  ## * A string surrounded by double quotation marks ("string") is interpreted

+  ##   as a single argument, regardless of white space contained within. A

+  ##   quoted string can be embedded in an argument.

+  ## * A double quotation mark preceded by a backslash (\") is interpreted as a

+  ##   literal double quotation mark character (").

+  ## * Backslashes are interpreted literally, unless they immediately precede

+  ##   a double quotation mark.

+  ## * If an even number of backslashes is followed by a double quotation mark,

+  ##   one backslash is placed in the argv array for every pair of backslashes,

+  ##   and the double quotation mark is interpreted as a string delimiter.

+  ## * If an odd number of backslashes is followed by a double quotation mark,

+  ##   one backslash is placed in the argv array for every pair of backslashes,

+  ##   and the double quotation mark is "escaped" by the remaining backslash,

+  ##   causing a literal double quotation mark (") to be placed in argv.

+  ##

+  ## On Posix systems, it uses the following parsing rules:

+  ## Components are separated by whitespace unless the whitespace

+  ## occurs within ``"`` or ``'`` quotes.

+  ##

+  ## See also:

+  ## * `parseopt module <parseopt.html>`_

+  ## * `paramCount proc`_

+  ## * `paramStr proc`_

+  ## * `commandLineParams proc`_

+

+  result = @[]

+  var i = 0

+  var a = ""

+  while true:

+    setLen(a, 0)

+    # eat all delimiting whitespace

+    while i < c.len and c[i] in {' ', '\t', '\l', '\r'}: inc(i)

+    if i >= c.len: break

+    when defined(windows):

+      # parse a single argument according to the above rules:

+      var inQuote = false

+      while i < c.len:

+        case c[i]

+        of '\\':

+          var j = i

+          while j < c.len and c[j] == '\\': inc(j)

+          if j < c.len and c[j] == '"':

+            for k in 1..(j-i) div 2: a.add('\\')

+            if (j-i) mod 2 == 0:

+              i = j

+            else:

+              a.add('"')

+              i = j+1

+          else:

+            a.add(c[i])

+            inc(i)

+        of '"':

+          inc(i)

+          if not inQuote: inQuote = true

+          elif i < c.len and c[i] == '"':

+            a.add(c[i])

+            inc(i)

+          else:

+            inQuote = false

+            break

+        of ' ', '\t':

+          if not inQuote: break

+          a.add(c[i])

+          inc(i)

+        else:

+          a.add(c[i])

+          inc(i)

+    else:

+      case c[i]

+      of '\'', '\"':

+        var delim = c[i]

+        inc(i) # skip ' or "

+        while i < c.len and c[i] != delim:

+          add a, c[i]

+          inc(i)

+        if i < c.len: inc(i)

+      else:

+        while i < c.len and c[i] > ' ':

+          add(a, c[i])

+          inc(i)

+    add(result, move a)

+

+when defined(nimdoc):

+  # Common forward declaration docstring block for parameter retrieval procs.

+  proc paramCount*(): int {.tags: [ReadIOEffect].} =

+    ## Returns the number of `command line arguments`:idx: given to the

+    ## application.

+    ##

+    ## Unlike `argc`:idx: in C, if your binary was called without parameters this

+    ## will return zero.

+    ## You can query each individual parameter with `paramStr proc`_

+    ## or retrieve all of them in one go with `commandLineParams proc`_.

+    ##

+    ## **Availability**: When generating a dynamic library (see `--app:lib`) on

+    ## Posix this proc is not defined.

+    ## Test for availability using `declared() <system.html#declared,untyped>`_.

+    ##

+    ## See also:

+    ## * `parseopt module <parseopt.html>`_

+    ## * `parseCmdLine proc`_

+    ## * `paramStr proc`_

+    ## * `commandLineParams proc`_

+    ##

+    ## **Examples:**

+    ##

+    ##   ```nim

+    ##   when declared(paramCount):

+    ##     # Use paramCount() here

+    ##   else:

+    ##     # Do something else!

+    ##   ```

+

+  proc paramStr*(i: int): string {.tags: [ReadIOEffect].} =

+    ## Returns the `i`-th `command line argument`:idx: given to the application.

+    ##

+    ## `i` should be in the range `1..paramCount()`, the `IndexDefect`

+    ## exception will be raised for invalid values. Instead of iterating

+    ## over `paramCount()`_ with this proc you can

+    ## call the convenience `commandLineParams()`_.

+    ##

+    ## Similarly to `argv`:idx: in C,

+    ## it is possible to call `paramStr(0)` but this will return OS specific

+    ## contents (usually the name of the invoked executable). You should avoid

+    ## this and call `getAppFilename() <os.html#getAppFilename>`_ instead.

+    ##

+    ## **Availability**: When generating a dynamic library (see `--app:lib`) on

+    ## Posix this proc is not defined.

+    ## Test for availability using `declared() <system.html#declared,untyped>`_.

+    ##

+    ## See also:

+    ## * `parseopt module <parseopt.html>`_

+    ## * `parseCmdLine proc`_

+    ## * `paramCount proc`_

+    ## * `commandLineParams proc`_

+    ## * `getAppFilename proc <os.html#getAppFilename>`_

+    ##

+    ## **Examples:**

+    ##

+    ##   ```nim

+    ##   when declared(paramStr):

+    ##     # Use paramStr() here

+    ##   else:

+    ##     # Do something else!

+    ##   ```

+

+elif defined(nimscript): discard

+elif defined(nodejs):

+  type Argv = object of JsRoot

+  let argv {.importjs: "process.argv".} : Argv

+  proc len(argv: Argv): int {.importjs: "#.length".}

+  proc `[]`(argv: Argv, i: int): cstring {.importjs: "#[#]".}

+

+  proc paramCount*(): int {.tags: [ReadDirEffect].} =

+    result = argv.len - 2

+

+  proc paramStr*(i: int): string {.tags: [ReadIOEffect].} =

+    let i = i + 1

+    if i < argv.len and i >= 0:

+      result = $argv[i]

+    else:

+      raise newException(IndexDefect, formatErrorIndexBound(i - 1, argv.len - 2))

+elif defined(windows):

+  # Since we support GUI applications with Nim, we sometimes generate

+  # a WinMain entry proc. But a WinMain proc has no access to the parsed

+  # command line arguments. The way to get them differs. Thus we parse them

+  # ourselves. This has the additional benefit that the program's behaviour

+  # is always the same -- independent of the used C compiler.

+  var

+    ownArgv {.threadvar.}: seq[string]

+    ownParsedArgv {.threadvar.}: bool

+

+  proc paramCount*(): int {.rtl, extern: "nos$1", tags: [ReadIOEffect].} =

+    # Docstring in nimdoc block.

+    if not ownParsedArgv:

+      ownArgv = parseCmdLine($getCommandLine())

+      ownParsedArgv = true

+    result = ownArgv.len-1

+

+  proc paramStr*(i: int): string {.rtl, extern: "nos$1",

+    tags: [ReadIOEffect].} =

+    # Docstring in nimdoc block.

+    if not ownParsedArgv:

+      ownArgv = parseCmdLine($getCommandLine())

+      ownParsedArgv = true

+    if i < ownArgv.len and i >= 0:

+      result = ownArgv[i]

+    else:

+      raise newException(IndexDefect, formatErrorIndexBound(i, ownArgv.len-1))

+

+elif defined(genode):

+  proc paramStr*(i: int): string =

+    raise newException(OSError, "paramStr is not implemented on Genode")

+

+  proc paramCount*(): int =

+    raise newException(OSError, "paramCount is not implemented on Genode")

+elif weirdTarget or (defined(posix) and appType == "lib"):

+  proc paramStr*(i: int): string {.tags: [ReadIOEffect].} =

+    raise newException(OSError, "paramStr is not implemented on current platform")

+

+  proc paramCount*(): int {.tags: [ReadIOEffect].} =

+    raise newException(OSError, "paramCount is not implemented on current platform")

+elif not defined(createNimRtl) and

+  not(defined(posix) and appType == "lib"):

+  # On Posix, there is no portable way to get the command line from a DLL.

+  var

+    cmdCount {.importc: "cmdCount".}: cint

+    cmdLine {.importc: "cmdLine".}: cstringArray

+

+  proc paramStr*(i: int): string {.tags: [ReadIOEffect].} =

+    # Docstring in nimdoc block.

+    if i < cmdCount and i >= 0:

+      result = $cmdLine[i]

+    else:

+      raise newException(IndexDefect, formatErrorIndexBound(i, cmdCount-1))

+

+  proc paramCount*(): int {.tags: [ReadIOEffect].} =

+    # Docstring in nimdoc block.

+    result = cmdCount-1

+

+when declared(paramCount) or defined(nimdoc):

+  proc commandLineParams*(): seq[string] =

+    ## Convenience proc which returns the command line parameters.

+    ##

+    ## This returns **only** the parameters. If you want to get the application

+    ## executable filename, call `getAppFilename() <os.html#getAppFilename>`_.

+    ##

+    ## **Availability**: On Posix there is no portable way to get the command

+    ## line from a DLL and thus the proc isn't defined in this environment. You

+    ## can test for its availability with `declared()

+    ## <system.html#declared,untyped>`_.

+    ##

+    ## See also:

+    ## * `parseopt module <parseopt.html>`_

+    ## * `parseCmdLine proc`_

+    ## * `paramCount proc`_

+    ## * `paramStr proc`_

+    ## * `getAppFilename proc <os.html#getAppFilename>`_

+    ##

+    ## **Examples:**

+    ##

+    ##   ```nim

+    ##   when declared(commandLineParams):

+    ##     # Use commandLineParams() here

+    ##   else:

+    ##     # Do something else!

+    ##   ```

+    result = @[]

+    for i in 1..paramCount():

+      result.add(paramStr(i))

+else:

+  proc commandLineParams*(): seq[string] {.error:

+  "commandLineParams() unsupported by dynamic libraries".} =

+    discard

diff --git a/lib/std/decls.nim b/lib/std/decls.nim
index 7b907f5e1..bb7ec3593 100644
--- a/lib/std/decls.nim
+++ b/lib/std/decls.nim
@@ -1,16 +1,15 @@
-# see `semLowerLetVarCustomPragma` for compiler support that enables these
-# lowerings
+## This module implements syntax sugar for some declarations.
 
-import macros
+import std/macros
 
 macro byaddr*(sect) =
   ## Allows a syntax for l-value references, being an exact analog to
   ## `auto& a = ex;` in C++.
   ## 
-  ## Warning: This makes use of 2 experimental features, namely nullary
-  ## templates instantiated as symbols and variable macro pragmas.
-  ## For this reason, its behavior is not stable. The current implementation
-  ## allows redefinition, but this is not an intended consequence.
+  ## .. warning:: This makes use of 2 experimental features, namely nullary
+  ##   templates instantiated as symbols and variable macro pragmas.
+  ##   For this reason, its behavior is not stable. The current implementation
+  ##   allows redefinition, but this is not an intended consequence.
   runnableExamples:
     var s = @[10, 11, 12]
     var a {.byaddr.} = s[0]
diff --git a/lib/std/dirs.nim b/lib/std/dirs.nim
new file mode 100644
index 000000000..380d6d08f
--- /dev/null
+++ b/lib/std/dirs.nim
@@ -0,0 +1,135 @@
+## This module implements directory handling.
+
+from std/paths import Path, ReadDirEffect, WriteDirEffect
+
+from std/private/osdirs import dirExists, createDir, existsOrCreateDir, removeDir,
+                               moveDir, walkDir, setCurrentDir,
+                               walkDirRec, PathComponent
+
+export PathComponent
+
+proc dirExists*(dir: Path): bool {.inline, tags: [ReadDirEffect], sideEffect.} =
+  ## Returns true if the directory `dir` exists. If `dir` is a file, false
+  ## is returned. Follows symlinks.
+  result = dirExists(dir.string)
+
+proc createDir*(dir: Path) {.inline, tags: [WriteDirEffect, ReadDirEffect].} =
+  ## Creates the `directory`:idx: `dir`.
+  ##
+  ## The directory may contain several subdirectories that do not exist yet.
+  ## The full path is created. If this fails, `OSError` is raised.
+  ##
+  ## It does **not** fail if the directory already exists because for
+  ## most usages this does not indicate an error.
+  ##
+  ## See also:
+  ## * `removeDir proc`_
+  ## * `existsOrCreateDir proc`_
+  ## * `moveDir proc`_
+  createDir(dir.string)
+
+proc existsOrCreateDir*(dir: Path): bool {.inline, tags: [WriteDirEffect, ReadDirEffect].} =
+  ## Checks if a `directory`:idx: `dir` exists, and creates it otherwise.
+  ##
+  ## Does not create parent directories (raises `OSError` if parent directories do not exist).
+  ## Returns `true` if the directory already exists, and `false` otherwise.
+  ##
+  ## See also:
+  ## * `removeDir proc`_
+  ## * `createDir proc`_
+  ## * `moveDir proc`_
+  result = existsOrCreateDir(dir.string)
+
+proc removeDir*(dir: Path, checkDir = false
+                ) {.inline, tags: [WriteDirEffect, ReadDirEffect].} =
+  ## Removes the directory `dir` including all subdirectories and files
+  ## in `dir` (recursively).
+  ##
+  ## If this fails, `OSError` is raised. This does not fail if the directory never
+  ## existed in the first place, unless `checkDir` = true.
+  ##
+  ## See also:
+  ## * `removeFile proc <files.html#removeFile>`_
+  ## * `existsOrCreateDir proc`_
+  ## * `createDir proc`_
+  ## * `moveDir proc`_
+  removeDir(dir.string, checkDir)
+
+proc moveDir*(source, dest: Path) {.inline, tags: [ReadIOEffect, WriteIOEffect].} =
+  ## Moves a directory from `source` to `dest`.
+  ##
+  ## Symlinks are not followed: if `source` contains symlinks, they themself are
+  ## moved, not their target.
+  ##
+  ## If this fails, `OSError` is raised.
+  ##
+  ## See also:
+  ## * `moveFile proc <files.html#moveFile>`_
+  ## * `removeDir proc`_
+  ## * `existsOrCreateDir proc`_
+  ## * `createDir proc`_
+  moveDir(source.string, dest.string)
+
+iterator walkDir*(dir: Path; relative = false, checkDir = false,
+                 skipSpecial = false):
+    tuple[kind: PathComponent, path: Path] {.tags: [ReadDirEffect].} =
+  ## Walks over the directory `dir` and yields for each directory or file in
+  ## `dir`. The component type and full path for each item are returned.
+  ##
+  ## Walking is not recursive.
+  ## * If `relative` is true (default: false)
+  ##   the resulting path is shortened to be relative to ``dir``,
+  ##   otherwise the full path is returned.
+  ## * If `checkDir` is true, `OSError` is raised when `dir`
+  ##   doesn't exist.
+  ## * If `skipSpecial` is true, then (besides all directories) only *regular*
+  ##   files (**without** special "file" objects like FIFOs, device files,
+  ##   etc) will be yielded on Unix.
+  for (k, p) in walkDir(dir.string, relative, checkDir, skipSpecial):
+    yield (k, Path(p))
+
+iterator walkDirRec*(dir: Path,
+                     yieldFilter = {pcFile}, followFilter = {pcDir},
+                     relative = false, checkDir = false, skipSpecial = false):
+                    Path {.tags: [ReadDirEffect].} =
+  ## Recursively walks over the directory `dir` and yields for each file
+  ## or directory in `dir`.
+  ##
+  ## Options `relative`, `checkdir`, `skipSpecial` are explained in
+  ## [walkDir iterator] description.
+  ##
+  ## .. warning:: Modifying the directory structure while the iterator
+  ##   is traversing may result in undefined behavior!
+  ##
+  ## Walking is recursive. `followFilter` controls the behaviour of the iterator:
+  ##
+  ## =====================   =============================================
+  ## yieldFilter             meaning
+  ## =====================   =============================================
+  ## ``pcFile``              yield real files (default)
+  ## ``pcLinkToFile``        yield symbolic links to files
+  ## ``pcDir``               yield real directories
+  ## ``pcLinkToDir``         yield symbolic links to directories
+  ## =====================   =============================================
+  ##
+  ## =====================   =============================================
+  ## followFilter            meaning
+  ## =====================   =============================================
+  ## ``pcDir``               follow real directories (default)
+  ## ``pcLinkToDir``         follow symbolic links to directories
+  ## =====================   =============================================
+  ##
+  ##
+  ## See also:
+  ## * `walkDir iterator`_
+  for p in walkDirRec(dir.string, yieldFilter, followFilter, relative,
+                      checkDir, skipSpecial):
+    yield Path(p)
+
+proc setCurrentDir*(newDir: Path) {.inline, tags: [].} =
+  ## Sets the `current working directory`:idx:; `OSError`
+  ## is raised if `newDir` cannot been set.
+  ##
+  ## See also:
+  ## * `getCurrentDir proc <paths.html#getCurrentDir>`_
+  osdirs.setCurrentDir(newDir.string)
diff --git a/lib/std/editdistance.nim b/lib/std/editdistance.nim
index 9f29c5c05..40c0017ae 100644
--- a/lib/std/editdistance.nim
+++ b/lib/std/editdistance.nim
@@ -10,7 +10,7 @@
 ## This module implements an algorithm to compute the
 ## `edit distance`:idx: between two Unicode strings.
 
-import unicode
+import std/unicode
 
 proc editDistance*(a, b: string): int {.noSideEffect.} =
   ## Returns the **unicode-rune** edit distance between `a` and `b`.
@@ -18,7 +18,7 @@ proc editDistance*(a, b: string): int {.noSideEffect.} =
   ## This uses the `Levenshtein`:idx: distance algorithm with only a linear
   ## memory overhead.
   runnableExamples: static: doAssert editdistance("Kitten", "Bitten") == 1
-  if len(a) > len(b):
+  if runeLen(a) > runeLen(b):
     # make `b` the longer string
     return editDistance(b, a)
   # strip common prefix
diff --git a/lib/std/effecttraits.nim b/lib/std/effecttraits.nim
index fb057a669..3d1b4ffd3 100644
--- a/lib/std/effecttraits.nim
+++ b/lib/std/effecttraits.nim
@@ -14,7 +14,7 @@
 ## One can test for the existence of this standard module
 ## via `defined(nimHasEffectTraitsModule)`.
 
-import macros
+import std/macros
 
 proc getRaisesListImpl(n: NimNode): NimNode = discard "see compiler/vmops.nim"
 proc getTagsListImpl(n: NimNode): NimNode = discard "see compiler/vmops.nim"
diff --git a/lib/std/enumerate.nim b/lib/std/enumerate.nim
index a8f0e1ba7..beb65ed30 100644
--- a/lib/std/enumerate.nim
+++ b/lib/std/enumerate.nim
@@ -11,7 +11,7 @@
 ## macro system.
 
 import std/private/since
-import macros
+import std/macros
 
 
 macro enumerate*(x: ForLoopStmt): untyped {.since: (1, 3).} =
@@ -21,7 +21,7 @@ macro enumerate*(x: ForLoopStmt): untyped {.since: (1, 3).} =
   ## The default starting count `0` can be manually overridden if needed.
   runnableExamples:
     let a = [10, 20, 30]
-    var b: seq[(int, int)]
+    var b: seq[(int, int)] = @[]
     for i, x in enumerate(a):
       b.add((i, x))
     assert b == @[(0, 10), (1, 20), (2, 30)]
diff --git a/lib/std/enumutils.nim b/lib/std/enumutils.nim
index 9d4ff1bcf..9c338817d 100644
--- a/lib/std/enumutils.nim
+++ b/lib/std/enumutils.nim
@@ -7,8 +7,8 @@
 #    distribution, for details about the copyright.
 #
 
-import macros
-from typetraits import OrdinalEnum, HoleyEnum
+import std/macros
+from std/typetraits import OrdinalEnum, HoleyEnum
 
 when defined(nimPreviewSlimSystem):
   import std/assertions
@@ -21,32 +21,34 @@ macro genEnumCaseStmt*(typ: typedesc, argSym: typed, default: typed,
   # Generates a case stmt, which assigns the correct enum field given
   # a normalized string comparison to the `argSym` input.
   # string normalization is done using passed normalizer.
-  # NOTE: for an enum with fields Foo, Bar, ... we cannot generate
-  # `of "Foo".nimIdentNormalize: Foo`.
-  # This will fail, if the enum is not defined at top level (e.g. in a block).
-  # Thus we check for the field value of the (possible holed enum) and convert
-  # the integer value to the generic argument `typ`.
   let typ = typ.getTypeInst[1]
-  let impl = typ.getImpl[2]
+  let typSym = typ.getTypeImpl.getTypeInst # skip aliases etc to get type sym
+  let impl = typSym.getImpl[2]
   expectKind impl, nnkEnumTy
   let normalizerNode = quote: `normalizer`
   expectKind normalizerNode, nnkSym
   result = nnkCaseStmt.newTree(newCall(normalizerNode, argSym))
   # stores all processed field strings to give error msg for ambiguous enums
   var foundFields: seq[string] = @[]
+  var fVal = ""
   var fStr = "" # string of current field
   var fNum = BiggestInt(0) # int value of current field
   for f in impl:
     case f.kind
     of nnkEmpty: continue # skip first node of `enumTy`
-    of nnkSym, nnkIdent: fStr = f.strVal
+    of nnkSym, nnkIdent:
+      fVal = f.strVal
+      fStr = fVal
     of nnkAccQuoted:
-      fStr = ""
+      fVal = ""
       for ch in f:
-        fStr.add ch.strVal
+        fVal.add ch.strVal
+      fStr = fVal
     of nnkEnumFieldDef:
+      fVal = f[0].strVal
       case f[1].kind
-      of nnkStrLit: fStr = f[1].strVal
+      of nnkStrLit:
+        fStr = f[1].strVal
       of nnkTupleConstr:
         fStr = f[1][1].strVal
         fNum = f[1][0].intVal
@@ -64,7 +66,7 @@ macro genEnumCaseStmt*(typ: typedesc, argSym: typed, default: typed,
     if fNum >= userMin and fNum <= userMax:
       fStr = normalizer(fStr)
       if fStr notin foundFields:
-        result.add nnkOfBranch.newTree(newLit fStr,  nnkCall.newTree(typ, newLit fNum))
+        result.add nnkOfBranch.newTree(newLit fStr, newDotExpr(typ, ident fVal))
         foundFields.add fStr
       else:
         error("Ambiguous enums cannot be parsed, field " & $fStr &
@@ -80,7 +82,7 @@ macro genEnumCaseStmt*(typ: typedesc, argSym: typed, default: typed,
     result.add nnkElse.newTree(default)
 
 macro enumFullRange(a: typed): untyped =
-  newNimNode(nnkCurly).add(a.getType[1][1..^1])
+  newNimNode(nnkBracket).add(a.getType[1][1..^1])
 
 macro enumNames(a: typed): untyped =
   # this could be exported too; in particular this could be useful for enum with holes.
@@ -112,9 +114,9 @@ const invalidSlot = uint8.high
 
 proc genLookup[T: typedesc[HoleyEnum]](_: T): auto =
   const n = span(T)
-  var ret: array[n, uint8]
   var i = 0
   assert n <= invalidSlot.int
+  var ret {.noinit.}: array[n, uint8]
   for ai in mitems(ret): ai = invalidSlot
   for ai in items(T):
     ret[ai.ord - T.low.ord] = uint8(i)
@@ -172,6 +174,9 @@ template symbolRank*[T: enum](a: T): int =
   when T is Ordinal: ord(a) - T.low.ord.static
   else: symbolRankImpl(a)
 
+proc rangeBase(T: typedesc): typedesc {.magic: "TypeTrait".}
+  # skip one level of range; return the base type of a range type
+
 func symbolName*[T: enum](a: T): string =
   ## Returns the symbol name of an enum.
   ##
@@ -190,5 +195,8 @@ func symbolName*[T: enum](a: T): string =
       c1 = 4
       c2 = 20
     assert c1.symbolName == "c1"
-  const names = enumNames(T)
+  when T is range:
+    const names = enumNames(rangeBase T)
+  else:
+    const names = enumNames(T)
   names[a.symbolRank]
diff --git a/lib/std/envvars.nim b/lib/std/envvars.nim
index d7706c17d..a955077ea 100644
--- a/lib/std/envvars.nim
+++ b/lib/std/envvars.nim
@@ -8,7 +8,7 @@
 #
 
 
-## The `std/envvars` module implements environment variables handling.
+## The `std/envvars` module implements environment variable handling.
 import std/oserrors
 
 type
@@ -60,10 +60,16 @@ when not defined(nimscript):
     when defined(windows):
       proc c_putenv(envstring: cstring): cint {.importc: "_putenv", header: "<stdlib.h>".}
       from std/private/win_setenv import setEnvImpl
-      import winlean
-      proc c_wgetenv(varname: WideCString): WideCString {.importc: "_wgetenv",
+      import std/winlean
+      when defined(nimPreviewSlimSystem):
+        import std/widestrs
+
+      type wchar_t {.importc: "wchar_t", header: "<stdlib.h>".} = int16
+      proc c_wgetenv(varname: ptr wchar_t): ptr wchar_t {.importc: "_wgetenv",
           header: "<stdlib.h>".}
-      proc getEnvImpl(env: cstring): WideCString = c_wgetenv(env.newWideCString)
+      proc getEnvImpl(env: cstring): WideCString =
+        let r: WideCString = env.newWideCString
+        cast[WideCString](c_wgetenv(cast[ptr wchar_t](r)))
     else:
       proc c_getenv(env: cstring): cstring {.
         importc: "getenv", header: "<stdlib.h>".}
@@ -88,8 +94,10 @@ when not defined(nimscript):
         assert getEnv("unknownEnv", "doesn't exist") == "doesn't exist"
 
       let env = getEnvImpl(key)
-      if env == nil: return default
-      result = $env
+      if env == nil:
+        result = default
+      else:
+        result = $env
 
     proc existsEnv*(key: string): bool {.tags: [ReadEnvEffect].} =
       ## Checks whether the environment variable named `key` exists.
@@ -103,7 +111,7 @@ when not defined(nimscript):
       runnableExamples:
         assert not existsEnv("unknownEnv")
 
-      return getEnvImpl(key) != nil
+      result = getEnvImpl(key) != nil
 
     proc putEnv*(key, val: string) {.tags: [WriteEnvEffect].} =
       ## Sets the value of the `environment variable`:idx: named `key` to `val`.
@@ -134,7 +142,7 @@ when not defined(nimscript):
       ## * `envPairs iterator`_
       template bail = raiseOSError(osLastError(), key)
       when defined(windows):
-        #[ 
+        #[
         # https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/putenv-s-wputenv-s?view=msvc-160
         > You can remove a variable from the environment by specifying an empty string (that is, "") for value_string
         note that nil is not legal
@@ -171,20 +179,17 @@ when not defined(nimscript):
 
     iterator envPairsImpl(): tuple[key, value: string] {.tags: [ReadEnvEffect].} =
       when defined(windows):
-        block:
-          template impl(get_fun, typ, size, zero, free_fun) =
-            let env = get_fun()
-            var e = env
-            if e == nil: break
-            while true:
-              let eend = strEnd(e)
-              let kv = $e
-              let p = find(kv, '=')
-              yield (substr(kv, 0, p-1), substr(kv, p+1))
-              e = cast[typ](cast[ByteAddress](eend)+size)
-              if typeof(zero)(eend[1]) == zero: break
-            discard free_fun(env)
-          impl(getEnvironmentStringsW, WideCString, 2, 0, freeEnvironmentStringsW)
+        let env = getEnvironmentStringsW()
+        var e = env
+        if e != nil:
+          while true:
+            let eend = strEnd(e)
+            let kv = $e
+            let p = find(kv, '=')
+            yield (substr(kv, 0, p-1), substr(kv, p+1))
+            e = cast[WideCString](cast[ByteAddress](eend)+2)
+            if int(eend[1]) == 0: break
+          discard freeEnvironmentStringsW(env)
       else:
         var i = 0
         when defined(macosx) and not defined(ios) and not defined(emscripten):
diff --git a/lib/std/exitprocs.nim b/lib/std/exitprocs.nim
index c6537f7f8..f26368f42 100644
--- a/lib/std/exitprocs.nim
+++ b/lib/std/exitprocs.nim
@@ -7,7 +7,11 @@
 #    distribution, for details about the copyright.
 #
 
-import locks
+## This module allows adding hooks to program exit.
+
+import std/locks
+when defined(js) and not defined(nodejs):
+  import std/assertions
 
 type
   FunKind = enum kClosure, kNoconv # extend as needed
@@ -18,20 +22,20 @@ type
 
 var
   gFunsLock: Lock
-  gFuns: seq[Fun]
+  gFuns {.cursor.}: seq[Fun] #Intentionally use the cursor to break up the lifetime trace and make it compatible with JS.
 
 initLock(gFunsLock)
 
 when defined(js):
   proc addAtExit(quitProc: proc() {.noconv.}) =
     when defined(nodejs):
-      asm """
+      {.emit: """
         process.on('exit', `quitProc`);
-      """
+      """.}
     elif defined(js):
-      asm """
+      {.emit: """
         window.onbeforeunload = `quitProc`;
-      """
+      """.}
 else:
   proc addAtExit(quitProc: proc() {.noconv.}) {.
     importc: "atexit", header: "<stdlib.h>".}
@@ -43,6 +47,7 @@ proc callClosures() {.noconv.} =
       case fun.kind
       of kClosure: fun.fun1()
       of kNoconv: fun.fun2()
+    gFuns.setLen(0)
 
 template fun() =
   if gFuns.len == 0:
@@ -64,24 +69,19 @@ proc addExitProc*(cl: proc() {.noconv.}) =
     fun()
     gFuns.add Fun(kind: kNoconv, fun2: cl)
 
-when not defined(nimscript):
+when not defined(nimscript) and (not defined(js) or defined(nodejs)):
   proc getProgramResult*(): int =
     when defined(js) and defined(nodejs):
-      asm """
+      {.emit: """
 `result` = process.exitCode;
-"""
-    elif not defined(js):
-      result = programResult
+""".}
     else:
-      doAssert false
+      result = programResult
 
   proc setProgramResult*(a: int) =
-    # pending https://github.com/nim-lang/Nim/issues/14674
     when defined(js) and defined(nodejs):
-      asm """
+      {.emit: """
 process.exitCode = `a`;
-"""
-    elif not defined(js):
-      programResult = a
+""".}
     else:
-      doAssert false
+      programResult = a
diff --git a/lib/std/files.nim b/lib/std/files.nim
new file mode 100644
index 000000000..c4e0491c9
--- /dev/null
+++ b/lib/std/files.nim
@@ -0,0 +1,46 @@
+## This module implements file handling.
+##
+## **See also:**
+## * `paths module <paths.html>`_ for path manipulation
+
+from std/paths import Path, ReadDirEffect, WriteDirEffect
+
+from std/private/osfiles import fileExists, removeFile,
+                                moveFile
+
+
+proc fileExists*(filename: Path): bool {.inline, tags: [ReadDirEffect], sideEffect.} =
+  ## Returns true if `filename` exists and is a regular file or symlink.
+  ##
+  ## Directories, device files, named pipes and sockets return false.
+  result = fileExists(filename.string)
+
+proc removeFile*(file: Path) {.inline, tags: [WriteDirEffect].} =
+  ## Removes the `file`.
+  ##
+  ## If this fails, `OSError` is raised. This does not fail
+  ## if the file never existed in the first place.
+  ##
+  ## On Windows, ignores the read-only attribute.
+  ##
+  ## See also:
+  ## * `removeDir proc <dirs.html#removeDir>`_
+  ## * `moveFile proc`_
+  removeFile(file.string)
+
+proc moveFile*(source, dest: Path) {.inline,
+    tags: [ReadDirEffect, ReadIOEffect, WriteIOEffect].} =
+  ## Moves a file from `source` to `dest`.
+  ##
+  ## Symlinks are not followed: if `source` is a symlink, it is itself moved,
+  ## not its target.
+  ##
+  ## If this fails, `OSError` is raised.
+  ## If `dest` already exists, it will be overwritten.
+  ##
+  ## Can be used to `rename files`:idx:.
+  ##
+  ## See also:
+  ## * `moveDir proc <dirs.html#moveDir>`_
+  ## * `removeFile proc`_
+  moveFile(source.string, dest.string)
diff --git a/lib/std/formatfloat.nim b/lib/std/formatfloat.nim
index 6f2383760..9258245f6 100644
--- a/lib/std/formatfloat.nim
+++ b/lib/std/formatfloat.nim
@@ -7,10 +7,10 @@
 #    distribution, for details about the copyright.
 #
 
+## This module implements formatting floats as strings.
+
 when defined(nimPreviewSlimSystem):
   import std/assertions
-else:
-  {.deprecated: "formatfloat is about to move out of system; use `-d:nimPreviewSlimSystem` and import `std/formatfloat`".}
 
 proc c_memcpy(a, b: pointer, size: csize_t): pointer {.importc: "memcpy", header: "<string.h>", discardable.}
 
@@ -28,15 +28,15 @@ proc writeFloatToBufferRoundtrip*(buf: var array[65, char]; value: BiggestFloat)
   ##
   ## returns the amount of bytes written to `buf` not counting the
   ## terminating '\0' character.
-  result = toChars(buf, value, forceTrailingDotZero=true)
+  result = toChars(buf, value, forceTrailingDotZero=true).int
   buf[result] = '\0'
 
 proc writeFloatToBufferRoundtrip*(buf: var array[65, char]; value: float32): int =
-  result = float32ToChars(buf, value, forceTrailingDotZero=true)
+  result = float32ToChars(buf, value, forceTrailingDotZero=true).int
   buf[result] = '\0'
 
-proc c_sprintf(buf, frmt: cstring): cint {.header: "<stdio.h>",
-                                    importc: "sprintf", varargs, noSideEffect.}
+proc c_snprintf(buf: cstring, n: csize_t, frmt: cstring): cint {.header: "<stdio.h>",
+                                    importc: "snprintf", varargs, noSideEffect.}
 
 proc writeToBuffer(buf: var array[65, char]; value: cstring) =
   var i = 0
@@ -49,7 +49,7 @@ proc writeFloatToBufferSprintf*(buf: var array[65, char]; value: BiggestFloat):
   ##
   ## returns the amount of bytes written to `buf` not counting the
   ## terminating '\0' character.
-  var n: int = c_sprintf(addr buf, "%.16g", value)
+  var n = c_snprintf(cast[cstring](addr buf), 65, "%.16g", value).int
   var hasDot = false
   for i in 0..n-1:
     if buf[i] == ',':
@@ -86,36 +86,37 @@ proc writeFloatToBuffer*(buf: var array[65, char]; value: BiggestFloat | float32
 
 proc addFloatRoundtrip*(result: var string; x: float | float32) =
   when nimvm:
-    doAssert false
+    raiseAssert "unreachable"
   else:
     var buffer {.noinit.}: array[65, char]
     let n = writeFloatToBufferRoundtrip(buffer, x)
-    result.addCstringN(cstring(buffer[0].addr), n)
+    result.addCstringN(cast[cstring](buffer[0].addr), n)
 
 proc addFloatSprintf*(result: var string; x: float) =
   when nimvm:
-    doAssert false
+    raiseAssert "unreachable"
   else:
     var buffer {.noinit.}: array[65, char]
     let n = writeFloatToBufferSprintf(buffer, x)
-    result.addCstringN(cstring(buffer[0].addr), n)
-
-proc nimFloatToString(a: float): cstring =
-  ## ensures the result doesn't print like an integer, i.e. return 2.0, not 2
-  # print `-0.0` properly
-  asm """
-    function nimOnlyDigitsOrMinus(n) {
-      return n.toString().match(/^-?\d+$/);
-    }
-    if (Number.isSafeInteger(`a`))
-      `result` = `a` === 0 && 1 / `a` < 0 ? "-0.0" : `a`+".0"
-    else {
-      `result` = `a`+""
-      if(nimOnlyDigitsOrMinus(`result`)){
-        `result` = `a`+".0"
+    result.addCstringN(cast[cstring](buffer[0].addr), n)
+
+when defined(js):
+  proc nimFloatToString(a: float): cstring =
+    ## ensures the result doesn't print like an integer, i.e. return 2.0, not 2
+    # print `-0.0` properly
+    {.emit: """
+      function nimOnlyDigitsOrMinus(n) {
+        return n.toString().match(/^-?\d+$/);
+      }
+      if (Number.isSafeInteger(`a`))
+        `result` = `a` === 0 && 1 / `a` < 0 ? "-0.0" : `a`+".0";
+      else {
+        `result` = `a`+"";
+        if(nimOnlyDigitsOrMinus(`result`)){
+          `result` = `a`+".0";
+        }
       }
-    }
-  """
+    """.}
 
 proc addFloat*(result: var string; x: float | float32) {.inline.} =
   ## Converts float to its string representation and appends it to `result`.
diff --git a/lib/std/genasts.nim b/lib/std/genasts.nim
index c5f51e5d9..d0f07c527 100644
--- a/lib/std/genasts.nim
+++ b/lib/std/genasts.nim
@@ -1,4 +1,6 @@
-import macros
+## This module implements AST generation using captured variables for macros.
+
+import std/macros
 
 type GenAstOpt* = enum
   kDirtyTemplate,
@@ -22,7 +24,7 @@ macro genAstOpt*(options: static set[GenAstOpt], args: varargs[untyped]): untype
       result = genAst(cond, s = repr(cond), lhs = cond[1], rhs = cond[2]):
         # each local symbol we access must be explicitly captured
         if not cond:
-          doAssert false, "'$#'' failed: lhs: '$#', rhs: '$#'" % [s, $lhs, $rhs]
+          raiseAssert "'$#'' failed: lhs: '$#', rhs: '$#'" % [s, $lhs, $rhs]
     let a = 3
     check2 a*2 == a+3
     if false: check2 a*2 < a+1 # would error with: 'a * 2 < a + 1'' failed: lhs: '6', rhs: '4'
diff --git a/lib/std/isolation.nim b/lib/std/isolation.nim
index 7d6ac6092..b03e00651 100644
--- a/lib/std/isolation.nim
+++ b/lib/std/isolation.nim
@@ -15,7 +15,7 @@
 ##
 
 type
-  Isolated*[T] = object ## Isolated data can only be moved, not copied.
+  Isolated*[T] {.sendable.} = object ## Isolated data can only be moved, not copied.
     value: T
 
 proc `=copy`*[T](dest: var Isolated[T]; src: Isolated[T]) {.error.}
@@ -38,9 +38,9 @@ func isolate*[T](value: sink T): Isolated[T] {.magic: "Isolate".} =
 
 func unsafeIsolate*[T](value: sink T): Isolated[T] =
   ## Creates an isolated subgraph from the expression `value`.
-  ## 
+  ##
   ## .. warning:: The proc doesn't check whether `value` is isolated.
-  ## 
+  ##
   Isolated[T](value: value)
 
 func extract*[T](src: var Isolated[T]): T =
diff --git a/lib/std/jsbigints.nim b/lib/std/jsbigints.nim
index 04578fc87..4e996ea7b 100644
--- a/lib/std/jsbigints.nim
+++ b/lib/std/jsbigints.nim
@@ -14,7 +14,7 @@ func big*(integer: SomeInteger): JsBigInt {.importjs: "BigInt(#)".} =
   runnableExamples:
     doAssert big(1234567890) == big"1234567890"
     doAssert 0b1111100111.big == 0o1747.big and 0o1747.big == 999.big
-  when nimvm: doAssert false, "JsBigInt can not be used at compile-time nor static context" else: discard
+  when nimvm: raiseAssert "JsBigInt can not be used at compile-time nor static context" else: discard
 
 func `'big`*(num: cstring): JsBigInt {.importjs: "BigInt(#)".} =
   ## Constructor for `JsBigInt`.
@@ -28,11 +28,11 @@ func `'big`*(num: cstring): JsBigInt {.importjs: "BigInt(#)".} =
     doAssert 0xdeadbeaf'big == 0xdeadbeaf.big
     doAssert 0xffffffffffffffff'big == (1'big shl 64'big) - 1'big
     doAssert not compiles(static(12'big))
-  when nimvm: doAssert false, "JsBigInt can not be used at compile-time nor static context" else: discard
+  when nimvm: raiseAssert "JsBigInt can not be used at compile-time nor static context" else: discard
 
 func big*(integer: cstring): JsBigInt {.importjs: "BigInt(#)".} =
   ## Alias for `'big`
-  when nimvm: doAssert false, "JsBigInt can not be used at compile-time nor static context" else: discard
+  when nimvm: raiseAssert "JsBigInt can not be used at compile-time nor static context" else: discard
 
 func toCstring*(this: JsBigInt; radix: 2..36): cstring {.importjs: "#.toString(#)".} =
   ## Converts from `JsBigInt` to `cstring` representation.
@@ -64,10 +64,10 @@ func wrapToUint*(this: JsBigInt; bits: Natural): JsBigInt {.importjs:
   runnableExamples:
     doAssert (big("3") + big("2") ** big("66")).wrapToUint(66) == big("3")
 
-func toNumber*(this: JsBigInt): BiggestInt {.importjs: "Number(#)".} =
+func toNumber*(this: JsBigInt): int {.importjs: "Number(#)".} =
   ## Does not do any bounds check and may or may not return an inexact representation.
   runnableExamples:
-    doAssert toNumber(big"2147483647") == 2147483647.BiggestInt
+    doAssert toNumber(big"2147483647") == 2147483647.int
 
 func `+`*(x, y: JsBigInt): JsBigInt {.importjs: "(# $1 #)".} =
   runnableExamples:
@@ -110,7 +110,7 @@ func `==`*(x, y: JsBigInt): bool {.importjs: "(# == #)".} =
     doAssert big"42" == big"42"
 
 func `**`*(x, y: JsBigInt): JsBigInt {.importjs: "((#) $1 #)".} =
-  # (#) needed, refs https://github.com/nim-lang/Nim/pull/16409#issuecomment-760550812
+  # (#) needed due to unary minus
   runnableExamples:
     doAssert big"2" ** big"64" == big"18446744073709551616"
     doAssert big"-2" ** big"3" == big"-8"
@@ -120,8 +120,6 @@ func `**`*(x, y: JsBigInt): JsBigInt {.importjs: "((#) $1 #)".} =
     try: discard big"2" ** big"-1" # raises foreign `RangeError`
     except: ok = true
     doAssert ok
-  # pending https://github.com/nim-lang/Nim/pull/15940, simplify to:
-  # doAssertRaises: discard big"2" ** big"-1" # raises foreign `RangeError`
 
 func `and`*(x, y: JsBigInt): JsBigInt {.importjs: "(# & #)".} =
   runnableExamples:
diff --git a/lib/std/jsfetch.nim b/lib/std/jsfetch.nim
index 7fe154325..219594619 100644
--- a/lib/std/jsfetch.nim
+++ b/lib/std/jsfetch.nim
@@ -2,7 +2,8 @@
 when not defined(js):
   {.fatal: "Module jsfetch is designed to be used with the JavaScript backend.".}
 
-import std/[asyncjs, jsheaders, jsformdata]
+import std/[asyncjs, jsformdata, jsheaders]
+export jsformdata, jsheaders
 from std/httpcore import HttpMethod
 from std/jsffi import JsObject
 
@@ -84,9 +85,9 @@ proc unsafeNewFetchOptions*(metod, body, mode, credentials, cache, referrerPolic
     "{method: #, body: #, mode: #, credentials: #, cache: #, referrerPolicy: #, keepalive: #, redirect: #, referrer: #, integrity: #, headers: #}".}
   ## .. warning:: Unsafe `newfetchOptions`.
 
-func newfetchOptions*(metod: HttpMethod; body: cstring;
-    mode: FetchModes; credentials: FetchCredentials; cache: FetchCaches; referrerPolicy: FetchReferrerPolicies;
-    keepalive: bool; redirect = frFollow; referrer = "client".cstring; integrity = "".cstring,
+func newfetchOptions*(metod = HttpGet; body: cstring = nil;
+    mode = fmCors; credentials = fcSameOrigin; cache = fchDefault; referrerPolicy = frpNoReferrerWhenDowngrade;
+    keepalive = false; redirect = frFollow; referrer = "client".cstring; integrity = "".cstring,
     headers: Headers = newHeaders()): FetchOptions =
   ## Constructor for `FetchOptions`.
   result = FetchOptions(
@@ -116,7 +117,7 @@ func `$`*(self: Request | Response | FetchOptions): string = $toCstring(self)
 
 
 runnableExamples("-r:off"):
-  import std/[asyncjs, jsconsole, jsheaders, jsformdata]
+  import std/[asyncjs, jsconsole, jsformdata, jsheaders]
   from std/httpcore import HttpMethod
   from std/jsffi import JsObject
   from std/sugar import `=>`
diff --git a/lib/std/jsformdata.nim b/lib/std/jsformdata.nim
index 120f8742d..61dcc39a3 100644
--- a/lib/std/jsformdata.nim
+++ b/lib/std/jsformdata.nim
@@ -2,17 +2,21 @@
 when not defined(js):
   {.fatal: "Module jsformdata is designed to be used with the JavaScript backend.".}
 
+from std/dom import Blob
+
 type FormData* = ref object of JsRoot ## FormData API.
 
 func newFormData*(): FormData {.importjs: "new FormData()".}
 
-func add*(self: FormData; name: cstring; value: SomeNumber | bool | cstring) {.importjs: "#.append(#, #)".}
+func add*(self: FormData; name: cstring; value: SomeNumber | bool | cstring | Blob) {.importjs: "#.append(#, #)".}
   ## https://developer.mozilla.org/en-US/docs/Web/API/FormData/append
-  ## Duplicate keys are allowed and order is preserved.
+  ##
+  ## .. hint:: Duplicate keys are allowed and order is preserved.
 
-func add*(self: FormData; name: cstring; value: SomeNumber | bool | cstring, filename: cstring) {.importjs: "#.append(#, #, #)".}
+func add*(self: FormData; name: cstring; value: SomeNumber | bool | cstring | Blob; filename: cstring) {.importjs: "#.append(#, #, #)".}
   ## https://developer.mozilla.org/en-US/docs/Web/API/FormData/append
-  ## Duplicate keys are allowed and order is preserved.
+  ##
+  ## .. hint:: Duplicate keys are allowed and order is preserved.
 
 func delete*(self: FormData; name: cstring) {.importjs: "#.$1(#)".}
   ## https://developer.mozilla.org/en-US/docs/Web/API/FormData/delete
@@ -34,10 +38,10 @@ func values*(self: FormData): seq[cstring] {.importjs: "Array.from(#.$1())".}
 func pairs*(self: FormData): seq[tuple[key, val: cstring]] {.importjs: "Array.from(#.entries())".}
   ## https://developer.mozilla.org/en-US/docs/Web/API/FormData/entries
 
-func put*(self: FormData; name, value, filename: cstring) {.importjs: "#.set(#, #, #)".}
+func put*(self: FormData; name: cstring; value: SomeNumber | bool | cstring | Blob; filename: cstring) {.importjs: "#.set(#, #, #)".}
   ## https://developer.mozilla.org/en-US/docs/Web/API/FormData/set
 
-func `[]=`*(self: FormData; name, value: cstring) {.importjs: "#.set(#, #)".}
+func `[]=`*(self: FormData; name: cstring; value: SomeNumber | bool | cstring | Blob) {.importjs: "#.set(#, #)".}
   ## https://developer.mozilla.org/en-US/docs/Web/API/FormData/set
 
 func `[]`*(self: FormData; name: cstring): cstring {.importjs: "#.get(#)".}
diff --git a/lib/std/jsonutils.nim b/lib/std/jsonutils.nim
index 722ea49b5..2d28748ce 100644
--- a/lib/std/jsonutils.nim
+++ b/lib/std/jsonutils.nim
@@ -1,5 +1,5 @@
 ##[
-This module implements a hookable (de)serialization for arbitrary types.
+This module implements a hookable (de)serialization for arbitrary types using JSON.
 Design goal: avoid importing modules where a custom serialization is needed;
 see strtabs.fromJsonHook,toJsonHook for an example.
 ]##
@@ -16,7 +16,7 @@ runnableExamples:
   assert 0.0.toJson.kind == JFloat
   assert Inf.toJson.kind == JString
 
-import json, strutils, tables, sets, strtabs, options
+import std/[json, strutils, tables, sets, strtabs, options, strformat]
 
 #[
 Future directions:
@@ -30,29 +30,15 @@ add a way to customize serialization, for e.g.:
   objects.
 ]#
 
-import macros
-from enumutils import symbolName
-from typetraits import OrdinalEnum
+import std/macros
+from std/enumutils import symbolName
+from std/typetraits import OrdinalEnum, tupleLen
 
 when defined(nimPreviewSlimSystem):
   import std/assertions
 
-when not defined(nimFixedForwardGeneric):
-  # xxx remove pending csources_v1 update >= 1.2.0
-  proc to[T](node: JsonNode, t: typedesc[T]): T =
-    when T is string: node.getStr
-    elif T is bool: node.getBool
-    else: static: doAssert false, $T # support as needed (only needed during bootstrap)
-  proc isNamedTuple(T: typedesc): bool = # old implementation
-    when T isnot tuple: result = false
-    else:
-      var t: T
-      for name, _ in t.fieldPairs:
-        when name == "Field0": return compiles(t.Field0)
-        else: return true
-      return false
-else:
-  proc isNamedTuple(T: typedesc): bool {.magic: "TypeTrait".}
+
+proc isNamedTuple(T: typedesc): bool {.magic: "TypeTrait".}
 
 type
   Joptions* = object # xxx rename FromJsonOptions
@@ -92,19 +78,24 @@ macro getDiscriminants(a: typedesc): seq[string] =
   let sym = a[1]
   let t = sym.getTypeImpl
   let t2 = t[2]
-  doAssert t2.kind == nnkRecList
-  result = newTree(nnkBracket)
-  for ti in t2:
-    if ti.kind == nnkRecCase:
-      let key = ti[0][0]
-      let typ = ti[0][1]
-      result.add newLit key.strVal
-  if result.len > 0:
+  case t2.kind
+  of nnkEmpty: # allow empty objects
     result = quote do:
-      @`result`
+        seq[string].default
+  of nnkRecList:
+    result = newTree(nnkBracket)
+    for ti in t2:
+      if ti.kind == nnkRecCase:
+        let key = ti[0][0]
+        result.add newLit key.strVal
+    if result.len > 0:
+      result = quote do:
+        @`result`
+    else:
+      result = quote do:
+        seq[string].default
   else:
-    result = quote do:
-      seq[string].default
+    raiseAssert "unexpected kind: " & $t2.kind
 
 macro initCaseObject(T: typedesc, fun: untyped): untyped =
   ## does the minimum to construct a valid case object, only initializing
@@ -118,7 +109,7 @@ macro initCaseObject(T: typedesc, fun: untyped): untyped =
   case t.kind
   of nnkObjectTy: t2 = t[2]
   of nnkRefTy: t2 = t[0].getTypeImpl[2]
-  else: doAssert false, $t.kind # xxx `nnkPtrTy` could be handled too
+  else: raiseAssert $t.kind # xxx `nnkPtrTy` could be handled too
   doAssert t2.kind == nnkRecList
   result = newTree(nnkObjConstr)
   result.add sym
@@ -168,7 +159,7 @@ template fromJsonFields(newObj, oldObj, json, discKeys, opt) =
           if discKeys.len == 0 or hasField(oldObj, key):
             val = accessField(oldObj, key)
       else:
-        checkJson false, $($T, key, json)
+        checkJson false, "key '$1' for $2 not in $3" % [key, $T, json.pretty()]
     else:
       if json.hasKey key:
         numMatched.inc
@@ -187,7 +178,7 @@ template fromJsonFields(newObj, oldObj, json, discKeys, opt) =
     else:
       json.len == num and num == numMatched
 
-  checkJson ok, $(json.len, num, numMatched, $T, json)
+  checkJson ok, "There were $1 keys (expecting $2) for $3 with $4" % [$json.len, $num, $T, json.pretty()]
 
 proc fromJson*[T](a: var T, b: JsonNode, opt = Joptions())
 
@@ -220,28 +211,24 @@ proc fromJson*[T](a: var T, b: JsonNode, opt = Joptions()) =
   adding "json path" leading to `b` can be added in future work.
   ]#
   checkJson b != nil, $($T, b)
-  when compiles(fromJsonHook(a, b)): fromJsonHook(a, b)
+  when compiles(fromJsonHook(a, b, opt)): fromJsonHook(a, b, opt)
+  elif compiles(fromJsonHook(a, b)): fromJsonHook(a, b)
   elif T is bool: a = to(b,T)
   elif T is enum:
     case b.kind
     of JInt: a = T(b.getBiggestInt())
     of JString: a = parseEnum[T](b.getStr())
-    else: checkJson false, $($T, " ", b)
+    else: checkJson false, fmt"Expecting int/string for {$T} got {b.pretty()}"
   elif T is uint|uint64: a = T(to(b, uint64))
   elif T is Ordinal: a = cast[T](to(b, int))
   elif T is pointer: a = cast[pointer](to(b, int))
-  elif T is distinct:
-    when nimvm:
-      # bug, potentially related to https://github.com/nim-lang/Nim/issues/12282
-      a = T(jsonTo(b, distinctBase(T)))
-    else:
-      a.distinctBase.fromJson(b)
+  elif T is distinct: a.distinctBase.fromJson(b)
   elif T is string|SomeNumber: a = to(b,T)
   elif T is cstring:
     case b.kind
     of JNull: a = nil
     of JString: a = b.str
-    else: checkJson false, $($T, " ", b)
+    else: checkJson false, fmt"Expecting null/string for {$T} got {b.pretty()}"
   elif T is JsonNode: a = b
   elif T is ref | ptr:
     if b.kind == JNull: a = nil
@@ -249,7 +236,7 @@ proc fromJson*[T](a: var T, b: JsonNode, opt = Joptions()) =
       a = T()
       fromJson(a[], b, opt)
   elif T is array:
-    checkJson a.len == b.len, $(a.len, b.len, $T)
+    checkJson a.len == b.len, fmt"Json array size doesn't match for {$T}"
     var i = 0
     for ai in mitems(a):
       fromJson(ai, b[i], opt)
@@ -285,14 +272,24 @@ proc fromJson*[T](a: var T, b: JsonNode, opt = Joptions()) =
       fromJsonFields(a, nil, b, seq[string].default, opt)
     else:
       checkJson b.kind == JArray, $(b.kind) # we could customize whether to allow JNull
+
+      when compiles(tupleLen(T)):
+        let tupleSize = tupleLen(T)
+      else:
+        # Tuple len isn't in csources_v1 so using tupleLen would fail.
+        # Else branch basically never runs (tupleLen added in 1.1 and jsonutils in 1.4), but here for consistency
+        var tupleSize = 0
+        for val in fields(a):
+          tupleSize.inc
+
+      checkJson b.len == tupleSize, fmt"Json doesn't match expected length of {tupleSize}, got {b.pretty()}"
       var i = 0
       for val in fields(a):
         fromJson(val, b[i], opt)
         i.inc
-      checkJson b.len == i, $(b.len, i, $T, b) # could customize
   else:
     # checkJson not appropriate here
-    static: doAssert false, "not yet implemented: " & $T
+    static: raiseAssert "not yet implemented: " & $T
 
 proc jsonTo*(b: JsonNode, T: typedesc, opt = Joptions()): T =
   ## reverse of `toJson`
@@ -305,7 +302,8 @@ proc toJson*[T](a: T, opt = initToJsonOptions()): JsonNode =
   ## .. note:: With `-d:nimPreviewJsonutilsHoleyEnum`, `toJson` now can 
   ##    serialize/deserialize holey enums as regular enums (via `ord`) instead of as strings.
   ##    It is expected that this behavior becomes the new default in upcoming versions.
-  when compiles(toJsonHook(a)): result = toJsonHook(a)
+  when compiles(toJsonHook(a, opt)): result = toJsonHook(a, opt)
+  elif compiles(toJsonHook(a)): result = toJsonHook(a)
   elif T is object | tuple:
     when T is object or isNamedTuple(T):
       result = newJObject()
@@ -348,7 +346,7 @@ proc toJson*[T](a: T, opt = initToJsonOptions()): JsonNode =
   else: result = %a
 
 proc fromJsonHook*[K: string|cstring, V](t: var (Table[K, V] | OrderedTable[K, V]),
-                         jsonNode: JsonNode) =
+                         jsonNode: JsonNode, opt = Joptions()) =
   ## Enables `fromJson` for `Table` and `OrderedTable` types.
   ##
   ## See also:
@@ -366,14 +364,13 @@ proc fromJsonHook*[K: string|cstring, V](t: var (Table[K, V] | OrderedTable[K, V
           "type is `" & $jsonNode.kind & "`."
   clear(t)
   for k, v in jsonNode:
-    t[k] = jsonTo(v, V)
+    t[k] = jsonTo(v, V, opt)
 
-proc toJsonHook*[K: string|cstring, V](t: (Table[K, V] | OrderedTable[K, V])): JsonNode =
+proc toJsonHook*[K: string|cstring, V](t: (Table[K, V] | OrderedTable[K, V]), opt = initToJsonOptions()): JsonNode =
   ## Enables `toJson` for `Table` and `OrderedTable` types.
   ##
   ## See also:
   ## * `fromJsonHook proc<#fromJsonHook,,JsonNode>`_
-  # pending PR #9217 use: toSeq(a) instead of `collect` in `runnableExamples`.
   runnableExamples:
     import std/[tables, json, sugar]
     let foo = (
@@ -388,9 +385,9 @@ proc toJsonHook*[K: string|cstring, V](t: (Table[K, V] | OrderedTable[K, V])): J
   result = newJObject()
   for k, v in pairs(t):
     # not sure if $k has overhead for string
-    result[(when K is string: k else: $k)] = toJson(v)
+    result[(when K is string: k else: $k)] = toJson(v, opt)
 
-proc fromJsonHook*[A](s: var SomeSet[A], jsonNode: JsonNode) =
+proc fromJsonHook*[A](s: var SomeSet[A], jsonNode: JsonNode, opt = Joptions()) =
   ## Enables `fromJson` for `HashSet` and `OrderedSet` types.
   ##
   ## See also:
@@ -408,9 +405,9 @@ proc fromJsonHook*[A](s: var SomeSet[A], jsonNode: JsonNode) =
           "type is `" & $jsonNode.kind & "`."
   clear(s)
   for v in jsonNode:
-    incl(s, jsonTo(v, A))
+    incl(s, jsonTo(v, A, opt))
 
-proc toJsonHook*[A](s: SomeSet[A]): JsonNode =
+proc toJsonHook*[A](s: SomeSet[A], opt = initToJsonOptions()): JsonNode =
   ## Enables `toJson` for `HashSet` and `OrderedSet` types.
   ##
   ## See also:
@@ -422,9 +419,9 @@ proc toJsonHook*[A](s: SomeSet[A]): JsonNode =
 
   result = newJArray()
   for k in s:
-    add(result, toJson(k))
+    add(result, toJson(k, opt))
 
-proc fromJsonHook*[T](self: var Option[T], jsonNode: JsonNode) =
+proc fromJsonHook*[T](self: var Option[T], jsonNode: JsonNode, opt = Joptions()) =
   ## Enables `fromJson` for `Option` types.
   ##
   ## See also:
@@ -438,11 +435,11 @@ proc fromJsonHook*[T](self: var Option[T], jsonNode: JsonNode) =
     assert isNone(opt)
 
   if jsonNode.kind != JNull:
-    self = some(jsonTo(jsonNode, T))
+    self = some(jsonTo(jsonNode, T, opt))
   else:
     self = none[T]()
 
-proc toJsonHook*[T](self: Option[T]): JsonNode =
+proc toJsonHook*[T](self: Option[T], opt = initToJsonOptions()): JsonNode =
   ## Enables `toJson` for `Option` types.
   ##
   ## See also:
@@ -455,7 +452,7 @@ proc toJsonHook*[T](self: Option[T]): JsonNode =
     assert $toJson(optNone) == "null"
 
   if isSome(self):
-    toJson(get(self))
+    toJson(get(self), opt)
   else:
     newJNull()
 
diff --git a/lib/std/monotimes.nim b/lib/std/monotimes.nim
index 5c67a5d4c..bf6dc776b 100644
--- a/lib/std/monotimes.nim
+++ b/lib/std/monotimes.nim
@@ -36,7 +36,7 @@ See also
 * `times module <times.html>`_
 ]##
 
-import times
+import std/times
 
 type
   MonoTime* = object ## Represents a monotonic timestamp.
@@ -74,7 +74,7 @@ when defined(js):
   {.pop.}
 
 elif defined(posix) and not defined(osx):
-  import posix
+  import std/posix
 
 when defined(zephyr):
   proc k_uptime_ticks(): int64 {.importc: "k_uptime_ticks", header: "<kernel.h>".}
diff --git a/lib/std/objectdollar.nim b/lib/std/objectdollar.nim
index f413bbc46..86ce9afc8 100644
--- a/lib/std/objectdollar.nim
+++ b/lib/std/objectdollar.nim
@@ -1,3 +1,5 @@
+## This module implements a generic `$` operator to convert objects to strings.
+
 import std/private/miscdollars
 
 proc `$`*[T: object](x: T): string =
diff --git a/lib/std/oserrors.nim b/lib/std/oserrors.nim
index 9c2649eab..7b11c5e8e 100644
--- a/lib/std/oserrors.nim
+++ b/lib/std/oserrors.nim
@@ -15,7 +15,9 @@ type
 
 when not defined(nimscript):
   when defined(windows):
-    import winlean
+    import std/winlean
+    when defined(nimPreviewSlimSystem):
+      import std/widestrs
   else:
     var errno {.importc, header: "<errno.h>".}: cint
 
@@ -73,17 +75,14 @@ proc newOSError*(
   ## See also:
   ## * `osErrorMsg proc`_
   ## * `osLastError proc`_
-  var e: owned(ref OSError); new(e)
-  e.errorCode = errorCode.int32
-  e.msg = osErrorMsg(errorCode)
+  result = (ref OSError)(errorCode: errorCode.int32, msg: osErrorMsg(errorCode))
   if additionalInfo.len > 0:
-    if e.msg.len > 0 and e.msg[^1] != '\n': e.msg.add '\n'
-    e.msg.add "Additional info: "
-    e.msg.add additionalInfo
+    if result.msg.len > 0 and result.msg[^1] != '\n': result.msg.add '\n'
+    result.msg.add "Additional info: "
+    result.msg.add additionalInfo
       # don't add trailing `.` etc, which negatively impacts "jump to file" in IDEs.
-  if e.msg == "":
-    e.msg = "unknown OS error"
-  return e
+  if result.msg == "":
+    result.msg = "unknown OS error"
 
 proc raiseOSError*(errorCode: OSErrorCode, additionalInfo = "") {.noinline.} =
   ## Raises an `OSError exception <system.html#OSError>`_.
diff --git a/lib/std/outparams.nim b/lib/std/outparams.nim
new file mode 100644
index 000000000..a471fbaa7
--- /dev/null
+++ b/lib/std/outparams.nim
@@ -0,0 +1,38 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2022 Nim contributors
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+## `outParamsAt` macro for easy writing code that works with both 2.0 and 1.x.
+
+import std/macros
+
+macro outParamsAt*(positions: static openArray[int]; n: untyped): untyped =
+  ## Use this macro to annotate `out` parameters in a portable way.
+  runnableExamples:
+    proc p(x: var int) {.outParamsAt: [1].} =
+      discard "x is really an 'out int' if the Nim compiler supports 'out' parameters"
+
+  result = n
+  when defined(nimHasOutParams):
+    var p = n.params
+    for po in positions:
+      p[po][^2].expectKind nnkVarTy
+      p[po][^2] = newTree(nnkOutTy, p[po][^2][0])
+
+when isMainModule:
+  {.experimental: "strictDefs".}
+
+  proc main(x: var int) {.outParamsAt: [1].} =
+    x = 3
+
+  proc us =
+    var x: int
+    main x
+    echo x
+
+  us()
diff --git a/lib/std/packedsets.nim b/lib/std/packedsets.nim
index 1e2892658..3320558f2 100644
--- a/lib/std/packedsets.nim
+++ b/lib/std/packedsets.nim
@@ -12,17 +12,12 @@
 ##
 ## Supports any Ordinal type.
 ##
-## .. note:: Currently the assignment operator `=` for `PackedSet[A]`
-##   performs some rather meaningless shallow copy. Since Nim currently does
-##   not allow the assignment operator to be overloaded, use the `assign proc
-##   <#assign,PackedSet[A],PackedSet[A]>`_ to get a deep copy.
-##
 ## See also
 ## ========
 ## * `sets module <sets.html>`_ for more general hash sets
 
 import std/private/since
-import hashes
+import std/hashes
 
 when defined(nimPreviewSlimSystem):
   import std/assertions
@@ -114,7 +109,6 @@ proc intSetPut[A](t: var PackedSet[A], key: int): Trunk =
   t.data[h] = result
 
 proc bitincl[A](s: var PackedSet[A], key: int) {.inline.} =
-  var ret: Trunk
   var t = intSetPut(s, key shr TrunkShift)
   var u = key and TrunkMask
   t.bits[u shr IntShift] = t.bits[u shr IntShift] or
@@ -204,6 +198,7 @@ proc contains*[A](s: PackedSet[A], key: A): bool =
     assert B notin letters
 
   if s.elems <= s.a.len:
+    result = false
     for i in 0..<s.elems:
       if s.a[i] == ord(key): return true
   else:
@@ -412,18 +407,9 @@ proc isNil*[A](x: PackedSet[A]): bool {.inline.} =
 
   x.head.isNil and x.elems == 0
 
-proc assign*[A](dest: var PackedSet[A], src: PackedSet[A]) =
+proc `=copy`*[A](dest: var PackedSet[A], src: PackedSet[A]) =
   ## Copies `src` to `dest`.
   ## `dest` does not need to be initialized by the `initPackedSet proc <#initPackedSet>`_.
-  runnableExamples:
-    var
-      a = initPackedSet[int]()
-      b = initPackedSet[int]()
-    b.incl(5)
-    b.incl(7)
-    a.assign(b)
-    assert len(a) == 2
-
   if src.elems <= src.a.len:
     dest.data = @[]
     dest.max = 0
@@ -452,6 +438,19 @@ proc assign*[A](dest: var PackedSet[A], src: PackedSet[A]) =
       dest.data[h] = n
       it = it.next
 
+proc assign*[A](dest: var PackedSet[A], src: PackedSet[A]) {.inline, deprecated.} =
+  ## Copies `src` to `dest`.
+  ## `dest` does not need to be initialized by the `initPackedSet proc <#initPackedSet>`_.
+  runnableExamples:
+    var
+      a = initPackedSet[int]()
+      b = initPackedSet[int]()
+    b.incl(5)
+    b.incl(7)
+    a.assign(b)
+    assert len(a) == 2
+  `=copy`(dest, src)
+
 proc union*[A](s1, s2: PackedSet[A]): PackedSet[A] =
   ## Returns the union of the sets `s1` and `s2`.
   ##
diff --git a/lib/std/paths.nim b/lib/std/paths.nim
new file mode 100644
index 000000000..664dedd31
--- /dev/null
+++ b/lib/std/paths.nim
@@ -0,0 +1,302 @@
+## This module implements path handling.
+##
+## **See also:**
+## * `files module <files.html>`_ for file access
+
+import std/private/osseps
+export osseps
+
+import std/envvars
+import std/private/osappdirs
+
+import std/[pathnorm, hashes, sugar, strutils]
+
+from std/private/ospaths2 import  joinPath, splitPath,
+                                  ReadDirEffect, WriteDirEffect,
+                                  isAbsolute, relativePath,
+                                  normalizePathEnd, isRelativeTo, parentDir,
+                                  tailDir, isRootDir, parentDirs, `/../`,
+                                  extractFilename, lastPathPart,
+                                  changeFileExt, addFileExt, cmpPaths, splitFile,
+                                  unixToNativePath, absolutePath, normalizeExe,
+                                  normalizePath
+export ReadDirEffect, WriteDirEffect
+
+type
+  Path* = distinct string
+
+func hash*(x: Path): Hash =
+  let x = x.string.dup(normalizePath)
+  if FileSystemCaseSensitive:
+    result = x.hash
+  else:
+    result = x.toLowerAscii.hash
+
+template `$`*(x: Path): string =
+  string(x)
+
+func `==`*(x, y: Path): bool {.inline.} =
+  ## Compares two paths.
+  ##
+  ## On a case-sensitive filesystem this is done
+  ## case-sensitively otherwise case-insensitively.
+  result = cmpPaths(x.string, y.string) == 0
+
+template endsWith(a: string, b: set[char]): bool =
+  a.len > 0 and a[^1] in b
+
+func add(x: var string, tail: string) =
+  var state = 0
+  let trailingSep = tail.endsWith({DirSep, AltSep}) or tail.len == 0 and x.endsWith({DirSep, AltSep})
+  normalizePathEnd(x, trailingSep=false)
+  addNormalizePath(tail, x, state, DirSep)
+  normalizePathEnd(x, trailingSep=trailingSep)
+
+func add*(x: var Path, y: Path) {.borrow.}
+
+func `/`*(head, tail: Path): Path {.inline.} =
+  ## Joins two directory names to one.
+  ##
+  ## returns normalized path concatenation of `head` and `tail`, preserving
+  ## whether or not `tail` has a trailing slash (or, if tail if empty, whether
+  ## head has one).
+  ##
+  ## See also:
+  ## * `splitPath proc`_
+  ## * `uri.combine proc <uri.html#combine,Uri,Uri>`_
+  ## * `uri./ proc <uri.html#/,Uri,string>`_
+  Path(joinPath(head.string, tail.string))
+
+func splitPath*(path: Path): tuple[head, tail: Path] {.inline.} =
+  ## Splits a directory into `(head, tail)` tuple, so that
+  ## ``head / tail == path`` (except for edge cases like "/usr").
+  ##
+  ## See also:
+  ## * `add proc`_
+  ## * `/ proc`_
+  ## * `/../ proc`_
+  ## * `relativePath proc`_
+  let res = splitPath(path.string)
+  result = (Path(res.head), Path(res.tail))
+
+func splitFile*(path: Path): tuple[dir, name: Path, ext: string] {.inline.} =
+  ## Splits a filename into `(dir, name, extension)` tuple.
+  ##
+  ## `dir` does not end in DirSep unless it's `/`.
+  ## `extension` includes the leading dot.
+  ##
+  ## If `path` has no extension, `ext` is the empty string.
+  ## If `path` has no directory component, `dir` is the empty string.
+  ## If `path` has no filename component, `name` and `ext` are empty strings.
+  ##
+  ## See also:
+  ## * `extractFilename proc`_
+  ## * `lastPathPart proc`_
+  ## * `changeFileExt proc`_
+  ## * `addFileExt proc`_
+  let res = splitFile(path.string)
+  result = (Path(res.dir), Path(res.name), res.ext)
+
+func isAbsolute*(path: Path): bool {.inline, raises: [].} =
+  ## Checks whether a given `path` is absolute.
+  ##
+  ## On Windows, network paths are considered absolute too.
+  result = isAbsolute(path.string)
+
+proc relativePath*(path, base: Path, sep = DirSep): Path {.inline.} =
+  ## Converts `path` to a path relative to `base`.
+  ##
+  ## The `sep` (default: DirSep) is used for the path normalizations,
+  ## this can be useful to ensure the relative path only contains `'/'`
+  ## so that it can be used for URL constructions.
+  ##
+  ## On Windows, if a root of `path` and a root of `base` are different,
+  ## returns `path` as is because it is impossible to make a relative path.
+  ## That means an absolute path can be returned.
+  ##
+  ## See also:
+  ## * `splitPath proc`_
+  ## * `parentDir proc`_
+  ## * `tailDir proc`_
+  result = Path(relativePath(path.string, base.string, sep))
+
+proc isRelativeTo*(path: Path, base: Path): bool {.inline.} =
+  ## Returns true if `path` is relative to `base`.
+  result = isRelativeTo(path.string, base.string)
+
+
+func parentDir*(path: Path): Path {.inline.} =
+  ## Returns the parent directory of `path`.
+  ##
+  ## This is similar to ``splitPath(path).head`` when ``path`` doesn't end
+  ## in a dir separator, but also takes care of path normalizations.
+  ## The remainder can be obtained with `lastPathPart(path) proc`_.
+  ##
+  ## See also:
+  ## * `relativePath proc`_
+  ## * `splitPath proc`_
+  ## * `tailDir proc`_
+  ## * `parentDirs iterator`_
+  result = Path(parentDir(path.string))
+
+func tailDir*(path: Path): Path {.inline.} =
+  ## Returns the tail part of `path`.
+  ##
+  ## See also:
+  ## * `relativePath proc`_
+  ## * `splitPath proc`_
+  ## * `parentDir proc`_
+  result = Path(tailDir(path.string))
+
+func isRootDir*(path: Path): bool {.inline.} =
+  ## Checks whether a given `path` is a root directory.
+  result = isRootDir(path.string)
+
+iterator parentDirs*(path: Path, fromRoot=false, inclusive=true): Path =
+  ## Walks over all parent directories of a given `path`.
+  ##
+  ## If `fromRoot` is true (default: false), the traversal will start from
+  ## the file system root directory.
+  ## If `inclusive` is true (default), the original argument will be included
+  ## in the traversal.
+  ##
+  ## Relative paths won't be expanded by this iterator. Instead, it will traverse
+  ## only the directories appearing in the relative path.
+  ##
+  ## See also:
+  ## * `parentDir proc`_
+  ##
+  for p in parentDirs(path.string, fromRoot, inclusive):
+    yield Path(p)
+
+func `/../`*(head, tail: Path): Path {.inline.} =
+  ## The same as ``parentDir(head) / tail``, unless there is no parent
+  ## directory. Then ``head / tail`` is performed instead.
+  ##
+  ## See also:
+  ## * `/ proc`_
+  ## * `parentDir proc`_
+  Path(`/../`(head.string, tail.string))
+
+func extractFilename*(path: Path): Path {.inline.} =
+  ## Extracts the filename of a given `path`.
+  ##
+  ## This is the same as ``name & ext`` from `splitFile(path) proc`_.
+  ##
+  ## See also:
+  ## * `splitFile proc`_
+  ## * `lastPathPart proc`_
+  ## * `changeFileExt proc`_
+  ## * `addFileExt proc`_
+  result = Path(extractFilename(path.string))
+
+func lastPathPart*(path: Path): Path {.inline.} =
+  ## Like `extractFilename proc`_, but ignores
+  ## trailing dir separator; aka: `baseName`:idx: in some other languages.
+  ##
+  ## See also:
+  ## * `splitFile proc`_
+  ## * `extractFilename proc`_
+  ## * `changeFileExt proc`_
+  ## * `addFileExt proc`_
+  result = Path(lastPathPart(path.string))
+
+func changeFileExt*(filename: Path, ext: string): Path {.inline.} =
+  ## Changes the file extension to `ext`.
+  ##
+  ## If the `filename` has no extension, `ext` will be added.
+  ## If `ext` == "" then any extension is removed.
+  ##
+  ## `Ext` should be given without the leading `'.'`, because some
+  ## filesystems may use a different character. (Although I know
+  ## of none such beast.)
+  ##
+  ## See also:
+  ## * `splitFile proc`_
+  ## * `extractFilename proc`_
+  ## * `lastPathPart proc`_
+  ## * `addFileExt proc`_
+  result = Path(changeFileExt(filename.string, ext))
+
+func addFileExt*(filename: Path, ext: string): Path {.inline.} =
+  ## Adds the file extension `ext` to `filename`, unless
+  ## `filename` already has an extension.
+  ##
+  ## `Ext` should be given without the leading `'.'`, because some
+  ## filesystems may use a different character.
+  ## (Although I know of none such beast.)
+  ##
+  ## See also:
+  ## * `splitFile proc`_
+  ## * `extractFilename proc`_
+  ## * `lastPathPart proc`_
+  ## * `changeFileExt proc`_
+  result = Path(addFileExt(filename.string, ext))
+
+func unixToNativePath*(path: Path, drive=Path("")): Path {.inline.} =
+  ## Converts an UNIX-like path to a native one.
+  ##
+  ## On an UNIX system this does nothing. Else it converts
+  ## `'/'`, `'.'`, `'..'` to the appropriate things.
+  ##
+  ## On systems with a concept of "drives", `drive` is used to determine
+  ## which drive label to use during absolute path conversion.
+  ## `drive` defaults to the drive of the current working directory, and is
+  ## ignored on systems that do not have a concept of "drives".
+  result = Path(unixToNativePath(path.string, drive.string))
+
+proc getCurrentDir*(): Path {.inline, tags: [].} =
+  ## Returns the `current working directory`:idx: i.e. where the built
+  ## binary is run.
+  ##
+  ## So the path returned by this proc is determined at run time.
+  ##
+  ## See also:
+  ## * `getHomeDir proc <appdirs.html#getHomeDir>`_
+  ## * `getConfigDir proc <appdirs.html#getConfigDir>`_
+  ## * `getTempDir proc <appdirs.html#getTempDir>`_
+  ## * `setCurrentDir proc <dirs.html#setCurrentDir>`_
+  ## * `currentSourcePath template <system.html#currentSourcePath.t>`_
+  ## * `getProjectPath proc <macros.html#getProjectPath>`_
+  result = Path(ospaths2.getCurrentDir())
+
+proc normalizeExe*(file: var Path) {.borrow.}
+
+proc normalizePath*(path: var Path) {.borrow.}
+
+proc normalizePathEnd*(path: var Path, trailingSep = false) {.borrow.}
+
+proc absolutePath*(path: Path, root = getCurrentDir()): Path =
+  ## Returns the absolute path of `path`, rooted at `root` (which must be absolute;
+  ## default: current directory).
+  ## If `path` is absolute, return it, ignoring `root`.
+  ##
+  ## See also:
+  ## * `normalizePath proc`_
+  result = Path(absolutePath(path.string, root.string))
+
+proc expandTildeImpl(path: string): string {.
+  tags: [ReadEnvEffect, ReadIOEffect].} =
+  if len(path) == 0 or path[0] != '~':
+    result = path
+  elif len(path) == 1:
+    result = getHomeDir()
+  elif (path[1] in {DirSep, AltSep}):
+    result = joinPath(getHomeDir(), path.substr(2))
+  else:
+    # TODO: handle `~bob` and `~bob/` which means home of bob
+    result = path
+
+proc expandTilde*(path: Path): Path {.inline,
+  tags: [ReadEnvEffect, ReadIOEffect].} =
+  ## Expands ``~`` or a path starting with ``~/`` to a full path, replacing
+  ## ``~`` with `getHomeDir() <appdirs.html#getHomeDir>`_ (otherwise returns ``path`` unmodified).
+  ##
+  ## Windows: this is still supported despite the Windows platform not having this
+  ## convention; also, both ``~/`` and ``~\`` are handled.
+  runnableExamples:
+    import std/appdirs
+    assert expandTilde(Path("~") / Path("appname.cfg")) == getHomeDir() / Path("appname.cfg")
+    assert expandTilde(Path("~/foo/bar")) == getHomeDir() / Path("foo/bar")
+    assert expandTilde(Path("/foo/bar")) == Path("/foo/bar")
+  result = Path(expandTildeImpl(path.string))
diff --git a/lib/std/private/dbutils.nim b/lib/std/private/dbutils.nim
deleted file mode 100644
index 0ae3b3702..000000000
--- a/lib/std/private/dbutils.nim
+++ /dev/null
@@ -1,15 +0,0 @@
-import db_common
-
-
-template dbFormatImpl*(formatstr: SqlQuery, dbQuote: proc (s: string): string, args: varargs[string]): string =
-  var res = ""
-  var a = 0
-  for c in items(string(formatstr)):
-    if c == '?':
-      if a == args.len:
-        dbError("""The number of "?" given exceeds the number of parameters present in the query.""")
-      add(res, dbQuote(args[a]))
-      inc(a)
-    else:
-      add(res, c)
-  res
diff --git a/lib/std/private/digitsutils.nim b/lib/std/private/digitsutils.nim
index 588bcaec0..f2d0d25cb 100644
--- a/lib/std/private/digitsutils.nim
+++ b/lib/std/private/digitsutils.nim
@@ -19,7 +19,7 @@ const
 
 # Inspired by https://engineering.fb.com/2013/03/15/developer-tools/three-optimization-tips-for-c
 # Generates:
-# .. code-block:: nim
+#   ```nim
 #   var res = ""
 #   for i in 0 .. 99:
 #     if i < 10:
@@ -27,14 +27,15 @@ const
 #     else:
 #       res.add $i
 #   doAssert res == digits100
+#   ```
 
 proc utoa2Digits*(buf: var openArray[char]; pos: int; digits: uint32) {.inline.} =
   buf[pos] = digits100[2 * digits]
   buf[pos+1] = digits100[2 * digits + 1]
   #copyMem(buf, unsafeAddr(digits100[2 * digits]), 2 * sizeof((char)))
 
-proc trailingZeros2Digits*(digits: uint32): int32 {.inline.} =
-  return trailingZeros100[digits]
+proc trailingZeros2Digits*(digits: uint32): int {.inline.} =
+  trailingZeros100[digits]
 
 when defined(js):
   proc numToString(a: SomeInteger): cstring {.importjs: "((#) + \"\")".}
@@ -63,14 +64,14 @@ func addIntImpl(result: var string, x: uint64) {.inline.} =
   while num >= nbatch:
     let originNum = num
     num = num div nbatch
-    let index = (originNum - num * nbatch) shl 1
+    let index = int16((originNum - num * nbatch) shl 1)
     tmp[next] = digits100[index + 1]
     tmp[next - 1] = digits100[index]
     dec(next, 2)
 
   # process last 1-2 digits
   if num < 10:
-    tmp[next] = chr(ord('0') + num)
+    tmp[next] = chr(ord('0') + num.uint8)
   else:
     let index = num * 2
     tmp[next] = digits100[index + 1]
@@ -101,9 +102,7 @@ proc addInt*(result: var string; x: int64) {.enforceNoRaises.} =
         num = cast[uint64](x)
       else:
         num = uint64(-x)
-      let base = result.len
-      setLen(result, base + 1)
-      result[base] = '-'
+      result.add '-'
     else:
       num = uint64(x)
     addInt(result, num)
diff --git a/lib/std/private/dragonbox.nim b/lib/std/private/dragonbox.nim
index 23adff385..85ffea84a 100644
--- a/lib/std/private/dragonbox.nim
+++ b/lib/std/private/dragonbox.nim
@@ -75,10 +75,10 @@ const
 const
   signMask*: BitsType = not (not BitsType(0) shr 1)
 
-proc constructDouble*(bits: BitsType): Double {.constructor.} =
+proc constructDouble*(bits: BitsType): Double  =
   result.bits = bits
 
-proc constructDouble*(value: ValueType): Double {.constructor.} =
+proc constructDouble*(value: ValueType): Double  =
   result.bits = cast[typeof(result.bits)](value)
 
 proc physicalSignificand*(this: Double): BitsType {.noSideEffect.} =
@@ -1052,7 +1052,7 @@ when false:
   proc memset(x: cstring; ch: char; L: int) {.importc, nodecl.}
   proc memmove(a, b: cstring; L: int) {.importc, nodecl.}
 
-proc utoa8DigitsSkipTrailingZeros*(buf: var openArray[char]; pos: int; digits: uint32): int32 {.inline.} =
+proc utoa8DigitsSkipTrailingZeros*(buf: var openArray[char]; pos: int; digits: uint32): int {.inline.} =
   dragonbox_Assert(digits >= 1)
   dragonbox_Assert(digits <= 99999999'u32)
   let q: uint32 = digits div 10000
@@ -1070,12 +1070,12 @@ proc utoa8DigitsSkipTrailingZeros*(buf: var openArray[char]; pos: int; digits: u
     utoa2Digits(buf, pos + 6, rL)
     return trailingZeros2Digits(if rL == 0: rH else: rL) + (if rL == 0: 2 else: 0)
 
-proc printDecimalDigitsBackwards*(buf: var openArray[char]; pos: int; output64: uint64): int32 {.inline.} =
+proc printDecimalDigitsBackwards*(buf: var openArray[char]; pos: int; output64: uint64): int {.inline.} =
   var pos = pos
   var output64 = output64
-  var tz: int32 = 0
+  var tz = 0
   ##  number of trailing zeros removed.
-  var nd: int32 = 0
+  var nd = 0
   ##  number of decimal digits processed.
   ##  At most 17 digits remaining
   if output64 >= 100000000'u64:
@@ -1146,7 +1146,7 @@ proc printDecimalDigitsBackwards*(buf: var openArray[char]; pos: int; output64:
     buf[pos] = chr(ord('0') + q)
   return tz
 
-proc decimalLength*(v: uint64): int32 {.inline.} =
+proc decimalLength*(v: uint64): int {.inline.} =
   dragonbox_Assert(v >= 1)
   dragonbox_Assert(v <= 99999999999999999'u64)
   if cast[uint32](v shr 32) != 0:
@@ -1166,48 +1166,48 @@ proc decimalLength*(v: uint64): int32 {.inline.} =
       return 11
     return 10
   let v32: uint32 = cast[uint32](v)
-  if v32 >= 1000000000'u:
+  if v32 >= 1000000000'u32:
     return 10
-  if v32 >= 100000000'u:
+  if v32 >= 100000000'u32:
     return 9
-  if v32 >= 10000000'u:
+  if v32 >= 10000000'u32:
     return 8
-  if v32 >= 1000000'u:
+  if v32 >= 1000000'u32:
     return 7
-  if v32 >= 100000'u:
+  if v32 >= 100000'u32:
     return 6
-  if v32 >= 10000'u:
+  if v32 >= 10000'u32:
     return 5
-  if v32 >= 1000'u:
+  if v32 >= 1000'u32:
     return 4
-  if v32 >= 100'u:
+  if v32 >= 100'u32:
     return 3
-  if v32 >= 10'u:
+  if v32 >= 10'u32:
     return 2
   return 1
 
-proc formatDigits*(buffer: var openArray[char]; pos: int; digits: uint64; decimalExponent: int32;
+proc formatDigits*[T: Ordinal](buffer: var openArray[char]; pos: T; digits: uint64; decimalExponent: int;
                   forceTrailingDotZero = false): int {.inline.} =
   const
-    minFixedDecimalPoint: int32 = -6
+    minFixedDecimalPoint = -6
   const
-    maxFixedDecimalPoint: int32 = 17
-  var pos = pos
+    maxFixedDecimalPoint = 17
+  var pos:int = pos.int
   assert(minFixedDecimalPoint <= -1, "internal error")
   assert(maxFixedDecimalPoint >= 17, "internal error")
   dragonbox_Assert(digits >= 1)
   dragonbox_Assert(digits <= 99999999999999999'u64)
   dragonbox_Assert(decimalExponent >= -999)
   dragonbox_Assert(decimalExponent <= 999)
-  var numDigits: int32 = decimalLength(digits)
-  let decimalPoint: int32 = numDigits + decimalExponent
+  var numDigits = decimalLength(digits)
+  let decimalPoint = numDigits + decimalExponent
   let useFixed: bool = minFixedDecimalPoint <= decimalPoint and
       decimalPoint <= maxFixedDecimalPoint
   ## Prepare the buffer.
   for i in 0..<32: buffer[pos+i] = '0'
   assert(minFixedDecimalPoint >= -30, "internal error")
   assert(maxFixedDecimalPoint <= 32, "internal error")
-  var decimalDigitsPosition: int32
+  var decimalDigitsPosition: int
   if useFixed:
     if decimalPoint <= 0:
       ##  0.[000]digits
@@ -1220,7 +1220,7 @@ proc formatDigits*(buffer: var openArray[char]; pos: int; digits: uint64; decima
     ##  dE+123 or d.igitsE+123
     decimalDigitsPosition = 1
   var digitsEnd = pos + int(decimalDigitsPosition + numDigits)
-  let tz: int32 = printDecimalDigitsBackwards(buffer, digitsEnd, digits)
+  let tz = printDecimalDigitsBackwards(buffer, digitsEnd, digits)
   dec(digitsEnd, tz)
   dec(numDigits, tz)
   ##   decimal_exponent += tz; // => decimal_point unchanged.
@@ -1258,7 +1258,7 @@ proc formatDigits*(buffer: var openArray[char]; pos: int; digits: uint64; decima
       ##  d.igitsE+123
       buffer[pos+1] = '.'
       pos = digitsEnd
-    let scientificExponent: int32 = decimalPoint - 1
+    let scientificExponent: int = decimalPoint - 1
     ##       SF_ASSERT(scientific_exponent != 0);
     buffer[pos] = 'e'
     buffer[pos+1] = if scientificExponent < 0: '-' else: '+'
@@ -1291,7 +1291,7 @@ proc toChars*(buffer: var openArray[char]; v: float; forceTrailingDotZero = fals
     if exponent != 0 or significand != 0:
       ##  != 0
       let dec = toDecimal64(significand, exponent)
-      return formatDigits(buffer, pos, dec.significand, dec.exponent,
+      return formatDigits(buffer, pos, dec.significand, dec.exponent.int,
                          forceTrailingDotZero)
     else:
       buffer[pos] = '0'
diff --git a/lib/std/private/gitutils.nim b/lib/std/private/gitutils.nim
index 5bcd9e377..6dc9c8f3b 100644
--- a/lib/std/private/gitutils.nim
+++ b/lib/std/private/gitutils.nim
@@ -4,7 +4,10 @@ internal API for now, API subject to change
 
 # xxx move other git utilities here; candidate for stdlib.
 
-import std/[os, osproc, strutils, tempfiles]
+import std/[os, paths, osproc, strutils, tempfiles]
+
+when defined(nimPreviewSlimSystem):
+  import std/[assertions, syncio]
 
 const commitHead* = "HEAD"
 
@@ -29,15 +32,8 @@ template retryCall*(maxRetry = 3, backoffDuration = 1.0, call: untyped): bool =
   result
 
 proc isGitRepo*(dir: string): bool =
-  ## This command is used to get the relative path to the root of the repository.
-  ## Using this, we can verify whether a folder is a git repository by checking
-  ## whether the command success and if the output is empty.
-  let (output, status) = execCmdEx("git rev-parse --show-cdup", workingDir = dir)
-  # On Windows there will be a trailing newline on success, remove it.
-  # The value of a successful call typically won't have a whitespace (it's
-  # usually a series of ../), so we know that it's safe to unconditionally
-  # remove trailing whitespaces from the result.
-  result = status == 0 and output.strip() == ""
+  ## Avoid calling git since it depends on /bin/sh existing and fails in Nix.
+  return fileExists(dir/".git/HEAD")
 
 proc diffFiles*(path1, path2: string): tuple[output: string, same: bool] =
   ## Returns a human readable diff of files `path1`, `path2`, the exact form of
diff --git a/lib/std/private/globs.nim b/lib/std/private/globs.nim
index 28a810372..a6d088558 100644
--- a/lib/std/private/globs.nim
+++ b/lib/std/private/globs.nim
@@ -4,12 +4,12 @@ this can eventually be moved to std/os and `walkDirRec` can be implemented in te
 to avoid duplication
 ]##
 
-import os
+import std/os
 when defined(windows):
-  from strutils import replace
+  from std/strutils import replace
 
 when defined(nimPreviewSlimSystem):
-  import std/assertions
+  import std/[assertions, objectdollar]
 
 
 when defined(nimHasEffectsOf):
@@ -60,11 +60,11 @@ proc nativeToUnixPath*(path: string): string =
       result[0] = '/'
       result[1] = path[0]
       if path.len > 2 and path[2] != '\\':
-        doAssert false, "paths like `C:foo` are currently unsupported, path: " & path
+        raiseAssert "paths like `C:foo` are currently unsupported, path: " & path
   when DirSep == '\\':
     result = replace(result, '\\', '/')
 
 when isMainModule:
-  import sugar
+  import std/sugar
   for a in walkDirRecFilter(".", follow = a=>a.path.lastPathPart notin ["nimcache", ".git", "csources_v1", "csources", "bin"]):
     echo a
diff --git a/lib/std/private/jsutils.nim b/lib/std/private/jsutils.nim
index 836b3512a..5f79eab27 100644
--- a/lib/std/private/jsutils.nim
+++ b/lib/std/private/jsutils.nim
@@ -37,13 +37,13 @@ when defined(js):
       let a = array[2, float64].default
       assert jsConstructorName(a) == "Float64Array"
       assert jsConstructorName(a.toJs) == "Float64Array"
-    asm """`result` = `a`.constructor.name"""
+    {.emit: """`result` = `a`.constructor.name;""".}
 
   proc hasJsBigInt*(): bool =
-    asm """`result` = typeof BigInt != 'undefined'"""
+    {.emit: """`result` = typeof BigInt != 'undefined';""".}
 
   proc hasBigUint64Array*(): bool =
-    asm """`result` = typeof BigUint64Array != 'undefined'"""
+    {.emit: """`result` = typeof BigUint64Array != 'undefined';""".}
 
   proc getProtoName*[T](a: T): cstring {.importjs: "Object.prototype.toString.call(#)".} =
     runnableExamples:
@@ -79,5 +79,18 @@ when defined(js):
       assert not "123".toJs.isSafeInteger
       assert 123.isSafeInteger
       assert 123.toJs.isSafeInteger
-      assert 9007199254740991.toJs.isSafeInteger
-      assert not 9007199254740992.toJs.isSafeInteger
+      when false:
+        assert 9007199254740991.toJs.isSafeInteger
+        assert not 9007199254740992.toJs.isSafeInteger
+
+template whenJsNoBigInt64*(no64, yes64): untyped =
+  when defined(js):
+    when compiles(compileOption("jsbigint64")):
+      when compileOption("jsbigint64"):
+        yes64
+      else:
+        no64
+    else:
+      no64
+  else:
+    no64
diff --git a/lib/std/private/miscdollars.nim b/lib/std/private/miscdollars.nim
index 47b788ee9..06fda6fa1 100644
--- a/lib/std/private/miscdollars.nim
+++ b/lib/std/private/miscdollars.nim
@@ -13,21 +13,7 @@ template toLocation*(result: var string, file: string | cstring, line: int, col:
       addInt(result, col)
     result.add ")"
 
-when defined(nimHasIsNamedTuple):
-  proc isNamedTuple(T: typedesc): bool {.magic: "TypeTrait".}
-else:
-  # for bootstrap; remove after release 1.2
-  proc isNamedTuple(T: typedesc): bool =
-    # Taken from typetraits.
-    when T isnot tuple: result = false
-    else:
-      var t: T
-      for name, _ in t.fieldPairs:
-        when name == "Field0":
-          return compiles(t.Field0)
-        else:
-          return true
-      return false
+proc isNamedTuple(T: typedesc): bool {.magic: "TypeTrait".}
 
 template tupleObjectDollar*[T: tuple | object](result: var string, x: T) =
   result = "("
diff --git a/lib/std/private/osappdirs.nim b/lib/std/private/osappdirs.nim
new file mode 100644
index 000000000..07a6809bb
--- /dev/null
+++ b/lib/std/private/osappdirs.nim
@@ -0,0 +1,176 @@
+## .. importdoc:: paths.nim, dirs.nim
+
+include system/inclrtl
+import std/envvars
+import std/private/ospaths2
+
+proc getHomeDir*(): string {.rtl, extern: "nos$1",
+  tags: [ReadEnvEffect, ReadIOEffect].} =
+  ## Returns the home directory of the current user.
+  ##
+  ## This proc is wrapped by the `expandTilde proc`_
+  ## for the convenience of processing paths coming from user configuration files.
+  ##
+  ## See also:
+  ## * `getDataDir proc`_
+  ## * `getConfigDir proc`_
+  ## * `getTempDir proc`_
+  ## * `expandTilde proc`_
+  ## * `getCurrentDir proc`_
+  ## * `setCurrentDir proc`_
+  runnableExamples:
+    import std/os
+    assert getHomeDir() == expandTilde("~")
+
+  when defined(windows): return getEnv("USERPROFILE") & "\\"
+  else: return getEnv("HOME") & "/"
+
+proc getDataDir*(): string {.rtl, extern: "nos$1"
+  tags: [ReadEnvEffect, ReadIOEffect].} =
+  ## Returns the data directory of the current user for applications.
+  ## 
+  ## On non-Windows OSs, this proc conforms to the XDG Base Directory
+  ## spec. Thus, this proc returns the value of the `XDG_DATA_HOME` environment
+  ## variable if it is set, otherwise it returns the default configuration
+  ## directory ("~/.local/share" or "~/Library/Application Support" on macOS).
+  ## 
+  ## See also:
+  ## * `getHomeDir proc`_
+  ## * `getConfigDir proc`_
+  ## * `getTempDir proc`_
+  ## * `expandTilde proc`_
+  ## * `getCurrentDir proc`_
+  ## * `setCurrentDir proc`_
+  when defined(windows):
+    result = getEnv("APPDATA")
+  elif defined(macosx):
+    result = getEnv("XDG_DATA_HOME", getEnv("HOME") / "Library" / "Application Support")
+  else:
+    result = getEnv("XDG_DATA_HOME", getEnv("HOME") / ".local" / "share")
+  result.normalizePathEnd(trailingSep = true)
+
+proc getConfigDir*(): string {.rtl, extern: "nos$1",
+  tags: [ReadEnvEffect, ReadIOEffect].} =
+  ## Returns the config directory of the current user for applications.
+  ##
+  ## On non-Windows OSs, this proc conforms to the XDG Base Directory
+  ## spec. Thus, this proc returns the value of the `XDG_CONFIG_HOME` environment
+  ## variable if it is set, otherwise it returns the default configuration
+  ## directory ("~/.config/").
+  ##
+  ## An OS-dependent trailing slash is always present at the end of the
+  ## returned string: `\\` on Windows and `/` on all other OSs.
+  ##
+  ## See also:
+  ## * `getHomeDir proc`_
+  ## * `getDataDir proc`_
+  ## * `getTempDir proc`_
+  ## * `expandTilde proc`_
+  ## * `getCurrentDir proc`_
+  ## * `setCurrentDir proc`_
+  when defined(windows):
+    result = getEnv("APPDATA")
+  else:
+    result = getEnv("XDG_CONFIG_HOME", getEnv("HOME") / ".config")
+  result.normalizePathEnd(trailingSep = true)
+
+proc getCacheDir*(): string =
+  ## Returns the cache directory of the current user for applications.
+  ##
+  ## This makes use of the following environment variables:
+  ##
+  ## * On Windows: `getEnv("LOCALAPPDATA")`
+  ##
+  ## * On macOS: `getEnv("XDG_CACHE_HOME", getEnv("HOME") / "Library/Caches")`
+  ##
+  ## * On other platforms: `getEnv("XDG_CACHE_HOME", getEnv("HOME") / ".cache")`
+  ##
+  ## **See also:**
+  ## * `getHomeDir proc`_
+  ## * `getTempDir proc`_
+  ## * `getConfigDir proc`_
+  ## * `getDataDir proc`_
+  # follows https://crates.io/crates/platform-dirs
+  when defined(windows):
+    result = getEnv("LOCALAPPDATA")
+  elif defined(osx):
+    result = getEnv("XDG_CACHE_HOME", getEnv("HOME") / "Library/Caches")
+  else:
+    result = getEnv("XDG_CACHE_HOME", getEnv("HOME") / ".cache")
+  result.normalizePathEnd(false)
+
+proc getCacheDir*(app: string): string =
+  ## Returns the cache directory for an application `app`.
+  ##
+  ## * On Windows, this uses: `getCacheDir() / app / "cache"`
+  ## * On other platforms, this uses: `getCacheDir() / app`
+  when defined(windows):
+    getCacheDir() / app / "cache"
+  else:
+    getCacheDir() / app
+
+
+when defined(windows):
+  type DWORD = uint32
+
+  when defined(nimPreviewSlimSystem):
+    import std/widestrs
+
+  proc getTempPath(
+    nBufferLength: DWORD, lpBuffer: WideCString
+  ): DWORD {.stdcall, dynlib: "kernel32.dll", importc: "GetTempPathW".} =
+    ## Retrieves the path of the directory designated for temporary files.
+
+template getEnvImpl(result: var string, tempDirList: openArray[string]) =
+  for dir in tempDirList:
+    if existsEnv(dir):
+      result = getEnv(dir)
+      break
+
+template getTempDirImpl(result: var string) =
+  when defined(windows):
+    getEnvImpl(result, ["TMP", "TEMP", "USERPROFILE"])
+  else:
+    getEnvImpl(result, ["TMPDIR", "TEMP", "TMP", "TEMPDIR"])
+
+proc getTempDir*(): string {.rtl, extern: "nos$1",
+  tags: [ReadEnvEffect, ReadIOEffect].} =
+  ## Returns the temporary directory of the current user for applications to
+  ## save temporary files in.
+  ##
+  ## On Windows, it calls [GetTempPath](https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-gettemppathw).
+  ## On Posix based platforms, it will check `TMPDIR`, `TEMP`, `TMP` and `TEMPDIR` environment variables in order.
+  ## On all platforms, `/tmp` will be returned if the procs fails.
+  ##
+  ## You can override this implementation
+  ## by adding `-d:tempDir=mytempname` to your compiler invocation.
+  ##
+  ## **Note:** This proc does not check whether the returned path exists.
+  ##
+  ## See also:
+  ## * `getHomeDir proc`_
+  ## * `getConfigDir proc`_
+  ## * `expandTilde proc`_
+  ## * `getCurrentDir proc`_
+  ## * `setCurrentDir proc`_
+  const tempDirDefault = "/tmp"
+  when defined(tempDir):
+    const tempDir {.strdefine.}: string = tempDirDefault
+    result = tempDir
+  else:
+    when nimvm:
+      getTempDirImpl(result)
+    else:
+      when defined(windows):
+        let size = getTempPath(0, nil)
+        # If the function fails, the return value is zero.
+        if size > 0:
+          let buffer = newWideCString(size.int)
+          if getTempPath(size, buffer) > 0:
+            result = $buffer
+      elif defined(android): result = "/data/local/tmp"
+      else:
+        getTempDirImpl(result)
+    if result.len == 0:
+      result = tempDirDefault
+  normalizePathEnd(result, trailingSep=true)
diff --git a/lib/std/private/oscommon.nim b/lib/std/private/oscommon.nim
new file mode 100644
index 000000000..c49d52ef2
--- /dev/null
+++ b/lib/std/private/oscommon.nim
@@ -0,0 +1,186 @@
+include system/inclrtl
+
+import std/[oserrors]
+
+when defined(nimPreviewSlimSystem):
+  import std/[syncio, assertions, widestrs]
+
+## .. importdoc:: osdirs.nim, os.nim
+
+const weirdTarget* = defined(nimscript) or defined(js)
+
+
+type
+  ReadDirEffect* = object of ReadIOEffect   ## Effect that denotes a read
+                                            ## operation from the directory
+                                            ## structure.
+  WriteDirEffect* = object of WriteIOEffect ## Effect that denotes a write
+                                            ## operation to
+                                            ## the directory structure.
+
+
+when weirdTarget:
+  discard
+elif defined(windows):
+  import std/[winlean, times]
+elif defined(posix):
+  import std/posix
+  proc c_rename(oldname, newname: cstring): cint {.
+    importc: "rename", header: "<stdio.h>".}
+else:
+  {.error: "OS module not ported to your operating system!".}
+
+
+when weirdTarget:
+  {.pragma: noWeirdTarget, error: "this proc is not available on the NimScript/js target".}
+else:
+  {.pragma: noWeirdTarget.}
+
+
+when defined(nimscript):
+  # for procs already defined in scriptconfig.nim
+  template noNimJs(body): untyped = discard
+elif defined(js):
+  {.pragma: noNimJs, error: "this proc is not available on the js target".}
+else:
+  {.pragma: noNimJs.}
+
+
+when defined(windows) and not weirdTarget:
+  template wrapUnary*(varname, winApiProc, arg: untyped) =
+    var varname = winApiProc(newWideCString(arg))
+
+  template wrapBinary*(varname, winApiProc, arg, arg2: untyped) =
+    var varname = winApiProc(newWideCString(arg), arg2)
+  proc findFirstFile*(a: string, b: var WIN32_FIND_DATA): Handle =
+    result = findFirstFileW(newWideCString(a), b)
+  template findNextFile*(a, b: untyped): untyped = findNextFileW(a, b)
+
+  template getFilename*(f: untyped): untyped =
+    $cast[WideCString](addr(f.cFileName[0]))
+
+  proc skipFindData*(f: WIN32_FIND_DATA): bool {.inline.} =
+    # Note - takes advantage of null delimiter in the cstring
+    const dot = ord('.')
+    result = f.cFileName[0].int == dot and (f.cFileName[1].int == 0 or
+             f.cFileName[1].int == dot and f.cFileName[2].int == 0)
+
+
+type
+  PathComponent* = enum   ## Enumeration specifying a path component.
+    ##
+    ## See also:
+    ## * `walkDirRec iterator`_
+    ## * `FileInfo object`_
+    pcFile,               ## path refers to a file
+    pcLinkToFile,         ## path refers to a symbolic link to a file
+    pcDir,                ## path refers to a directory
+    pcLinkToDir           ## path refers to a symbolic link to a directory
+
+
+when defined(posix) and not weirdTarget:
+  proc getSymlinkFileKind*(path: string):
+      tuple[pc: PathComponent, isSpecial: bool] =
+    # Helper function.
+    var s: Stat
+    assert(path != "")
+    result = (pcLinkToFile, false)
+    if stat(path, s) == 0'i32:
+      if S_ISDIR(s.st_mode):
+        result = (pcLinkToDir, false)
+      elif not S_ISREG(s.st_mode):
+        result = (pcLinkToFile, true)
+
+proc tryMoveFSObject*(source, dest: string, isDir: bool): bool {.noWeirdTarget.} =
+  ## Moves a file (or directory if `isDir` is true) from `source` to `dest`.
+  ##
+  ## Returns false in case of `EXDEV` error or `AccessDeniedError` on Windows (if `isDir` is true).
+  ## In case of other errors `OSError` is raised.
+  ## Returns true in case of success.
+  when defined(windows):
+    let s = newWideCString(source)
+    let d = newWideCString(dest)
+    result = moveFileExW(s, d, MOVEFILE_COPY_ALLOWED or MOVEFILE_REPLACE_EXISTING) != 0'i32
+  else:
+    result = c_rename(source, dest) == 0'i32
+
+  if not result:
+    let err = osLastError()
+    let isAccessDeniedError =
+      when defined(windows):
+        const AccessDeniedError = OSErrorCode(5)
+        isDir and err == AccessDeniedError
+      else:
+        err == EXDEV.OSErrorCode
+    if not isAccessDeniedError:
+      raiseOSError(err, $(source, dest))
+
+when not defined(windows):
+  const maxSymlinkLen* = 1024
+
+proc fileExists*(filename: string): bool {.rtl, extern: "nos$1",
+                                          tags: [ReadDirEffect], noNimJs, sideEffect.} =
+  ## Returns true if `filename` exists and is a regular file or symlink.
+  ##
+  ## Directories, device files, named pipes and sockets return false.
+  ##
+  ## See also:
+  ## * `dirExists proc`_
+  ## * `symlinkExists proc`_
+  when defined(windows):
+    wrapUnary(a, getFileAttributesW, filename)
+    if a != -1'i32:
+      result = (a and FILE_ATTRIBUTE_DIRECTORY) == 0'i32
+  else:
+    var res: Stat
+    return stat(filename, res) >= 0'i32 and S_ISREG(res.st_mode)
+
+
+proc dirExists*(dir: string): bool {.rtl, extern: "nos$1", tags: [ReadDirEffect],
+                                     noNimJs, sideEffect.} =
+  ## Returns true if the directory `dir` exists. If `dir` is a file, false
+  ## is returned. Follows symlinks.
+  ##
+  ## See also:
+  ## * `fileExists proc`_
+  ## * `symlinkExists proc`_
+  when defined(windows):
+    wrapUnary(a, getFileAttributesW, dir)
+    if a != -1'i32:
+      result = (a and FILE_ATTRIBUTE_DIRECTORY) != 0'i32
+  else:
+    var res: Stat
+    result = stat(dir, res) >= 0'i32 and S_ISDIR(res.st_mode)
+
+
+proc symlinkExists*(link: string): bool {.rtl, extern: "nos$1",
+                                          tags: [ReadDirEffect],
+                                          noWeirdTarget, sideEffect.} =
+  ## Returns true if the symlink `link` exists. Will return true
+  ## regardless of whether the link points to a directory or file.
+  ##
+  ## See also:
+  ## * `fileExists proc`_
+  ## * `dirExists proc`_
+  when defined(windows):
+    wrapUnary(a, getFileAttributesW, link)
+    if a != -1'i32:
+      # xxx see: bug #16784 (bug9); checking `IO_REPARSE_TAG_SYMLINK`
+      # may also be needed.
+      result = (a and FILE_ATTRIBUTE_REPARSE_POINT) != 0'i32
+  else:
+    var res: Stat
+    result = lstat(link, res) >= 0'i32 and S_ISLNK(res.st_mode)
+
+when defined(windows) and not weirdTarget:
+  proc openHandle*(path: string, followSymlink=true, writeAccess=false): Handle =
+    var flags = FILE_FLAG_BACKUP_SEMANTICS or FILE_ATTRIBUTE_NORMAL
+    if not followSymlink:
+      flags = flags or FILE_FLAG_OPEN_REPARSE_POINT
+    let access = if writeAccess: GENERIC_WRITE else: 0'i32
+
+    result = createFileW(
+      newWideCString(path), access,
+      FILE_SHARE_DELETE or FILE_SHARE_READ or FILE_SHARE_WRITE,
+      nil, OPEN_EXISTING, flags, 0
+      )
diff --git a/lib/std/private/osdirs.nim b/lib/std/private/osdirs.nim
new file mode 100644
index 000000000..a44cad7d9
--- /dev/null
+++ b/lib/std/private/osdirs.nim
@@ -0,0 +1,570 @@
+## .. importdoc:: osfiles.nim, appdirs.nim, paths.nim
+
+include system/inclrtl
+import std/oserrors
+
+
+import ospaths2, osfiles
+import oscommon
+export dirExists, PathComponent
+
+
+when defined(nimPreviewSlimSystem):
+  import std/[syncio, assertions, widestrs]
+
+
+when weirdTarget:
+  discard
+elif defined(windows):
+  import std/[winlean, times]
+elif defined(posix):
+  import std/[posix, times]
+
+else:
+  {.error: "OS module not ported to your operating system!".}
+
+
+when weirdTarget:
+  {.pragma: noWeirdTarget, error: "this proc is not available on the NimScript/js target".}
+else:
+  {.pragma: noWeirdTarget.}
+
+
+when defined(nimscript):
+  # for procs already defined in scriptconfig.nim
+  template noNimJs(body): untyped = discard
+elif defined(js):
+  {.pragma: noNimJs, error: "this proc is not available on the js target".}
+else:
+  {.pragma: noNimJs.}
+
+# Templates for filtering directories and files
+when defined(windows) and not weirdTarget:
+  template isDir(f: WIN32_FIND_DATA): bool =
+    (f.dwFileAttributes and FILE_ATTRIBUTE_DIRECTORY) != 0'i32
+  template isFile(f: WIN32_FIND_DATA): bool =
+    not isDir(f)
+else:
+  template isDir(f: string): bool {.dirty.} =
+    dirExists(f)
+  template isFile(f: string): bool {.dirty.} =
+    fileExists(f)
+
+template defaultWalkFilter(item): bool =
+  ## Walk filter used to return true on both
+  ## files and directories
+  true
+
+template walkCommon(pattern: string, filter) =
+  ## Common code for getting the files and directories with the
+  ## specified `pattern`
+  when defined(windows):
+    var
+      f: WIN32_FIND_DATA
+      res: int
+    res = findFirstFile(pattern, f)
+    if res != -1:
+      defer: findClose(res)
+      let dotPos = searchExtPos(pattern)
+      while true:
+        if not skipFindData(f) and filter(f):
+          # Windows bug/gotcha: 't*.nim' matches 'tfoo.nims' -.- so we check
+          # that the file extensions have the same length ...
+          let ff = getFilename(f)
+          let idx = ff.len - pattern.len + dotPos
+          if dotPos < 0 or idx >= ff.len or (idx >= 0 and ff[idx] == '.') or
+              (dotPos >= 0 and dotPos+1 < pattern.len and pattern[dotPos+1] == '*'):
+            yield splitFile(pattern).dir / extractFilename(ff)
+        if findNextFile(res, f) == 0'i32:
+          let errCode = getLastError()
+          if errCode == ERROR_NO_MORE_FILES: break
+          else: raiseOSError(errCode.OSErrorCode)
+  else: # here we use glob
+    var
+      f: Glob
+      res: int
+    f.gl_offs = 0
+    f.gl_pathc = 0
+    f.gl_pathv = nil
+    res = glob(pattern, 0, nil, addr(f))
+    defer: globfree(addr(f))
+    if res == 0:
+      for i in 0.. f.gl_pathc - 1:
+        assert(f.gl_pathv[i] != nil)
+        let path = $f.gl_pathv[i]
+        if filter(path):
+          yield path
+
+iterator walkPattern*(pattern: string): string {.tags: [ReadDirEffect], noWeirdTarget.} =
+  ## Iterate over all the files and directories that match the `pattern`.
+  ##
+  ## On POSIX this uses the `glob`:idx: call.
+  ## `pattern` is OS dependent, but at least the `"*.ext"`
+  ## notation is supported.
+  ##
+  ## See also:
+  ## * `walkFiles iterator`_
+  ## * `walkDirs iterator`_
+  ## * `walkDir iterator`_
+  ## * `walkDirRec iterator`_
+  runnableExamples:
+    import std/os
+    import std/sequtils
+    let paths = toSeq(walkPattern("lib/pure/*")) # works on Windows too
+    assert "lib/pure/concurrency".unixToNativePath in paths
+    assert "lib/pure/os.nim".unixToNativePath in paths
+  walkCommon(pattern, defaultWalkFilter)
+
+iterator walkFiles*(pattern: string): string {.tags: [ReadDirEffect], noWeirdTarget.} =
+  ## Iterate over all the files that match the `pattern`.
+  ##
+  ## On POSIX this uses the `glob`:idx: call.
+  ## `pattern` is OS dependent, but at least the `"*.ext"`
+  ## notation is supported.
+  ##
+  ## See also:
+  ## * `walkPattern iterator`_
+  ## * `walkDirs iterator`_
+  ## * `walkDir iterator`_
+  ## * `walkDirRec iterator`_
+  runnableExamples:
+    import std/os
+    import std/sequtils
+    assert "lib/pure/os.nim".unixToNativePath in toSeq(walkFiles("lib/pure/*.nim")) # works on Windows too
+  walkCommon(pattern, isFile)
+
+iterator walkDirs*(pattern: string): string {.tags: [ReadDirEffect], noWeirdTarget.} =
+  ## Iterate over all the directories that match the `pattern`.
+  ##
+  ## On POSIX this uses the `glob`:idx: call.
+  ## `pattern` is OS dependent, but at least the `"*.ext"`
+  ## notation is supported.
+  ##
+  ## See also:
+  ## * `walkPattern iterator`_
+  ## * `walkFiles iterator`_
+  ## * `walkDir iterator`_
+  ## * `walkDirRec iterator`_
+  runnableExamples:
+    import std/os
+    import std/sequtils
+    let paths = toSeq(walkDirs("lib/pure/*")) # works on Windows too
+    assert "lib/pure/concurrency".unixToNativePath in paths
+  walkCommon(pattern, isDir)
+
+proc staticWalkDir(dir: string; relative: bool): seq[
+                  tuple[kind: PathComponent, path: string]] =
+  discard
+
+iterator walkDir*(dir: string; relative = false, checkDir = false,
+                  skipSpecial = false):
+  tuple[kind: PathComponent, path: string] {.tags: [ReadDirEffect].} =
+  ## Walks over the directory `dir` and yields for each directory or file in
+  ## `dir`. The component type and full path for each item are returned.
+  ##
+  ## Walking is not recursive.
+  ## * If `relative` is true (default: false)
+  ##   the resulting path is shortened to be relative to ``dir``,
+  ##   otherwise the full path is returned.
+  ## * If `checkDir` is true, `OSError` is raised when `dir`
+  ##   doesn't exist.
+  ## * If `skipSpecial` is true, then (besides all directories) only *regular*
+  ##   files (**without** special "file" objects like FIFOs, device files,
+  ##   etc) will be yielded on Unix.
+  ##
+  ## **Example:**
+  ##
+  ## This directory structure:
+  ##
+  ##     dirA / dirB / fileB1.txt
+  ##          / dirC
+  ##          / fileA1.txt
+  ##          / fileA2.txt
+  ##
+  ## and this code:
+  runnableExamples("-r:off"):
+    import std/[strutils, sugar]
+    # note: order is not guaranteed
+    # this also works at compile time
+    assert collect(for k in walkDir("dirA"): k.path).join(" ") ==
+                          "dirA/dirB dirA/dirC dirA/fileA2.txt dirA/fileA1.txt"
+  ## See also:
+  ## * `walkPattern iterator`_
+  ## * `walkFiles iterator`_
+  ## * `walkDirs iterator`_
+  ## * `walkDirRec iterator`_
+
+  when nimvm:
+    for k, v in items(staticWalkDir(dir, relative)):
+      yield (k, v)
+  else:
+    when weirdTarget:
+      for k, v in items(staticWalkDir(dir, relative)):
+        yield (k, v)
+    elif defined(windows):
+      var f: WIN32_FIND_DATA
+      var h = findFirstFile(dir / "*", f)
+      if h == -1:
+        if checkDir:
+          raiseOSError(osLastError(), dir)
+      else:
+        defer: findClose(h)
+        while true:
+          var k = pcFile
+          if not skipFindData(f):
+            if (f.dwFileAttributes and FILE_ATTRIBUTE_DIRECTORY) != 0'i32:
+              k = pcDir
+            if (f.dwFileAttributes and FILE_ATTRIBUTE_REPARSE_POINT) != 0'i32:
+              k = succ(k)
+            let xx = if relative: extractFilename(getFilename(f))
+                     else: dir / extractFilename(getFilename(f))
+            yield (k, xx)
+          if findNextFile(h, f) == 0'i32:
+            let errCode = getLastError()
+            if errCode == ERROR_NO_MORE_FILES: break
+            else: raiseOSError(errCode.OSErrorCode)
+    else:
+      var d = opendir(dir)
+      if d == nil:
+        if checkDir:
+          raiseOSError(osLastError(), dir)
+      else:
+        defer: discard closedir(d)
+        while true:
+          var x = readdir(d)
+          if x == nil: break
+          var y = $cast[cstring](addr x.d_name)
+          if y != "." and y != "..":
+            var s: Stat
+            let path = dir / y
+            if not relative:
+              y = path
+            var k = pcFile
+
+            template resolveSymlink() =
+              var isSpecial: bool
+              (k, isSpecial) = getSymlinkFileKind(path)
+              if skipSpecial and isSpecial: continue
+
+            template kSetGeneric() =  # pure Posix component `k` resolution
+              if lstat(path.cstring, s) < 0'i32: continue  # don't yield
+              elif S_ISDIR(s.st_mode):
+                k = pcDir
+              elif S_ISLNK(s.st_mode):
+                resolveSymlink()
+              elif skipSpecial and not S_ISREG(s.st_mode): continue
+
+            when defined(linux) or defined(macosx) or
+                 defined(bsd) or defined(genode) or defined(nintendoswitch):
+              case x.d_type
+              of DT_DIR: k = pcDir
+              of DT_LNK:
+                resolveSymlink()
+              of DT_UNKNOWN:
+                kSetGeneric()
+              else: # DT_REG or special "files" like FIFOs
+                if skipSpecial and x.d_type != DT_REG: continue
+                else: discard # leave it as pcFile
+            else:  # assuming that field `d_type` is not present
+              kSetGeneric()
+
+            yield (k, y)
+
+iterator walkDirRec*(dir: string,
+                     yieldFilter = {pcFile}, followFilter = {pcDir},
+                     relative = false, checkDir = false, skipSpecial = false):
+                    string {.tags: [ReadDirEffect].} =
+  ## Recursively walks over the directory `dir` and yields for each file
+  ## or directory in `dir`.
+  ##
+  ## Options `relative`, `checkdir`, `skipSpecial` are explained in
+  ## [walkDir iterator] description.
+  ##
+  ## .. warning:: Modifying the directory structure while the iterator
+  ##   is traversing may result in undefined behavior!
+  ##
+  ## Walking is recursive. `followFilter` controls the behaviour of the iterator:
+  ##
+  ## =====================   =============================================
+  ## yieldFilter             meaning
+  ## =====================   =============================================
+  ## ``pcFile``              yield real files (default)
+  ## ``pcLinkToFile``        yield symbolic links to files
+  ## ``pcDir``               yield real directories
+  ## ``pcLinkToDir``         yield symbolic links to directories
+  ## =====================   =============================================
+  ##
+  ## =====================   =============================================
+  ## followFilter            meaning
+  ## =====================   =============================================
+  ## ``pcDir``               follow real directories (default)
+  ## ``pcLinkToDir``         follow symbolic links to directories
+  ## =====================   =============================================
+  ##
+  ##
+  ## See also:
+  ## * `walkPattern iterator`_
+  ## * `walkFiles iterator`_
+  ## * `walkDirs iterator`_
+  ## * `walkDir iterator`_
+
+  var stack = @[""]
+  var checkDir = checkDir
+  while stack.len > 0:
+    let d = stack.pop()
+    for k, p in walkDir(dir / d, relative = true, checkDir = checkDir,
+                        skipSpecial = skipSpecial):
+      let rel = d / p
+      if k in {pcDir, pcLinkToDir} and k in followFilter:
+        stack.add rel
+      if k in yieldFilter:
+        yield if relative: rel else: dir / rel
+    checkDir = false
+      # We only check top-level dir, otherwise if a subdir is invalid (eg. wrong
+      # permissions), it'll abort iteration and there would be no way to
+      # continue iteration.
+      # Future work can provide a way to customize this and do error reporting.
+
+
+proc rawRemoveDir(dir: string) {.noWeirdTarget.} =
+  when defined(windows):
+    wrapUnary(res, removeDirectoryW, dir)
+    let lastError = osLastError()
+    if res == 0'i32 and lastError.int32 != 3'i32 and
+        lastError.int32 != 18'i32 and lastError.int32 != 2'i32:
+      raiseOSError(lastError, dir)
+  else:
+    if rmdir(dir) != 0'i32 and errno != ENOENT: raiseOSError(osLastError(), dir)
+
+proc removeDir*(dir: string, checkDir = false) {.rtl, extern: "nos$1", tags: [
+  WriteDirEffect, ReadDirEffect], benign, noWeirdTarget.} =
+  ## Removes the directory `dir` including all subdirectories and files
+  ## in `dir` (recursively).
+  ##
+  ## If this fails, `OSError` is raised. This does not fail if the directory never
+  ## existed in the first place, unless `checkDir` = true.
+  ##
+  ## See also:
+  ## * `tryRemoveFile proc`_
+  ## * `removeFile proc`_
+  ## * `existsOrCreateDir proc`_
+  ## * `createDir proc`_
+  ## * `copyDir proc`_
+  ## * `copyDirWithPermissions proc`_
+  ## * `moveDir proc`_
+  for kind, path in walkDir(dir, checkDir = checkDir):
+    case kind
+    of pcFile, pcLinkToFile, pcLinkToDir: removeFile(path)
+    of pcDir: removeDir(path, true)
+      # for subdirectories there is no benefit in `checkDir = false`
+      # (unless perhaps for edge case of concurrent processes also deleting
+      # the same files)
+  rawRemoveDir(dir)
+
+proc rawCreateDir(dir: string): bool {.noWeirdTarget.} =
+  # Try to create one directory (not the whole path).
+  # returns `true` for success, `false` if the path has previously existed
+  #
+  # This is a thin wrapper over mkDir (or alternatives on other systems),
+  # so in case of a pre-existing path we don't check that it is a directory.
+  when defined(solaris):
+    let res = mkdir(dir, 0o777)
+    if res == 0'i32:
+      result = true
+    elif errno in {EEXIST, ENOSYS}:
+      result = false
+    else:
+      raiseOSError(osLastError(), dir)
+  elif defined(haiku):
+    let res = mkdir(dir, 0o777)
+    if res == 0'i32:
+      result = true
+    elif errno == EEXIST or errno == EROFS:
+      result = false
+    else:
+      raiseOSError(osLastError(), dir)
+  elif defined(posix):
+    let res = mkdir(dir, 0o777)
+    if res == 0'i32:
+      result = true
+    elif errno == EEXIST:
+      result = false
+    else:
+      #echo res
+      raiseOSError(osLastError(), dir)
+  else:
+    wrapUnary(res, createDirectoryW, dir)
+
+    if res != 0'i32:
+      result = true
+    elif getLastError() == 183'i32:
+      result = false
+    else:
+      raiseOSError(osLastError(), dir)
+
+proc existsOrCreateDir*(dir: string): bool {.rtl, extern: "nos$1",
+  tags: [WriteDirEffect, ReadDirEffect], noWeirdTarget.} =
+  ## Checks if a `directory`:idx: `dir` exists, and creates it otherwise.
+  ##
+  ## Does not create parent directories (raises `OSError` if parent directories do not exist).
+  ## Returns `true` if the directory already exists, and `false` otherwise.
+  ##
+  ## See also:
+  ## * `removeDir proc`_
+  ## * `createDir proc`_
+  ## * `copyDir proc`_
+  ## * `copyDirWithPermissions proc`_
+  ## * `moveDir proc`_
+  result = not rawCreateDir(dir)
+  if result:
+    # path already exists - need to check that it is indeed a directory
+    if not dirExists(dir):
+      raise newException(IOError, "Failed to create '" & dir & "'")
+
+proc createDir*(dir: string) {.rtl, extern: "nos$1",
+  tags: [WriteDirEffect, ReadDirEffect], noWeirdTarget.} =
+  ## Creates the `directory`:idx: `dir`.
+  ##
+  ## The directory may contain several subdirectories that do not exist yet.
+  ## The full path is created. If this fails, `OSError` is raised.
+  ##
+  ## It does **not** fail if the directory already exists because for
+  ## most usages this does not indicate an error.
+  ##
+  ## See also:
+  ## * `removeDir proc`_
+  ## * `existsOrCreateDir proc`_
+  ## * `copyDir proc`_
+  ## * `copyDirWithPermissions proc`_
+  ## * `moveDir proc`_
+  if dir == "":
+    return
+  var omitNext = isAbsolute(dir)
+  for p in parentDirs(dir, fromRoot=true):
+    if omitNext:
+      omitNext = false
+    else:
+      discard existsOrCreateDir(p)
+
+proc copyDir*(source, dest: string, skipSpecial = false) {.rtl, extern: "nos$1",
+  tags: [ReadDirEffect, WriteIOEffect, ReadIOEffect], benign, noWeirdTarget.} =
+  ## Copies a directory from `source` to `dest`.
+  ##
+  ## On non-Windows OSes, symlinks are copied as symlinks. On Windows, symlinks
+  ## are skipped.
+  ##
+  ## If `skipSpecial` is true, then (besides all directories) only *regular*
+  ## files (**without** special "file" objects like FIFOs, device files,
+  ## etc) will be copied on Unix.
+  ##
+  ## If this fails, `OSError` is raised.
+  ##
+  ## On the Windows platform this proc will copy the attributes from
+  ## `source` into `dest`.
+  ##
+  ## On other platforms created files and directories will inherit the
+  ## default permissions of a newly created file/directory for the user.
+  ## Use `copyDirWithPermissions proc`_
+  ## to preserve attributes recursively on these platforms.
+  ##
+  ## See also:
+  ## * `copyDirWithPermissions proc`_
+  ## * `copyFile proc`_
+  ## * `copyFileWithPermissions proc`_
+  ## * `removeDir proc`_
+  ## * `existsOrCreateDir proc`_
+  ## * `createDir proc`_
+  ## * `moveDir proc`_
+  createDir(dest)
+  for kind, path in walkDir(source, skipSpecial = skipSpecial):
+    var noSource = splitPath(path).tail
+    if kind == pcDir:
+      copyDir(path, dest / noSource, skipSpecial = skipSpecial)
+    else:
+      copyFile(path, dest / noSource, {cfSymlinkAsIs})
+
+
+proc copyDirWithPermissions*(source, dest: string,
+                             ignorePermissionErrors = true,
+                             skipSpecial = false)
+  {.rtl, extern: "nos$1", tags: [ReadDirEffect, WriteIOEffect, ReadIOEffect],
+   benign, noWeirdTarget.} =
+  ## Copies a directory from `source` to `dest` preserving file permissions.
+  ##
+  ## On non-Windows OSes, symlinks are copied as symlinks. On Windows, symlinks
+  ## are skipped.
+  ##
+  ## If `skipSpecial` is true, then (besides all directories) only *regular*
+  ## files (**without** special "file" objects like FIFOs, device files,
+  ## etc) will be copied on Unix.
+  ##
+  ## If this fails, `OSError` is raised. This is a wrapper proc around
+  ## `copyDir`_ and `copyFileWithPermissions`_ procs
+  ## on non-Windows platforms.
+  ##
+  ## On Windows this proc is just a wrapper for `copyDir proc`_ since
+  ## that proc already copies attributes.
+  ##
+  ## On non-Windows systems permissions are copied after the file or directory
+  ## itself has been copied, which won't happen atomically and could lead to a
+  ## race condition. If `ignorePermissionErrors` is true (default), errors while
+  ## reading/setting file attributes will be ignored, otherwise will raise
+  ## `OSError`.
+  ##
+  ## See also:
+  ## * `copyDir proc`_
+  ## * `copyFile proc`_
+  ## * `copyFileWithPermissions proc`_
+  ## * `removeDir proc`_
+  ## * `moveDir proc`_
+  ## * `existsOrCreateDir proc`_
+  ## * `createDir proc`_
+  createDir(dest)
+  when not defined(windows):
+    try:
+      setFilePermissions(dest, getFilePermissions(source), followSymlinks =
+                         false)
+    except:
+      if not ignorePermissionErrors:
+        raise
+  for kind, path in walkDir(source, skipSpecial = skipSpecial):
+    var noSource = splitPath(path).tail
+    if kind == pcDir:
+      copyDirWithPermissions(path, dest / noSource, ignorePermissionErrors, skipSpecial = skipSpecial)
+    else:
+      copyFileWithPermissions(path, dest / noSource, ignorePermissionErrors, {cfSymlinkAsIs})
+
+proc moveDir*(source, dest: string) {.tags: [ReadIOEffect, WriteIOEffect], noWeirdTarget.} =
+  ## Moves a directory from `source` to `dest`.
+  ##
+  ## Symlinks are not followed: if `source` contains symlinks, they themself are
+  ## moved, not their target.
+  ##
+  ## If this fails, `OSError` is raised.
+  ##
+  ## See also:
+  ## * `moveFile proc`_
+  ## * `copyDir proc`_
+  ## * `copyDirWithPermissions proc`_
+  ## * `removeDir proc`_
+  ## * `existsOrCreateDir proc`_
+  ## * `createDir proc`_
+  if not tryMoveFSObject(source, dest, isDir = true):
+    # Fallback to copy & del
+    copyDir(source, dest)
+    removeDir(source)
+
+proc setCurrentDir*(newDir: string) {.inline, tags: [], noWeirdTarget.} =
+  ## Sets the `current working directory`:idx:; `OSError`
+  ## is raised if `newDir` cannot been set.
+  ##
+  ## See also:
+  ## * `getHomeDir proc`_
+  ## * `getConfigDir proc`_
+  ## * `getTempDir proc`_
+  ## * `getCurrentDir proc`_
+  when defined(windows):
+    if setCurrentDirectoryW(newWideCString(newDir)) == 0'i32:
+      raiseOSError(osLastError(), newDir)
+  else:
+    if chdir(newDir) != 0'i32: raiseOSError(osLastError(), newDir)
diff --git a/lib/std/private/osfiles.nim b/lib/std/private/osfiles.nim
new file mode 100644
index 000000000..37d8eabca
--- /dev/null
+++ b/lib/std/private/osfiles.nim
@@ -0,0 +1,416 @@
+include system/inclrtl
+import std/private/since
+import std/oserrors
+
+import oscommon
+export fileExists
+
+import ospaths2, ossymlinks
+
+## .. importdoc:: osdirs.nim, os.nim
+
+when defined(nimPreviewSlimSystem):
+  import std/[syncio, assertions, widestrs]
+
+when weirdTarget:
+  discard
+elif defined(windows):
+  import std/winlean
+elif defined(posix):
+  import std/[posix, times]
+
+  proc toTime(ts: Timespec): times.Time {.inline.} =
+    result = initTime(ts.tv_sec.int64, ts.tv_nsec.int)
+else:
+  {.error: "OS module not ported to your operating system!".}
+
+
+when weirdTarget:
+  {.pragma: noWeirdTarget, error: "this proc is not available on the NimScript/js target".}
+else:
+  {.pragma: noWeirdTarget.}
+
+
+when defined(nimscript):
+  # for procs already defined in scriptconfig.nim
+  template noNimJs(body): untyped = discard
+elif defined(js):
+  {.pragma: noNimJs, error: "this proc is not available on the js target".}
+else:
+  {.pragma: noNimJs.}
+
+
+type
+  FilePermission* = enum   ## File access permission, modelled after UNIX.
+    ##
+    ## See also:
+    ## * `getFilePermissions`_
+    ## * `setFilePermissions`_
+    ## * `FileInfo object`_
+    fpUserExec,            ## execute access for the file owner
+    fpUserWrite,           ## write access for the file owner
+    fpUserRead,            ## read access for the file owner
+    fpGroupExec,           ## execute access for the group
+    fpGroupWrite,          ## write access for the group
+    fpGroupRead,           ## read access for the group
+    fpOthersExec,          ## execute access for others
+    fpOthersWrite,         ## write access for others
+    fpOthersRead           ## read access for others
+
+proc getFilePermissions*(filename: string): set[FilePermission] {.
+  rtl, extern: "nos$1", tags: [ReadDirEffect], noWeirdTarget.} =
+  ## Retrieves file permissions for `filename`.
+  ##
+  ## `OSError` is raised in case of an error.
+  ## On Windows, only the ``readonly`` flag is checked, every other
+  ## permission is available in any case.
+  ##
+  ## See also:
+  ## * `setFilePermissions proc`_
+  ## * `FilePermission enum`_
+  when defined(posix):
+    var a: Stat
+    if stat(filename, a) < 0'i32: raiseOSError(osLastError(), filename)
+    result = {}
+    if (a.st_mode and S_IRUSR.Mode) != 0.Mode: result.incl(fpUserRead)
+    if (a.st_mode and S_IWUSR.Mode) != 0.Mode: result.incl(fpUserWrite)
+    if (a.st_mode and S_IXUSR.Mode) != 0.Mode: result.incl(fpUserExec)
+
+    if (a.st_mode and S_IRGRP.Mode) != 0.Mode: result.incl(fpGroupRead)
+    if (a.st_mode and S_IWGRP.Mode) != 0.Mode: result.incl(fpGroupWrite)
+    if (a.st_mode and S_IXGRP.Mode) != 0.Mode: result.incl(fpGroupExec)
+
+    if (a.st_mode and S_IROTH.Mode) != 0.Mode: result.incl(fpOthersRead)
+    if (a.st_mode and S_IWOTH.Mode) != 0.Mode: result.incl(fpOthersWrite)
+    if (a.st_mode and S_IXOTH.Mode) != 0.Mode: result.incl(fpOthersExec)
+  else:
+    wrapUnary(res, getFileAttributesW, filename)
+    if res == -1'i32: raiseOSError(osLastError(), filename)
+    if (res and FILE_ATTRIBUTE_READONLY) != 0'i32:
+      result = {fpUserExec, fpUserRead, fpGroupExec, fpGroupRead,
+                fpOthersExec, fpOthersRead}
+    else:
+      result = {fpUserExec..fpOthersRead}
+
+proc setFilePermissions*(filename: string, permissions: set[FilePermission],
+                         followSymlinks = true)
+  {.rtl, extern: "nos$1", tags: [ReadDirEffect, WriteDirEffect],
+   noWeirdTarget.} =
+  ## Sets the file permissions for `filename`.
+  ##
+  ## If `followSymlinks` set to true (default) and ``filename`` points to a
+  ## symlink, permissions are set to the file symlink points to.
+  ## `followSymlinks` set to false is a noop on Windows and some POSIX
+  ## systems (including Linux) on which `lchmod` is either unavailable or always
+  ## fails, given that symlinks permissions there are not observed.
+  ##
+  ## `OSError` is raised in case of an error.
+  ## On Windows, only the ``readonly`` flag is changed, depending on
+  ## ``fpUserWrite`` permission.
+  ##
+  ## See also:
+  ## * `getFilePermissions proc`_
+  ## * `FilePermission enum`_
+  when defined(posix):
+    var p = 0.Mode
+    if fpUserRead in permissions: p = p or S_IRUSR.Mode
+    if fpUserWrite in permissions: p = p or S_IWUSR.Mode
+    if fpUserExec in permissions: p = p or S_IXUSR.Mode
+
+    if fpGroupRead in permissions: p = p or S_IRGRP.Mode
+    if fpGroupWrite in permissions: p = p or S_IWGRP.Mode
+    if fpGroupExec in permissions: p = p or S_IXGRP.Mode
+
+    if fpOthersRead in permissions: p = p or S_IROTH.Mode
+    if fpOthersWrite in permissions: p = p or S_IWOTH.Mode
+    if fpOthersExec in permissions: p = p or S_IXOTH.Mode
+
+    if not followSymlinks and filename.symlinkExists:
+      when declared(lchmod):
+        if lchmod(filename, cast[Mode](p)) != 0:
+          raiseOSError(osLastError(), $(filename, permissions))
+    else:
+      if chmod(filename, cast[Mode](p)) != 0:
+        raiseOSError(osLastError(), $(filename, permissions))
+  else:
+    wrapUnary(res, getFileAttributesW, filename)
+    if res == -1'i32: raiseOSError(osLastError(), filename)
+    if fpUserWrite in permissions:
+      res = res and not FILE_ATTRIBUTE_READONLY
+    else:
+      res = res or FILE_ATTRIBUTE_READONLY
+    wrapBinary(res2, setFileAttributesW, filename, res)
+    if res2 == - 1'i32: raiseOSError(osLastError(), $(filename, permissions))
+
+
+const hasCCopyfile = defined(osx) and not defined(nimLegacyCopyFile)
+  # xxx instead of `nimLegacyCopyFile`, support something like: `when osxVersion >= (10, 5)`
+
+when hasCCopyfile:
+  # `copyfile` API available since osx 10.5.
+  {.push nodecl, header: "<copyfile.h>".}
+  type
+    copyfile_state_t {.nodecl.} = pointer
+    copyfile_flags_t = cint
+  proc copyfile_state_alloc(): copyfile_state_t
+  proc copyfile_state_free(state: copyfile_state_t): cint
+  proc c_copyfile(src, dst: cstring,  state: copyfile_state_t, flags: copyfile_flags_t): cint {.importc: "copyfile".}
+  when (NimMajor, NimMinor) >= (1, 4):
+    let
+      COPYFILE_DATA {.nodecl.}: copyfile_flags_t
+      COPYFILE_XATTR {.nodecl.}: copyfile_flags_t
+  else:
+    var
+      COPYFILE_DATA {.nodecl.}: copyfile_flags_t
+      COPYFILE_XATTR {.nodecl.}: copyfile_flags_t
+  {.pop.}
+
+type
+  CopyFlag* = enum    ## Copy options.
+    cfSymlinkAsIs,    ## Copy symlinks as symlinks
+    cfSymlinkFollow,  ## Copy the files symlinks point to
+    cfSymlinkIgnore   ## Ignore symlinks
+
+const copyFlagSymlink = {cfSymlinkAsIs, cfSymlinkFollow, cfSymlinkIgnore}
+
+proc copyFile*(source, dest: string, options = {cfSymlinkFollow}; bufferSize = 16_384) {.rtl,
+  extern: "nos$1", tags: [ReadDirEffect, ReadIOEffect, WriteIOEffect],
+  noWeirdTarget.} =
+  ## Copies a file from `source` to `dest`, where `dest.parentDir` must exist.
+  ##
+  ## On non-Windows OSes, `options` specify the way file is copied; by default,
+  ## if `source` is a symlink, copies the file symlink points to. `options` is
+  ## ignored on Windows: symlinks are skipped.
+  ##
+  ## If this fails, `OSError` is raised.
+  ##
+  ## On the Windows platform this proc will
+  ## copy the source file's attributes into dest.
+  ##
+  ## On other platforms you need
+  ## to use `getFilePermissions`_ and
+  ## `setFilePermissions`_
+  ## procs
+  ## to copy them by hand (or use the convenience `copyFileWithPermissions
+  ## proc`_),
+  ## otherwise `dest` will inherit the default permissions of a newly
+  ## created file for the user.
+  ##
+  ## If `dest` already exists, the file attributes
+  ## will be preserved and the content overwritten.
+  ##
+  ## On OSX, `copyfile` C api will be used (available since OSX 10.5) unless
+  ## `-d:nimLegacyCopyFile` is used.
+  ##
+  ## `copyFile` allows to specify `bufferSize` to improve I/O performance.
+  ##
+  ## See also:
+  ## * `CopyFlag enum`_
+  ## * `copyDir proc`_
+  ## * `copyFileWithPermissions proc`_
+  ## * `tryRemoveFile proc`_
+  ## * `removeFile proc`_
+  ## * `moveFile proc`_
+
+  doAssert card(copyFlagSymlink * options) == 1, "There should be exactly one cfSymlink* in options"
+  let isSymlink = source.symlinkExists
+  if isSymlink and (cfSymlinkIgnore in options or defined(windows)):
+    return
+  when defined(windows):
+    let s = newWideCString(source)
+    let d = newWideCString(dest)
+    if copyFileW(s, d, 0'i32) == 0'i32:
+      raiseOSError(osLastError(), $(source, dest))
+  else:
+    if isSymlink and cfSymlinkAsIs in options:
+      createSymlink(expandSymlink(source), dest)
+    else:
+      when hasCCopyfile:
+        let state = copyfile_state_alloc()
+        # xxx `COPYFILE_STAT` could be used for one-shot
+        # `copyFileWithPermissions`.
+        let status = c_copyfile(source.cstring, dest.cstring, state,
+                                COPYFILE_DATA)
+        if status != 0:
+          let err = osLastError()
+          discard copyfile_state_free(state)
+          raiseOSError(err, $(source, dest))
+        let status2 = copyfile_state_free(state)
+        if status2 != 0: raiseOSError(osLastError(), $(source, dest))
+      else:
+        # generic version of copyFile which works for any platform:
+        var d, s: File
+        if not open(s, source): raiseOSError(osLastError(), source)
+        if not open(d, dest, fmWrite):
+          close(s)
+          raiseOSError(osLastError(), dest)
+
+        # Hints for kernel-level aggressive sequential low-fragmentation read-aheads:
+        # https://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_fadvise.html
+        when defined(linux) or defined(osx):
+          discard posix_fadvise(getFileHandle(d), 0.cint, 0.cint, POSIX_FADV_SEQUENTIAL)
+          discard posix_fadvise(getFileHandle(s), 0.cint, 0.cint, POSIX_FADV_SEQUENTIAL)
+
+        var buf = alloc(bufferSize)
+        while true:
+          var bytesread = readBuffer(s, buf, bufferSize)
+          if bytesread > 0:
+            var byteswritten = writeBuffer(d, buf, bytesread)
+            if bytesread != byteswritten:
+              dealloc(buf)
+              close(s)
+              close(d)
+              raiseOSError(osLastError(), dest)
+          if bytesread != bufferSize: break
+        dealloc(buf)
+        close(s)
+        flushFile(d)
+        close(d)
+
+proc copyFileToDir*(source, dir: string, options = {cfSymlinkFollow}; bufferSize = 16_384)
+  {.noWeirdTarget, since: (1,3,7).} =
+  ## Copies a file `source` into directory `dir`, which must exist.
+  ##
+  ## On non-Windows OSes, `options` specify the way file is copied; by default,
+  ## if `source` is a symlink, copies the file symlink points to. `options` is
+  ## ignored on Windows: symlinks are skipped.
+  ##
+  ## `copyFileToDir` allows to specify `bufferSize` to improve I/O performance.
+  ##
+  ## See also:
+  ## * `CopyFlag enum`_
+  ## * `copyFile proc`_
+  if dir.len == 0: # treating "" as "." is error prone
+    raise newException(ValueError, "dest is empty")
+  copyFile(source, dir / source.lastPathPart, options, bufferSize)
+
+
+proc copyFileWithPermissions*(source, dest: string,
+                              ignorePermissionErrors = true,
+                              options = {cfSymlinkFollow}) {.noWeirdTarget.} =
+  ## Copies a file from `source` to `dest` preserving file permissions.
+  ##
+  ## On non-Windows OSes, `options` specify the way file is copied; by default,
+  ## if `source` is a symlink, copies the file symlink points to. `options` is
+  ## ignored on Windows: symlinks are skipped.
+  ##
+  ## This is a wrapper proc around `copyFile`_,
+  ## `getFilePermissions`_ and `setFilePermissions`_
+  ## procs on non-Windows platforms.
+  ##
+  ## On Windows this proc is just a wrapper for `copyFile proc`_ since
+  ## that proc already copies attributes.
+  ##
+  ## On non-Windows systems permissions are copied after the file itself has
+  ## been copied, which won't happen atomically and could lead to a race
+  ## condition. If `ignorePermissionErrors` is true (default), errors while
+  ## reading/setting file attributes will be ignored, otherwise will raise
+  ## `OSError`.
+  ##
+  ## See also:
+  ## * `CopyFlag enum`_
+  ## * `copyFile proc`_
+  ## * `copyDir proc`_
+  ## * `tryRemoveFile proc`_
+  ## * `removeFile proc`_
+  ## * `moveFile proc`_
+  ## * `copyDirWithPermissions proc`_
+  copyFile(source, dest, options)
+  when not defined(windows):
+    try:
+      setFilePermissions(dest, getFilePermissions(source), followSymlinks =
+                         (cfSymlinkFollow in options))
+    except:
+      if not ignorePermissionErrors:
+        raise
+
+when not declared(ENOENT) and not defined(windows):
+  when defined(nimscript):
+    when not defined(haiku):
+      const ENOENT = cint(2) # 2 on most systems including Solaris
+    else:
+      const ENOENT = cint(-2147459069)
+  else:
+    var ENOENT {.importc, header: "<errno.h>".}: cint
+
+when defined(windows) and not weirdTarget:
+  template deleteFile(file: untyped): untyped  = deleteFileW(file)
+  template setFileAttributes(file, attrs: untyped): untyped =
+    setFileAttributesW(file, attrs)
+
+proc tryRemoveFile*(file: string): bool {.rtl, extern: "nos$1", tags: [WriteDirEffect], noWeirdTarget.} =
+  ## Removes the `file`.
+  ##
+  ## If this fails, returns `false`. This does not fail
+  ## if the file never existed in the first place.
+  ##
+  ## On Windows, ignores the read-only attribute.
+  ##
+  ## See also:
+  ## * `copyFile proc`_
+  ## * `copyFileWithPermissions proc`_
+  ## * `removeFile proc`_
+  ## * `moveFile proc`_
+  result = true
+  when defined(windows):
+    let f = newWideCString(file)
+    if deleteFile(f) == 0:
+      result = false
+      let err = getLastError()
+      if err == ERROR_FILE_NOT_FOUND or err == ERROR_PATH_NOT_FOUND:
+        result = true
+      elif err == ERROR_ACCESS_DENIED and
+         setFileAttributes(f, FILE_ATTRIBUTE_NORMAL) != 0 and
+         deleteFile(f) != 0:
+        result = true
+  else:
+    if unlink(file) != 0'i32 and errno != ENOENT:
+      result = false
+
+proc removeFile*(file: string) {.rtl, extern: "nos$1", tags: [WriteDirEffect], noWeirdTarget.} =
+  ## Removes the `file`.
+  ##
+  ## If this fails, `OSError` is raised. This does not fail
+  ## if the file never existed in the first place.
+  ##
+  ## On Windows, ignores the read-only attribute.
+  ##
+  ## See also:
+  ## * `removeDir proc`_
+  ## * `copyFile proc`_
+  ## * `copyFileWithPermissions proc`_
+  ## * `tryRemoveFile proc`_
+  ## * `moveFile proc`_
+  if not tryRemoveFile(file):
+    raiseOSError(osLastError(), file)
+
+proc moveFile*(source, dest: string) {.rtl, extern: "nos$1",
+  tags: [ReadDirEffect, ReadIOEffect, WriteIOEffect], noWeirdTarget.} =
+  ## Moves a file from `source` to `dest`.
+  ##
+  ## Symlinks are not followed: if `source` is a symlink, it is itself moved,
+  ## not its target.
+  ##
+  ## If this fails, `OSError` is raised.
+  ## If `dest` already exists, it will be overwritten.
+  ##
+  ## Can be used to `rename files`:idx:.
+  ##
+  ## See also:
+  ## * `moveDir proc`_
+  ## * `copyFile proc`_
+  ## * `copyFileWithPermissions proc`_
+  ## * `removeFile proc`_
+  ## * `tryRemoveFile proc`_
+
+  if not tryMoveFSObject(source, dest, isDir = false):
+    when defined(windows):
+      raiseAssert "unreachable"
+    else:
+      # Fallback to copy & del
+      copyFileWithPermissions(source, dest, options={cfSymlinkAsIs})
+      try:
+        removeFile(source)
+      except:
+        discard tryRemoveFile(dest)
+        raise
diff --git a/lib/std/private/ospaths2.nim b/lib/std/private/ospaths2.nim
new file mode 100644
index 000000000..bc69ff725
--- /dev/null
+++ b/lib/std/private/ospaths2.nim
@@ -0,0 +1,1030 @@
+include system/inclrtl
+import std/private/since
+
+import std/[strutils, pathnorm]
+import std/oserrors
+
+import oscommon
+export ReadDirEffect, WriteDirEffect
+
+when defined(nimPreviewSlimSystem):
+  import std/[syncio, assertions, widestrs]
+
+## .. importdoc:: osappdirs.nim, osdirs.nim, osseps.nim, os.nim
+
+const weirdTarget = defined(nimscript) or defined(js)
+
+when weirdTarget:
+  discard
+elif defined(windows):
+  import std/winlean
+elif defined(posix):
+  import std/posix, system/ansi_c
+else:
+  {.error: "OS module not ported to your operating system!".}
+
+when weirdTarget:
+  {.pragma: noWeirdTarget, error: "this proc is not available on the NimScript/js target".}
+else:
+  {.pragma: noWeirdTarget.}
+
+when defined(nimscript):
+  # for procs already defined in scriptconfig.nim
+  template noNimJs(body): untyped = discard
+elif defined(js):
+  {.pragma: noNimJs, error: "this proc is not available on the js target".}
+else:
+  {.pragma: noNimJs.}
+
+
+proc normalizePathAux(path: var string){.inline, raises: [], noSideEffect.}
+
+
+import std/private/osseps
+export osseps
+
+proc absolutePathInternal(path: string): string {.gcsafe.}
+
+proc normalizePathEnd*(path: var string, trailingSep = false) =
+  ## Ensures ``path`` has exactly 0 or 1 trailing `DirSep`, depending on
+  ## ``trailingSep``, and taking care of edge cases: it preservers whether
+  ## a path is absolute or relative, and makes sure trailing sep is `DirSep`,
+  ## not `AltSep`. Trailing `/.` are compressed, see examples.
+  if path.len == 0: return
+  var i = path.len
+  while i >= 1:
+    if path[i-1] in {DirSep, AltSep}: dec(i)
+    elif path[i-1] == '.' and i >= 2 and path[i-2] in {DirSep, AltSep}: dec(i)
+    else: break
+  if trailingSep:
+    # foo// => foo
+    path.setLen(i)
+    # foo => foo/
+    path.add DirSep
+  elif i > 0:
+    # foo// => foo
+    path.setLen(i)
+  else:
+    # // => / (empty case was already taken care of)
+    path = $DirSep
+
+proc normalizePathEnd*(path: string, trailingSep = false): string =
+  ## outplace overload
+  runnableExamples:
+    when defined(posix):
+      assert normalizePathEnd("/lib//.//", trailingSep = true) == "/lib/"
+      assert normalizePathEnd("lib/./.", trailingSep = false) == "lib"
+      assert normalizePathEnd(".//./.", trailingSep = false) == "."
+      assert normalizePathEnd("", trailingSep = true) == "" # not / !
+      assert normalizePathEnd("/", trailingSep = false) == "/" # not "" !
+  result = path
+  result.normalizePathEnd(trailingSep)
+
+template endsWith(a: string, b: set[char]): bool =
+  a.len > 0 and a[^1] in b
+
+proc joinPathImpl(result: var string, state: var int, tail: string) =
+  let trailingSep = tail.endsWith({DirSep, AltSep}) or tail.len == 0 and result.endsWith({DirSep, AltSep})
+  normalizePathEnd(result, trailingSep=false)
+  addNormalizePath(tail, result, state, DirSep)
+  normalizePathEnd(result, trailingSep=trailingSep)
+
+proc joinPath*(head, tail: string): string {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Joins two directory names to one.
+  ##
+  ## returns normalized path concatenation of `head` and `tail`, preserving
+  ## whether or not `tail` has a trailing slash (or, if tail if empty, whether
+  ## head has one).
+  ##
+  ## See also:
+  ## * `joinPath(parts: varargs[string]) proc`_
+  ## * `/ proc`_
+  ## * `splitPath proc`_
+  ## * `uri.combine proc <uri.html#combine,Uri,Uri>`_
+  ## * `uri./ proc <uri.html#/,Uri,string>`_
+  runnableExamples:
+    when defined(posix):
+      assert joinPath("usr", "lib") == "usr/lib"
+      assert joinPath("usr", "lib/") == "usr/lib/"
+      assert joinPath("usr", "") == "usr"
+      assert joinPath("usr/", "") == "usr/"
+      assert joinPath("", "") == ""
+      assert joinPath("", "lib") == "lib"
+      assert joinPath("", "/lib") == "/lib"
+      assert joinPath("usr/", "/lib") == "usr/lib"
+      assert joinPath("usr/lib", "../bin") == "usr/bin"
+
+  result = newStringOfCap(head.len + tail.len)
+  var state = 0
+  joinPathImpl(result, state, head)
+  joinPathImpl(result, state, tail)
+  when false:
+    if len(head) == 0:
+      result = tail
+    elif head[len(head)-1] in {DirSep, AltSep}:
+      if tail.len > 0 and tail[0] in {DirSep, AltSep}:
+        result = head & substr(tail, 1)
+      else:
+        result = head & tail
+    else:
+      if tail.len > 0 and tail[0] in {DirSep, AltSep}:
+        result = head & tail
+      else:
+        result = head & DirSep & tail
+
+proc joinPath*(parts: varargs[string]): string {.noSideEffect,
+  rtl, extern: "nos$1OpenArray".} =
+  ## The same as `joinPath(head, tail) proc`_,
+  ## but works with any number of directory parts.
+  ##
+  ## You need to pass at least one element or the proc
+  ## will assert in debug builds and crash on release builds.
+  ##
+  ## See also:
+  ## * `joinPath(head, tail) proc`_
+  ## * `/ proc`_
+  ## * `/../ proc`_
+  ## * `splitPath proc`_
+  runnableExamples:
+    when defined(posix):
+      assert joinPath("a") == "a"
+      assert joinPath("a", "b", "c") == "a/b/c"
+      assert joinPath("usr/lib", "../../var", "log") == "var/log"
+
+  var estimatedLen = 0
+  for p in parts: estimatedLen += p.len
+  result = newStringOfCap(estimatedLen)
+  var state = 0
+  for i in 0..high(parts):
+    joinPathImpl(result, state, parts[i])
+
+proc `/`*(head, tail: string): string {.noSideEffect, inline.} =
+  ## The same as `joinPath(head, tail) proc`_.
+  ##
+  ## See also:
+  ## * `/../ proc`_
+  ## * `joinPath(head, tail) proc`_
+  ## * `joinPath(parts: varargs[string]) proc`_
+  ## * `splitPath proc`_
+  ## * `uri.combine proc <uri.html#combine,Uri,Uri>`_
+  ## * `uri./ proc <uri.html#/,Uri,string>`_
+  runnableExamples:
+    when defined(posix):
+      assert "usr" / "" == "usr"
+      assert "" / "lib" == "lib"
+      assert "" / "/lib" == "/lib"
+      assert "usr/" / "/lib/" == "usr/lib/"
+      assert "usr" / "lib" / "../bin" == "usr/bin"
+
+  result = joinPath(head, tail)
+
+when doslikeFileSystem:
+  import std/private/ntpath
+
+proc splitPath*(path: string): tuple[head, tail: string] {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Splits a directory into `(head, tail)` tuple, so that
+  ## ``head / tail == path`` (except for edge cases like "/usr").
+  ##
+  ## See also:
+  ## * `joinPath(head, tail) proc`_
+  ## * `joinPath(parts: varargs[string]) proc`_
+  ## * `/ proc`_
+  ## * `/../ proc`_
+  ## * `relativePath proc`_
+  runnableExamples:
+    assert splitPath("usr/local/bin") == ("usr/local", "bin")
+    assert splitPath("usr/local/bin/") == ("usr/local/bin", "")
+    assert splitPath("/bin/") == ("/bin", "")
+    when (NimMajor, NimMinor) <= (1, 0):
+      assert splitPath("/bin") == ("", "bin")
+    else:
+      assert splitPath("/bin") == ("/", "bin")
+    assert splitPath("bin") == ("", "bin")
+    assert splitPath("") == ("", "")
+
+  when doslikeFileSystem:
+    let (drive, splitpath) = splitDrive(path)
+    let stop = drive.len
+  else:
+    const stop = 0
+
+  var sepPos = -1
+  for i in countdown(len(path)-1, stop):
+    if path[i] in {DirSep, AltSep}:
+      sepPos = i
+      break
+  if sepPos >= 0:
+    result.head = substr(path, 0,
+      when (NimMajor, NimMinor) <= (1, 0):
+        sepPos-1
+      else:
+        if likely(sepPos >= 1): sepPos-1 else: 0
+    )
+    result.tail = substr(path, sepPos+1)
+  else:
+    when doslikeFileSystem:
+      result.head = drive
+      result.tail = splitpath
+    else:
+      result.head = ""
+      result.tail = path
+
+proc isAbsolute*(path: string): bool {.rtl, noSideEffect, extern: "nos$1", raises: [].} =
+  ## Checks whether a given `path` is absolute.
+  ##
+  ## On Windows, network paths are considered absolute too.
+  runnableExamples:
+    assert not "".isAbsolute
+    assert not ".".isAbsolute
+    when defined(posix):
+      assert "/".isAbsolute
+      assert not "a/".isAbsolute
+      assert "/a/".isAbsolute
+
+  if len(path) == 0: return false
+
+  when doslikeFileSystem:
+    var len = len(path)
+    result = (path[0] in {'/', '\\'}) or
+              (len > 1 and path[0] in {'a'..'z', 'A'..'Z'} and path[1] == ':')
+  elif defined(macos):
+    # according to https://perldoc.perl.org/File/Spec/Mac.html `:a` is a relative path
+    result = path[0] != ':'
+  elif defined(RISCOS):
+    result = path[0] == '$'
+  elif defined(posix):
+    result = path[0] == '/'
+  elif defined(nodejs):
+    {.emit: [result," = require(\"path\").isAbsolute(",path.cstring,");"].}
+  else:
+    raiseAssert "unreachable" # if ever hits here, adapt as needed
+
+when FileSystemCaseSensitive:
+  template `!=?`(a, b: char): bool = a != b
+else:
+  template `!=?`(a, b: char): bool = toLowerAscii(a) != toLowerAscii(b)
+
+when doslikeFileSystem:
+  proc isAbsFromCurrentDrive(path: string): bool {.noSideEffect, raises: [].} =
+    ## An absolute path from the root of the current drive (e.g. "\foo")
+    path.len > 0 and
+    (path[0] == AltSep or
+     (path[0] == DirSep and
+      (path.len == 1 or path[1] notin {DirSep, AltSep, ':'})))
+
+  proc sameRoot(path1, path2: string): bool {.noSideEffect, raises: [].} =
+    ## Return true if path1 and path2 have a same root.
+    ##
+    ## Detail of Windows path formats:
+    ## https://docs.microsoft.com/en-us/dotnet/standard/io/file-path-formats
+
+    assert(isAbsolute(path1))
+    assert(isAbsolute(path2))
+
+    if isAbsFromCurrentDrive(path1) and isAbsFromCurrentDrive(path2):
+      result = true
+    elif cmpIgnoreCase(splitDrive(path1).drive, splitDrive(path2).drive) == 0:
+      result = true
+    else:
+      result = false
+
+proc relativePath*(path, base: string, sep = DirSep): string {.
+  rtl, extern: "nos$1".} =
+  ## Converts `path` to a path relative to `base`.
+  ##
+  ## The `sep` (default: DirSep_) is used for the path normalizations,
+  ## this can be useful to ensure the relative path only contains `'/'`
+  ## so that it can be used for URL constructions.
+  ##
+  ## On Windows, if a root of `path` and a root of `base` are different,
+  ## returns `path` as is because it is impossible to make a relative path.
+  ## That means an absolute path can be returned.
+  ##
+  ## See also:
+  ## * `splitPath proc`_
+  ## * `parentDir proc`_
+  ## * `tailDir proc`_
+  runnableExamples:
+    assert relativePath("/Users/me/bar/z.nim", "/Users/other/bad", '/') == "../../me/bar/z.nim"
+    assert relativePath("/Users/me/bar/z.nim", "/Users/other", '/') == "../me/bar/z.nim"
+    when not doslikeFileSystem: # On Windows, UNC-paths start with `//`
+      assert relativePath("/Users///me/bar//z.nim", "//Users/", '/') == "me/bar/z.nim"
+    assert relativePath("/Users/me/bar/z.nim", "/Users/me", '/') == "bar/z.nim"
+    assert relativePath("", "/users/moo", '/') == ""
+    assert relativePath("foo", ".", '/') == "foo"
+    assert relativePath("foo", "foo", '/') == "."
+
+  if path.len == 0: return ""
+  var base = if base == ".": "" else: base
+  var path = path
+  path.normalizePathAux
+  base.normalizePathAux
+  let a1 = isAbsolute(path)
+  let a2 = isAbsolute(base)
+  if a1 and not a2:
+    base = absolutePathInternal(base)
+  elif a2 and not a1:
+    path = absolutePathInternal(path)
+
+  when doslikeFileSystem:
+    if isAbsolute(path) and isAbsolute(base):
+      if not sameRoot(path, base):
+        return path
+
+  var f = default PathIter
+  var b = default PathIter
+  var ff = (0, -1)
+  var bb = (0, -1) # (int, int)
+  result = newStringOfCap(path.len)
+  # skip the common prefix:
+  while f.hasNext(path) and b.hasNext(base):
+    ff = next(f, path)
+    bb = next(b, base)
+    let diff = ff[1] - ff[0]
+    if diff != bb[1] - bb[0]: break
+    var same = true
+    for i in 0..diff:
+      if path[i + ff[0]] !=? base[i + bb[0]]:
+        same = false
+        break
+    if not same: break
+    ff = (0, -1)
+    bb = (0, -1)
+  #  for i in 0..diff:
+  #    result.add base[i + bb[0]]
+
+  # /foo/bar/xxx/ -- base
+  # /foo/bar/baz  -- path path
+  #   ../baz
+  # every directory that is in 'base', needs to add '..'
+  while true:
+    if bb[1] >= bb[0]:
+      if result.len > 0 and result[^1] != sep:
+        result.add sep
+      result.add ".."
+    if not b.hasNext(base): break
+    bb = b.next(base)
+
+  # add the rest of 'path':
+  while true:
+    if ff[1] >= ff[0]:
+      if result.len > 0 and result[^1] != sep:
+        result.add sep
+      for i in 0..ff[1] - ff[0]:
+        result.add path[i + ff[0]]
+    if not f.hasNext(path): break
+    ff = f.next(path)
+
+  when not defined(nimOldRelativePathBehavior):
+    if result.len == 0: result.add "."
+
+proc isRelativeTo*(path: string, base: string): bool {.since: (1, 1).} =
+  ## Returns true if `path` is relative to `base`.
+  runnableExamples:
+    doAssert isRelativeTo("./foo//bar", "foo")
+    doAssert isRelativeTo("foo/bar", ".")
+    doAssert isRelativeTo("/foo/bar.nim", "/foo/bar.nim")
+    doAssert not isRelativeTo("foo/bar.nims", "foo/bar.nim")
+  let path = path.normalizePath
+  let base = base.normalizePath
+  let ret = relativePath(path, base)
+  result = path.len > 0 and not ret.startsWith ".."
+
+proc parentDirPos(path: string): int =
+  var q = 1
+  if len(path) >= 1 and path[len(path)-1] in {DirSep, AltSep}: q = 2
+  for i in countdown(len(path)-q, 0):
+    if path[i] in {DirSep, AltSep}: return i
+  result = -1
+
+proc parentDir*(path: string): string {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Returns the parent directory of `path`.
+  ##
+  ## This is similar to ``splitPath(path).head`` when ``path`` doesn't end
+  ## in a dir separator, but also takes care of path normalizations.
+  ## The remainder can be obtained with `lastPathPart(path) proc`_.
+  ##
+  ## See also:
+  ## * `relativePath proc`_
+  ## * `splitPath proc`_
+  ## * `tailDir proc`_
+  ## * `parentDirs iterator`_
+  runnableExamples:
+    assert parentDir("") == ""
+    when defined(posix):
+      assert parentDir("/usr/local/bin") == "/usr/local"
+      assert parentDir("foo/bar//") == "foo"
+      assert parentDir("//foo//bar//.") == "/foo"
+      assert parentDir("./foo") == "."
+      assert parentDir("/./foo//./") == "/"
+      assert parentDir("a//./") == "."
+      assert parentDir("a/b/c/..") == "a"
+  result = pathnorm.normalizePath(path)
+  when doslikeFileSystem:
+    let (drive, splitpath) = splitDrive(result)
+    result = splitpath
+  var sepPos = parentDirPos(result)
+  if sepPos >= 0:
+    result = substr(result, 0, sepPos)
+    normalizePathEnd(result)
+  elif result == ".." or result == "." or result.len == 0 or result[^1] in {DirSep, AltSep}:
+    # `.` => `..` and .. => `../..`(etc) would be a sensible alternative
+    # `/` => `/` (as done with splitFile) would be a sensible alternative
+    result = ""
+  else:
+    result = "."
+  when doslikeFileSystem:
+    if result.len == 0:
+      discard
+    elif drive.len > 0 and result.len == 1 and result[0] in {DirSep, AltSep}:
+      result = drive
+    else:
+      result = drive & result
+
+proc tailDir*(path: string): string {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Returns the tail part of `path`.
+  ##
+  ## See also:
+  ## * `relativePath proc`_
+  ## * `splitPath proc`_
+  ## * `parentDir proc`_
+  runnableExamples:
+    assert tailDir("/bin") == "bin"
+    assert tailDir("bin") == ""
+    assert tailDir("bin/") == ""
+    assert tailDir("/usr/local/bin") == "usr/local/bin"
+    assert tailDir("//usr//local//bin//") == "usr//local//bin//"
+    assert tailDir("./usr/local/bin") == "usr/local/bin"
+    assert tailDir("usr/local/bin") == "local/bin"
+
+  var i = 0
+  when doslikeFileSystem:
+    let (drive, splitpath) = path.splitDrive
+    if drive != "":
+      return splitpath.strip(chars = {DirSep, AltSep}, trailing = false)
+  while i < len(path):
+    if path[i] in {DirSep, AltSep}:
+      while i < len(path) and path[i] in {DirSep, AltSep}: inc i
+      return substr(path, i)
+    inc i
+  result = ""
+
+proc isRootDir*(path: string): bool {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Checks whether a given `path` is a root directory.
+  runnableExamples:
+    assert isRootDir("")
+    assert isRootDir(".")
+    assert isRootDir("/")
+    assert isRootDir("a")
+    assert not isRootDir("/a")
+    assert not isRootDir("a/b/c")
+
+  when doslikeFileSystem:
+    if splitDrive(path).path == "":
+      return true
+  result = parentDirPos(path) < 0
+
+iterator parentDirs*(path: string, fromRoot=false, inclusive=true): string =
+  ## Walks over all parent directories of a given `path`.
+  ##
+  ## If `fromRoot` is true (default: false), the traversal will start from
+  ## the file system root directory.
+  ## If `inclusive` is true (default), the original argument will be included
+  ## in the traversal.
+  ##
+  ## Relative paths won't be expanded by this iterator. Instead, it will traverse
+  ## only the directories appearing in the relative path.
+  ##
+  ## See also:
+  ## * `parentDir proc`_
+  ##
+  runnableExamples:
+    let g = "a/b/c"
+
+    for p in g.parentDirs:
+      echo p
+      # a/b/c
+      # a/b
+      # a
+
+    for p in g.parentDirs(fromRoot=true):
+      echo p
+      # a/
+      # a/b/
+      # a/b/c
+
+    for p in g.parentDirs(inclusive=false):
+      echo p
+      # a/b
+      # a
+
+  if not fromRoot:
+    var current = path
+    if inclusive: yield path
+    while true:
+      if current.isRootDir: break
+      current = current.parentDir
+      yield current
+  else:
+    when doslikeFileSystem:
+      let start = path.splitDrive.drive.len
+    else:
+      const start = 0
+    for i in countup(start, path.len - 2): # ignore the last /
+      # deal with non-normalized paths such as /foo//bar//baz
+      if path[i] in {DirSep, AltSep} and
+          (i == 0 or path[i-1] notin {DirSep, AltSep}):
+        yield path.substr(0, i)
+
+    if inclusive: yield path
+
+proc `/../`*(head, tail: string): string {.noSideEffect.} =
+  ## The same as ``parentDir(head) / tail``, unless there is no parent
+  ## directory. Then ``head / tail`` is performed instead.
+  ##
+  ## See also:
+  ## * `/ proc`_
+  ## * `parentDir proc`_
+  runnableExamples:
+    when defined(posix):
+      assert "a/b/c" /../ "d/e" == "a/b/d/e"
+      assert "a" /../ "d/e" == "a/d/e"
+
+  when doslikeFileSystem:
+    let (drive, head) = splitDrive(head)
+  let sepPos = parentDirPos(head)
+  if sepPos >= 0:
+    result = substr(head, 0, sepPos-1) / tail
+  else:
+    result = head / tail
+  when doslikeFileSystem:
+    result = drive / result
+
+proc normExt(ext: string): string =
+  if ext == "" or ext[0] == ExtSep: result = ext # no copy needed here
+  else: result = ExtSep & ext
+
+proc searchExtPos*(path: string): int =
+  ## Returns index of the `'.'` char in `path` if it signifies the beginning
+  ## of the file extension. Returns -1 otherwise.
+  ##
+  ## See also:
+  ## * `splitFile proc`_
+  ## * `extractFilename proc`_
+  ## * `lastPathPart proc`_
+  ## * `changeFileExt proc`_
+  ## * `addFileExt proc`_
+  runnableExamples:
+    assert searchExtPos("a/b/c") == -1
+    assert searchExtPos("c.nim") == 1
+    assert searchExtPos("a/b/c.nim") == 5
+    assert searchExtPos("a.b.c.nim") == 5
+    assert searchExtPos(".nim") == -1
+    assert searchExtPos("..nim") == -1
+    assert searchExtPos("a..nim") == 2
+
+  # Unless there is any char that is not `ExtSep` before last `ExtSep` in the file name,
+  # it is not a file extension.
+  const DirSeps = when doslikeFileSystem: {DirSep, AltSep, ':'} else: {DirSep, AltSep}
+  result = -1
+  var i = path.high
+  while i >= 1:
+    if path[i] == ExtSep:
+      break
+    elif path[i] in DirSeps:
+      return -1 # do not skip over path
+    dec i
+
+  for j in countdown(i - 1, 0):
+    if path[j] in DirSeps:
+      return -1
+    elif path[j] != ExtSep:
+      result = i
+      break
+
+proc splitFile*(path: string): tuple[dir, name, ext: string] {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Splits a filename into `(dir, name, extension)` tuple.
+  ##
+  ## `dir` does not end in DirSep_ unless it's `/`.
+  ## `extension` includes the leading dot.
+  ##
+  ## If `path` has no extension, `ext` is the empty string.
+  ## If `path` has no directory component, `dir` is the empty string.
+  ## If `path` has no filename component, `name` and `ext` are empty strings.
+  ##
+  ## See also:
+  ## * `searchExtPos proc`_
+  ## * `extractFilename proc`_
+  ## * `lastPathPart proc`_
+  ## * `changeFileExt proc`_
+  ## * `addFileExt proc`_
+  runnableExamples:
+    var (dir, name, ext) = splitFile("usr/local/nimc.html")
+    assert dir == "usr/local"
+    assert name == "nimc"
+    assert ext == ".html"
+    (dir, name, ext) = splitFile("/usr/local/os")
+    assert dir == "/usr/local"
+    assert name == "os"
+    assert ext == ""
+    (dir, name, ext) = splitFile("/usr/local/")
+    assert dir == "/usr/local"
+    assert name == ""
+    assert ext == ""
+    (dir, name, ext) = splitFile("/tmp.txt")
+    assert dir == "/"
+    assert name == "tmp"
+    assert ext == ".txt"
+
+  var namePos = 0
+  var dotPos = 0
+  when doslikeFileSystem:
+    let (drive, _) = splitDrive(path)
+    let stop = len(drive)
+    result.dir = drive
+  else:
+    const stop = 0
+  for i in countdown(len(path) - 1, stop):
+    if path[i] in {DirSep, AltSep} or i == 0:
+      if path[i] in {DirSep, AltSep}:
+        result.dir = substr(path, 0, if likely(i >= 1): i - 1 else: 0)
+        namePos = i + 1
+      if dotPos > i:
+        result.name = substr(path, namePos, dotPos - 1)
+        result.ext = substr(path, dotPos)
+      else:
+        result.name = substr(path, namePos)
+      break
+    elif path[i] == ExtSep and i > 0 and i < len(path) - 1 and
+         path[i - 1] notin {DirSep, AltSep} and
+         path[i + 1] != ExtSep and dotPos == 0:
+      dotPos = i
+
+proc extractFilename*(path: string): string {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Extracts the filename of a given `path`.
+  ##
+  ## This is the same as ``name & ext`` from `splitFile(path) proc`_.
+  ##
+  ## See also:
+  ## * `searchExtPos proc`_
+  ## * `splitFile proc`_
+  ## * `lastPathPart proc`_
+  ## * `changeFileExt proc`_
+  ## * `addFileExt proc`_
+  runnableExamples:
+    assert extractFilename("foo/bar/") == ""
+    assert extractFilename("foo/bar") == "bar"
+    assert extractFilename("foo/bar.baz") == "bar.baz"
+
+  if path.len == 0 or path[path.len-1] in {DirSep, AltSep}:
+    result = ""
+  else:
+    result = splitPath(path).tail
+
+proc lastPathPart*(path: string): string {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Like `extractFilename proc`_, but ignores
+  ## trailing dir separator; aka: `baseName`:idx: in some other languages.
+  ##
+  ## See also:
+  ## * `searchExtPos proc`_
+  ## * `splitFile proc`_
+  ## * `extractFilename proc`_
+  ## * `changeFileExt proc`_
+  ## * `addFileExt proc`_
+  runnableExamples:
+    assert lastPathPart("foo/bar/") == "bar"
+    assert lastPathPart("foo/bar") == "bar"
+
+  let path = path.normalizePathEnd(trailingSep = false)
+  result = extractFilename(path)
+
+proc changeFileExt*(filename, ext: string): string {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Changes the file extension to `ext`.
+  ##
+  ## If the `filename` has no extension, `ext` will be added.
+  ## If `ext` == "" then any extension is removed.
+  ##
+  ## `Ext` should be given without the leading `'.'`, because some
+  ## filesystems may use a different character. (Although I know
+  ## of none such beast.)
+  ##
+  ## See also:
+  ## * `searchExtPos proc`_
+  ## * `splitFile proc`_
+  ## * `extractFilename proc`_
+  ## * `lastPathPart proc`_
+  ## * `addFileExt proc`_
+  runnableExamples:
+    assert changeFileExt("foo.bar", "baz") == "foo.baz"
+    assert changeFileExt("foo.bar", "") == "foo"
+    assert changeFileExt("foo", "baz") == "foo.baz"
+
+  var extPos = searchExtPos(filename)
+  if extPos < 0: result = filename & normExt(ext)
+  else: result = substr(filename, 0, extPos-1) & normExt(ext)
+
+proc addFileExt*(filename, ext: string): string {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Adds the file extension `ext` to `filename`, unless
+  ## `filename` already has an extension.
+  ##
+  ## `Ext` should be given without the leading `'.'`, because some
+  ## filesystems may use a different character.
+  ## (Although I know of none such beast.)
+  ##
+  ## See also:
+  ## * `searchExtPos proc`_
+  ## * `splitFile proc`_
+  ## * `extractFilename proc`_
+  ## * `lastPathPart proc`_
+  ## * `changeFileExt proc`_
+  runnableExamples:
+    assert addFileExt("foo.bar", "baz") == "foo.bar"
+    assert addFileExt("foo.bar", "") == "foo.bar"
+    assert addFileExt("foo", "baz") == "foo.baz"
+
+  var extPos = searchExtPos(filename)
+  if extPos < 0: result = filename & normExt(ext)
+  else: result = filename
+
+proc cmpPaths*(pathA, pathB: string): int {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Compares two paths.
+  ##
+  ## On a case-sensitive filesystem this is done
+  ## case-sensitively otherwise case-insensitively. Returns:
+  ##
+  ## | `0` if pathA == pathB
+  ## | `< 0` if pathA < pathB
+  ## | `> 0` if pathA > pathB
+  runnableExamples:
+    when defined(macosx):
+      assert cmpPaths("foo", "Foo") == 0
+    elif defined(posix):
+      assert cmpPaths("foo", "Foo") > 0
+
+  let a = normalizePath(pathA)
+  let b = normalizePath(pathB)
+  if FileSystemCaseSensitive:
+    result = cmp(a, b)
+  else:
+    when defined(nimscript):
+      result = cmpic(a, b)
+    elif defined(nimdoc): discard
+    else:
+      result = cmpIgnoreCase(a, b)
+
+proc unixToNativePath*(path: string, drive=""): string {.
+  noSideEffect, rtl, extern: "nos$1".} =
+  ## Converts an UNIX-like path to a native one.
+  ##
+  ## On an UNIX system this does nothing. Else it converts
+  ## `'/'`, `'.'`, `'..'` to the appropriate things.
+  ##
+  ## On systems with a concept of "drives", `drive` is used to determine
+  ## which drive label to use during absolute path conversion.
+  ## `drive` defaults to the drive of the current working directory, and is
+  ## ignored on systems that do not have a concept of "drives".
+  when defined(unix):
+    result = path
+  else:
+    if path.len == 0: return ""
+
+    var start: int
+    if path[0] == '/':
+      # an absolute path
+      when doslikeFileSystem:
+        if drive != "":
+          result = drive & ":" & DirSep
+        else:
+          result = $DirSep
+      elif defined(macos):
+        result = "" # must not start with ':'
+      else:
+        result = $DirSep
+      start = 1
+    elif path[0] == '.' and (path.len == 1 or path[1] == '/'):
+      # current directory
+      result = $CurDir
+      start = when doslikeFileSystem: 1 else: 2
+    else:
+      result = ""
+      start = 0
+
+    var i = start
+    while i < len(path): # ../../../ --> ::::
+      if i+2 < path.len and path[i] == '.' and path[i+1] == '.' and path[i+2] == '/':
+        # parent directory
+        when defined(macos):
+          if result[high(result)] == ':':
+            add result, ':'
+          else:
+            add result, ParDir
+        else:
+          add result, ParDir & DirSep
+        inc(i, 3)
+      elif path[i] == '/':
+        add result, DirSep
+        inc(i)
+      else:
+        add result, path[i]
+        inc(i)
+
+
+when not defined(nimscript):
+  proc getCurrentDir*(): string {.rtl, extern: "nos$1", tags: [].} =
+    ## Returns the `current working directory`:idx: i.e. where the built
+    ## binary is run.
+    ##
+    ## So the path returned by this proc is determined at run time.
+    ##
+    ## See also:
+    ## * `getHomeDir proc`_
+    ## * `getConfigDir proc`_
+    ## * `getTempDir proc`_
+    ## * `setCurrentDir proc`_
+    ## * `currentSourcePath template <system.html#currentSourcePath.t>`_
+    ## * `getProjectPath proc <macros.html#getProjectPath>`_
+    when defined(nodejs):
+      var ret: cstring
+      {.emit: "`ret` = process.cwd();".}
+      return $ret
+    elif defined(js):
+      raiseAssert "use -d:nodejs to have `getCurrentDir` defined"
+    elif defined(windows):
+      var bufsize = MAX_PATH.int32
+      var res = newWideCString(bufsize)
+      while true:
+        var L = getCurrentDirectoryW(bufsize, res)
+        if L == 0'i32:
+          raiseOSError(osLastError())
+        elif L > bufsize:
+          res = newWideCString(L)
+          bufsize = L
+        else:
+          result = res$L
+          break
+    else:
+      var bufsize = 1024 # should be enough
+      result = newString(bufsize)
+      while true:
+        if getcwd(result.cstring, bufsize) != nil:
+          setLen(result, c_strlen(result.cstring))
+          break
+        else:
+          let err = osLastError()
+          if err.int32 == ERANGE:
+            bufsize = bufsize shl 1
+            doAssert(bufsize >= 0)
+            result = newString(bufsize)
+          else:
+            raiseOSError(osLastError())
+
+proc absolutePath*(path: string, root = getCurrentDir()): string =
+  ## Returns the absolute path of `path`, rooted at `root` (which must be absolute;
+  ## default: current directory).
+  ## If `path` is absolute, return it, ignoring `root`.
+  ##
+  ## See also:
+  ## * `normalizedPath proc`_
+  ## * `normalizePath proc`_
+  runnableExamples:
+    assert absolutePath("a") == getCurrentDir() / "a"
+
+  if isAbsolute(path): path
+  else:
+    if not root.isAbsolute:
+      raise newException(ValueError, "The specified root is not absolute: " & root)
+    joinPath(root, path)
+
+proc absolutePathInternal(path: string): string =
+  absolutePath(path, getCurrentDir())
+
+
+proc normalizePath*(path: var string) {.rtl, extern: "nos$1", tags: [].} =
+  ## Normalize a path.
+  ##
+  ## Consecutive directory separators are collapsed, including an initial double slash.
+  ##
+  ## On relative paths, double dot (`..`) sequences are collapsed if possible.
+  ## On absolute paths they are always collapsed.
+  ##
+  ## .. warning:: URL-encoded and Unicode attempts at directory traversal are not detected.
+  ##   Triple dot is not handled.
+  ##
+  ## See also:
+  ## * `absolutePath proc`_
+  ## * `normalizedPath proc`_ for outplace version
+  ## * `normalizeExe proc`_
+  runnableExamples:
+    when defined(posix):
+      var a = "a///b//..//c///d"
+      a.normalizePath()
+      assert a == "a/c/d"
+
+  path = pathnorm.normalizePath(path)
+  when false:
+    let isAbs = isAbsolute(path)
+    var stack: seq[string] = @[]
+    for p in split(path, {DirSep}):
+      case p
+      of "", ".":
+        continue
+      of "..":
+        if stack.len == 0:
+          if isAbs:
+            discard  # collapse all double dots on absoluta paths
+          else:
+            stack.add(p)
+        elif stack[^1] == "..":
+          stack.add(p)
+        else:
+          discard stack.pop()
+      else:
+        stack.add(p)
+
+    if isAbs:
+      path = DirSep & join(stack, $DirSep)
+    elif stack.len > 0:
+      path = join(stack, $DirSep)
+    else:
+      path = "."
+
+proc normalizePathAux(path: var string) = normalizePath(path)
+
+proc normalizedPath*(path: string): string {.rtl, extern: "nos$1", tags: [].} =
+  ## Returns a normalized path for the current OS.
+  ##
+  ## See also:
+  ## * `absolutePath proc`_
+  ## * `normalizePath proc`_ for the in-place version
+  runnableExamples:
+    when defined(posix):
+      assert normalizedPath("a///b//..//c///d") == "a/c/d"
+  result = pathnorm.normalizePath(path)
+
+proc normalizeExe*(file: var string) {.since: (1, 3, 5).} =
+  ## on posix, prepends `./` if `file` doesn't contain `/` and is not `"", ".", ".."`.
+  runnableExamples:
+    import std/sugar
+    when defined(posix):
+      doAssert "foo".dup(normalizeExe) == "./foo"
+      doAssert "foo/../bar".dup(normalizeExe) == "foo/../bar"
+    doAssert "".dup(normalizeExe) == ""
+  when defined(posix):
+    if file.len > 0 and DirSep notin file and file != "." and file != "..":
+      file = "./" & file
+
+proc sameFile*(path1, path2: string): bool {.rtl, extern: "nos$1",
+  tags: [ReadDirEffect], noWeirdTarget.} =
+  ## Returns true if both pathname arguments refer to the same physical
+  ## file or directory.
+  ##
+  ## Raises `OSError` if any of the files does not
+  ## exist or information about it can not be obtained.
+  ##
+  ## This proc will return true if given two alternative hard-linked or
+  ## sym-linked paths to the same file or directory.
+  ##
+  ## See also:
+  ## * `sameFileContent proc`_
+  when defined(windows):
+    var success = true
+    var f1 = openHandle(path1)
+    var f2 = openHandle(path2)
+
+    var lastErr: OSErrorCode
+    if f1 != INVALID_HANDLE_VALUE and f2 != INVALID_HANDLE_VALUE:
+      var fi1, fi2: BY_HANDLE_FILE_INFORMATION
+
+      if getFileInformationByHandle(f1, addr(fi1)) != 0 and
+         getFileInformationByHandle(f2, addr(fi2)) != 0:
+        result = fi1.dwVolumeSerialNumber == fi2.dwVolumeSerialNumber and
+                 fi1.nFileIndexHigh == fi2.nFileIndexHigh and
+                 fi1.nFileIndexLow == fi2.nFileIndexLow
+      else:
+        lastErr = osLastError()
+        success = false
+    else:
+      lastErr = osLastError()
+      success = false
+
+    discard closeHandle(f1)
+    discard closeHandle(f2)
+
+    if not success: raiseOSError(lastErr, $(path1, path2))
+  else:
+    var a, b: Stat
+    if stat(path1, a) < 0'i32 or stat(path2, b) < 0'i32:
+      raiseOSError(osLastError(), $(path1, path2))
+    else:
+      result = a.st_dev == b.st_dev and a.st_ino == b.st_ino
diff --git a/lib/std/private/osseps.nim b/lib/std/private/osseps.nim
new file mode 100644
index 000000000..f2d49d886
--- /dev/null
+++ b/lib/std/private/osseps.nim
@@ -0,0 +1,113 @@
+# Include file that implements 'DirSep' and friends. Do not import this when
+# you also import `os.nim`!
+
+# Improved based on info in 'compiler/platform.nim'
+
+## .. importdoc:: ospaths2.nim
+
+const
+  doslikeFileSystem* = defined(windows) or defined(OS2) or defined(DOS)
+
+const
+  CurDir* =
+    when defined(macos): ':'
+    elif defined(genode): '/'
+    else: '.'
+    ## The constant character used by the operating system to refer to the
+    ## current directory.
+    ##
+    ## For example: `'.'` for POSIX or `':'` for the classic Macintosh.
+
+  ParDir* =
+    when defined(macos): "::"
+    else: ".."
+    ## The constant string used by the operating system to refer to the
+    ## parent directory.
+    ##
+    ## For example: `".."` for POSIX or `"::"` for the classic Macintosh.
+
+  DirSep* =
+    when defined(macos): ':'
+    elif doslikeFileSystem or defined(vxworks): '\\'
+    elif defined(RISCOS): '.'
+    else: '/'
+    ## The character used by the operating system to separate pathname
+    ## components, for example: `'/'` for POSIX, `':'` for the classic
+    ## Macintosh, and `'\\'` on Windows.
+
+  AltSep* =
+    when doslikeFileSystem: '/'
+    else: DirSep
+    ## An alternative character used by the operating system to separate
+    ## pathname components, or the same as DirSep_ if only one separator
+    ## character exists. This is set to `'/'` on Windows systems
+    ## where DirSep_ is a backslash (`'\\'`).
+
+  PathSep* =
+    when defined(macos) or defined(RISCOS): ','
+    elif doslikeFileSystem or defined(vxworks): ';'
+    elif defined(PalmOS) or defined(MorphOS): ':' # platform has ':' but osseps has ';'
+    else: ':'
+    ## The character conventionally used by the operating system to separate
+    ## search path components (as in PATH), such as `':'` for POSIX
+    ## or `';'` for Windows.
+
+  FileSystemCaseSensitive* =
+    when defined(macos) or defined(macosx) or doslikeFileSystem or defined(vxworks) or
+         defined(PalmOS) or defined(MorphOS): false
+    else: true
+    ## True if the file system is case sensitive, false otherwise. Used by
+    ## `cmpPaths proc`_ to compare filenames properly.
+
+  ExeExt* =
+    when doslikeFileSystem: "exe"
+    elif defined(atari): "tpp"
+    elif defined(netware): "nlm"
+    elif defined(vxworks): "vxe"
+    elif defined(nintendoswitch): "elf"
+    else: ""
+    ## The file extension of native executables. For example:
+    ## `""` for POSIX, `"exe"` on Windows (without a dot).
+
+  ScriptExt* =
+    when doslikeFileSystem: "bat"
+    else: ""
+    ## The file extension of a script file. For example: `""` for POSIX,
+    ## `"bat"` on Windows.
+
+  DynlibFormat* =
+    when defined(macos): "$1.dylib" # platform has $1Lib
+    elif defined(macosx): "lib$1.dylib"
+    elif doslikeFileSystem or defined(atari): "$1.dll"
+    elif defined(MorphOS): "$1.prc"
+    elif defined(PalmOS): "$1.prc" # platform has lib$1.so
+    elif defined(genode): "$1.lib.so"
+    elif defined(netware): "$1.nlm"
+    elif defined(amiga): "$1.Library"
+    else: "lib$1.so"
+    ## The format string to turn a filename into a `DLL`:idx: file (also
+    ## called `shared object`:idx: on some operating systems).
+
+  ExtSep* = '.'
+    ## The character which separates the base filename from the extension;
+    ## for example, the `'.'` in `os.nim`.
+
+  #  MacOS paths
+  #  ===========
+  #  MacOS directory separator is a colon ":" which is the only character not
+  #  allowed in filenames.
+  #
+  #  A path containing no colon or which begins with a colon is a partial
+  #  path.
+  #  E.g. ":kalle:petter" ":kalle" "kalle"
+  #
+  #  All other paths are full (absolute) paths. E.g. "HD:kalle:" "HD:"
+  #  When generating paths, one is safe if one ensures that all partial paths
+  #  begin with a colon, and all full paths end with a colon.
+  #  In full paths the first name (e g HD above) is the name of a mounted
+  #  volume.
+  #  These names are not unique, because, for instance, two diskettes with the
+  #  same names could be inserted. This means that paths on MacOS are not
+  #  waterproof. In case of equal names the first volume found will do.
+  #  Two colons "::" are the relative path to the parent. Three is to the
+  #  grandparent etc.
diff --git a/lib/std/private/ossymlinks.nim b/lib/std/private/ossymlinks.nim
new file mode 100644
index 000000000..c1760c42e
--- /dev/null
+++ b/lib/std/private/ossymlinks.nim
@@ -0,0 +1,78 @@
+include system/inclrtl
+import std/oserrors
+
+import oscommon
+export symlinkExists
+
+when defined(nimPreviewSlimSystem):
+  import std/[syncio, assertions, widestrs]
+
+when weirdTarget:
+  discard
+elif defined(windows):
+  import std/[winlean, times]
+elif defined(posix):
+  import std/posix
+else:
+  {.error: "OS module not ported to your operating system!".}
+
+
+when weirdTarget:
+  {.pragma: noWeirdTarget, error: "this proc is not available on the NimScript/js target".}
+else:
+  {.pragma: noWeirdTarget.}
+
+
+when defined(nimscript):
+  # for procs already defined in scriptconfig.nim
+  template noNimJs(body): untyped = discard
+elif defined(js):
+  {.pragma: noNimJs, error: "this proc is not available on the js target".}
+else:
+  {.pragma: noNimJs.}
+
+## .. importdoc:: os.nim
+
+proc createSymlink*(src, dest: string) {.noWeirdTarget.} =
+  ## Create a symbolic link at `dest` which points to the item specified
+  ## by `src`. On most operating systems, will fail if a link already exists.
+  ##
+  ## .. warning:: Some OS's (such as Microsoft Windows) restrict the creation
+  ##   of symlinks to root users (administrators) or users with developer mode enabled.
+  ##
+  ## See also:
+  ## * `createHardlink proc`_
+  ## * `expandSymlink proc`_
+
+  when defined(windows):
+    const SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE = 2
+    # allows anyone with developer mode on to create a link
+    let flag = dirExists(src).int32 or SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
+    var wSrc = newWideCString(src)
+    var wDst = newWideCString(dest)
+    if createSymbolicLinkW(wDst, wSrc, flag) == 0 or getLastError() != 0:
+      raiseOSError(osLastError(), $(src, dest))
+  else:
+    if symlink(src, dest) != 0:
+      raiseOSError(osLastError(), $(src, dest))
+
+proc expandSymlink*(symlinkPath: string): string {.noWeirdTarget.} =
+  ## Returns a string representing the path to which the symbolic link points.
+  ##
+  ## On Windows this is a noop, `symlinkPath` is simply returned.
+  ##
+  ## See also:
+  ## * `createSymlink proc`_
+  when defined(windows) or defined(nintendoswitch):
+    result = symlinkPath
+  else:
+    var bufLen = 1024
+    while true:
+      result = newString(bufLen)
+      let len = readlink(symlinkPath.cstring, result.cstring, bufLen)
+      if len < 0:
+        raiseOSError(osLastError(), symlinkPath)
+      if len < bufLen:
+        result.setLen(len)
+        break
+      bufLen = bufLen shl 1
diff --git a/lib/std/private/schubfach.nim b/lib/std/private/schubfach.nim
index 872317ebf..b8c85d2bc 100644
--- a/lib/std/private/schubfach.nim
+++ b/lib/std/private/schubfach.nim
@@ -39,10 +39,10 @@ const
   exponentMask: BitsType = maxIeeeExponent shl (significandSize - 1)
   signMask: BitsType = not (not BitsType(0) shr 1)
 
-proc constructSingle(bits: BitsType): Single {.constructor.} =
+proc constructSingle(bits: BitsType): Single  =
   result.bits = bits
 
-proc constructSingle(value: ValueType): Single {.constructor.} =
+proc constructSingle(value: ValueType): Single  =
   result.bits = cast[typeof(result.bits)](value)
 
 proc physicalSignificand(this: Single): BitsType {.noSideEffect.} =
@@ -244,12 +244,12 @@ proc toDecimal32(ieeeSignificand: uint32; ieeeExponent: uint32): FloatingDecimal
 ##  ToChars
 ## ==================================================================================================
 
-proc printDecimalDigitsBackwards(buf: var openArray[char]; pos: int; output: uint32): int32 {.inline.} =
+proc printDecimalDigitsBackwards[T: Ordinal](buf: var openArray[char]; pos: T; output: uint32): int {.inline.} =
   var output = output
   var pos = pos
-  var tz: int32 = 0
+  var tz = 0
   ##  number of trailing zeros removed.
-  var nd: int32 = 0
+  var nd = 0
   ##  number of decimal digits processed.
   ##  At most 9 digits remaining
   if output >= 10000:
@@ -300,7 +300,7 @@ proc printDecimalDigitsBackwards(buf: var openArray[char]; pos: int; output: uin
     buf[pos] = chr(uint32('0') + q)
   return tz
 
-proc decimalLength(v: uint32): int32 {.inline.} =
+proc decimalLength(v: uint32): int {.inline.} =
   sf_Assert(v >= 1)
   sf_Assert(v <= 999999999'u)
   if v >= 100000000'u:
@@ -321,7 +321,7 @@ proc decimalLength(v: uint32): int32 {.inline.} =
     return 2
   return 1
 
-proc formatDigits(buffer: var openArray[char]; pos: int; digits: uint32; decimalExponent: int32;
+proc formatDigits[T: Ordinal](buffer: var openArray[char]; pos: T; digits: uint32; decimalExponent: int;
                   forceTrailingDotZero: bool = false): int {.inline.} =
   const
     minFixedDecimalPoint: int32 = -4
@@ -333,8 +333,8 @@ proc formatDigits(buffer: var openArray[char]; pos: int; digits: uint32; decimal
   sf_Assert(digits <= 999999999'u)
   sf_Assert(decimalExponent >= -99)
   sf_Assert(decimalExponent <= 99)
-  var numDigits: int32 = decimalLength(digits)
-  let decimalPoint: int32 = numDigits + decimalExponent
+  var numDigits = decimalLength(digits)
+  let decimalPoint = numDigits + decimalExponent
   let useFixed: bool = minFixedDecimalPoint <= decimalPoint and
       decimalPoint <= maxFixedDecimalPoint
   ##  Prepare the buffer.
@@ -342,7 +342,7 @@ proc formatDigits(buffer: var openArray[char]; pos: int; digits: uint32; decimal
   for i in 0..<32: buffer[pos+i] = '0'
   assert(minFixedDecimalPoint >= -30, "internal error")
   assert(maxFixedDecimalPoint <= 32, "internal error")
-  var decimalDigitsPosition: int32
+  var decimalDigitsPosition: int
   if useFixed:
     if decimalPoint <= 0:
       ##  0.[000]digits
@@ -355,7 +355,7 @@ proc formatDigits(buffer: var openArray[char]; pos: int; digits: uint32; decimal
     ##  dE+123 or d.igitsE+123
     decimalDigitsPosition = 1
   var digitsEnd = pos + decimalDigitsPosition + numDigits
-  let tz: int32 = printDecimalDigitsBackwards(buffer, digitsEnd, digits)
+  let tz = printDecimalDigitsBackwards(buffer, digitsEnd, digits)
   dec(digitsEnd, tz)
   dec(numDigits, tz)
   ##   decimal_exponent += tz; // => decimal_point unchanged.
@@ -386,7 +386,7 @@ proc formatDigits(buffer: var openArray[char]; pos: int; digits: uint32; decimal
       ##  d.igitsE+123
       buffer[pos+1] = '.'
       pos = digitsEnd
-    let scientificExponent: int32 = decimalPoint - 1
+    let scientificExponent = decimalPoint - 1
     ##       SF_ASSERT(scientific_exponent != 0);
     buffer[pos] = 'e'
     buffer[pos+1] = if scientificExponent < 0: '-' else: '+'
@@ -412,7 +412,7 @@ proc float32ToChars*(buffer: var openArray[char]; v: float32; forceTrailingDotZe
     if exponent != 0 or significand != 0:
       ##  != 0
       let dec: auto = toDecimal32(significand, exponent)
-      return formatDigits(buffer, pos, dec.digits, dec.exponent, forceTrailingDotZero)
+      return formatDigits(buffer, pos, dec.digits, dec.exponent.int, forceTrailingDotZero)
     else:
       buffer[pos] = '0'
       buffer[pos+1] = '.'
diff --git a/lib/std/private/since.nim b/lib/std/private/since.nim
index 5b22b6391..720120f11 100644
--- a/lib/std/private/since.nim
+++ b/lib/std/private/since.nim
@@ -1,5 +1,5 @@
 ##[
-`since` is used to emulate older versions of nim stdlib with `--useVersion`,
+`since` is used to emulate older versions of nim stdlib,
 see `tuse_version.nim`.
 
 If a symbol `foo` is added in version `(1,3,5)`, use `{.since: (1.3.5).}`, not
@@ -15,19 +15,19 @@ The emulation cannot be 100% faithful and to avoid adding too much complexity,
 template since*(version: (int, int), body: untyped) {.dirty.} =
   ## Evaluates `body` if the ``(NimMajor, NimMinor)`` is greater than
   ## or equal to `version`. Usage:
-  ##
-  ## .. code-block:: Nim
+  ##   ```Nim
   ##   proc fun*() {.since: (1, 3).}
   ##   since (1, 3): fun()
+  ##   ```
   when (NimMajor, NimMinor) >= version:
     body
 
 template since*(version: (int, int, int), body: untyped) {.dirty.} =
   ## Evaluates `body` if ``(NimMajor, NimMinor, NimPatch)`` is greater than 
   ## or equal to `version`. Usage:
-  ##
-  ## .. code-block:: Nim
+  ##   ```Nim
   ##   proc fun*() {.since: (1, 3, 1).}
   ##   since (1, 3, 1): fun()
+  ##   ```
   when (NimMajor, NimMinor, NimPatch) >= version:
     body
diff --git a/lib/std/private/strimpl.nim b/lib/std/private/strimpl.nim
index 7d42a7cf8..f8c9236a5 100644
--- a/lib/std/private/strimpl.nim
+++ b/lib/std/private/strimpl.nim
@@ -74,3 +74,40 @@ template endsWithImpl*[T: string | cstring](s, suffix: T) =
 
 func cmpNimIdentifier*[T: string | cstring](a, b: T): int =
   cmpIgnoreStyleImpl(a, b, true)
+
+func c_memchr(cstr: pointer, c: char, n: csize_t): pointer {.
+              importc: "memchr", header: "<string.h>".}
+func c_strstr(haystack, needle: cstring): cstring {.
+  importc: "strstr", header: "<string.h>".}
+
+
+func find*(s: cstring, sub: char, start: Natural = 0, last = 0): int =
+  ## Searches for `sub` in `s` inside the range `start..last` (both ends included).
+  ## If `last` is unspecified, it defaults to `s.high` (the last element).
+  ##
+  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
+  ## Otherwise the index returned is relative to `s[0]`, not `start`.
+  ## Use `s[start..last].rfind` for a `start`-origin index.
+  let last = if last == 0: s.high else: last
+  let L = last-start+1
+  if L > 0:
+    let found = c_memchr(s[start].unsafeAddr, sub, cast[csize_t](L))
+    if not found.isNil:
+      return cast[int](found) -% cast[int](s)
+  return -1
+
+func find*(s, sub: cstring, start: Natural = 0, last = 0): int =
+  ## Searches for `sub` in `s` inside the range `start..last` (both ends included).
+  ## If `last` is unspecified, it defaults to `s.high` (the last element).
+  ##
+  ## Searching is case-sensitive. If `sub` is not in `s`, -1 is returned.
+  ## Otherwise the index returned is relative to `s[0]`, not `start`.
+  ## Use `s[start..last].find` for a `start`-origin index.
+  if sub.len > s.len - start: return -1
+  if sub.len == 1: return find(s, sub[0], start, last)
+  if last == 0 and s.len > start:
+    let found = c_strstr(cast[cstring](s[start].unsafeAddr), sub)
+    if not found.isNil:
+      result = cast[int](found) -% cast[int](s)
+    else:
+      result = -1
diff --git a/lib/std/private/syslocks.nim b/lib/std/private/syslocks.nim
new file mode 100644
index 000000000..e19ec2c04
--- /dev/null
+++ b/lib/std/private/syslocks.nim
@@ -0,0 +1,234 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2012 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+# Low level system locks and condition vars.
+
+{.push stackTrace: off.}
+
+when defined(windows):
+  type
+    Handle = int
+
+    SysLock* {.importc: "CRITICAL_SECTION",
+              header: "<windows.h>", final, pure, byref.} = object # CRITICAL_SECTION in WinApi
+      DebugInfo: pointer
+      LockCount: int32
+      RecursionCount: int32
+      OwningThread: int
+      LockSemaphore: int
+      SpinCount: int
+
+    SysCond* {.importc: "RTL_CONDITION_VARIABLE", header: "<windows.h>", byref.} = object
+      thePtr {.importc: "Ptr".} : Handle
+
+  proc initSysLock*(L: var SysLock) {.importc: "InitializeCriticalSection",
+                                     header: "<windows.h>".}
+    ## Initializes the lock `L`.
+
+  proc tryAcquireSysAux(L: var SysLock): int32 {.importc: "TryEnterCriticalSection",
+                                                 header: "<windows.h>".}
+    ## Tries to acquire the lock `L`.
+
+  proc tryAcquireSys*(L: var SysLock): bool {.inline.} =
+    result = tryAcquireSysAux(L) != 0'i32
+
+  proc acquireSys*(L: var SysLock) {.importc: "EnterCriticalSection",
+                                    header: "<windows.h>".}
+    ## Acquires the lock `L`.
+
+  proc releaseSys*(L: var SysLock) {.importc: "LeaveCriticalSection",
+                                    header: "<windows.h>".}
+    ## Releases the lock `L`.
+
+  proc deinitSys*(L: SysLock) {.importc: "DeleteCriticalSection",
+                                   header: "<windows.h>".}
+
+  proc initializeConditionVariable(
+    conditionVariable: var SysCond
+  ) {.stdcall, noSideEffect, dynlib: "kernel32", importc: "InitializeConditionVariable".}
+
+  proc sleepConditionVariableCS(
+    conditionVariable: var SysCond,
+    PCRITICAL_SECTION: var SysLock,
+    dwMilliseconds: int
+  ): int32 {.stdcall, noSideEffect, dynlib: "kernel32", importc: "SleepConditionVariableCS".}
+
+
+  proc signalSysCond*(hEvent: var SysCond) {.stdcall, noSideEffect,
+    dynlib: "kernel32", importc: "WakeConditionVariable".}
+
+  proc broadcastSysCond*(hEvent: var SysCond) {.stdcall, noSideEffect,
+    dynlib: "kernel32", importc: "WakeAllConditionVariable".}
+
+  proc initSysCond*(cond: var SysCond) {.inline.} =
+    initializeConditionVariable(cond)
+  proc deinitSysCond*(cond: SysCond) {.inline.} =
+    discard
+  proc waitSysCond*(cond: var SysCond, lock: var SysLock) =
+    discard sleepConditionVariableCS(cond, lock, -1'i32)
+
+elif defined(genode):
+  const
+    Header = "genode_cpp/syslocks.h"
+  type
+    SysLock* {.importcpp: "Nim::SysLock", pure, final,
+              header: Header.} = object
+    SysCond* {.importcpp: "Nim::SysCond", pure, final,
+              header: Header.} = object
+
+  proc initSysLock*(L: var SysLock) = discard
+  proc deinitSys*(L: SysLock) = discard
+  proc acquireSys*(L: var SysLock) {.noSideEffect, importcpp.}
+  proc tryAcquireSys*(L: var SysLock): bool {.noSideEffect, importcpp.}
+  proc releaseSys*(L: var SysLock) {.noSideEffect, importcpp.}
+
+  proc initSysCond*(L: var SysCond) = discard
+  proc deinitSysCond*(L: SysCond) = discard
+  proc waitSysCond*(cond: var SysCond, lock: var SysLock) {.
+    noSideEffect, importcpp.}
+  proc signalSysCond*(cond: var SysCond) {.
+    noSideEffect, importcpp.}
+  proc broadcastSysCond*(cond: var SysCond) {.
+    noSideEffect, importcpp.}
+
+else:
+  type
+    SysLockObj {.importc: "pthread_mutex_t", pure, final,
+               header: """#include <sys/types.h>
+                          #include <pthread.h>""", byref.} = object
+      when defined(linux) and defined(amd64):
+        abi: array[40 div sizeof(clong), clong]
+
+    SysLockAttr* {.importc: "pthread_mutexattr_t", pure, final
+               header: """#include <sys/types.h>
+                          #include <pthread.h>""".} = object
+      when defined(linux) and defined(amd64):
+        abi: array[4 div sizeof(cint), cint]  # actually a cint
+
+    SysCondObj {.importc: "pthread_cond_t", pure, final,
+               header: """#include <sys/types.h>
+                          #include <pthread.h>""", byref.} = object
+      when defined(linux) and defined(amd64):
+        abi: array[48 div sizeof(clonglong), clonglong]
+
+    SysCondAttr {.importc: "pthread_condattr_t", pure, final
+               header: """#include <sys/types.h>
+                          #include <pthread.h>""".} = object
+      when defined(linux) and defined(amd64):
+        abi: array[4 div sizeof(cint), cint]  # actually a cint
+
+    SysLockType = distinct cint
+
+  proc initSysLockAux(L: var SysLockObj, attr: ptr SysLockAttr) {.
+    importc: "pthread_mutex_init", header: "<pthread.h>", noSideEffect.}
+  proc deinitSysAux(L: SysLockObj) {.noSideEffect,
+    importc: "pthread_mutex_destroy", header: "<pthread.h>".}
+
+  proc acquireSysAux(L: var SysLockObj) {.noSideEffect,
+    importc: "pthread_mutex_lock", header: "<pthread.h>".}
+  proc tryAcquireSysAux(L: var SysLockObj): cint {.noSideEffect,
+    importc: "pthread_mutex_trylock", header: "<pthread.h>".}
+
+  proc releaseSysAux(L: var SysLockObj) {.noSideEffect,
+    importc: "pthread_mutex_unlock", header: "<pthread.h>".}
+
+  when defined(ios):
+    # iOS will behave badly if sync primitives are moved in memory. In order
+    # to prevent this once and for all, we're doing an extra malloc when
+    # initializing the primitive.
+    type
+      SysLock* = ptr SysLockObj
+      SysCond* = ptr SysCondObj
+
+    when not declared(c_malloc):
+      proc c_malloc(size: csize_t): pointer {.
+        importc: "malloc", header: "<stdlib.h>".}
+      proc c_free(p: pointer) {.
+        importc: "free", header: "<stdlib.h>".}
+
+    proc initSysLock*(L: var SysLock, attr: ptr SysLockAttr = nil) =
+      L = cast[SysLock](c_malloc(csize_t(sizeof(SysLockObj))))
+      initSysLockAux(L[], attr)
+
+    proc deinitSys*(L: SysLock) =
+      deinitSysAux(L[])
+      c_free(L)
+
+    template acquireSys*(L: var SysLock) =
+      acquireSysAux(L[])
+    template tryAcquireSys*(L: var SysLock): bool =
+      tryAcquireSysAux(L[]) == 0'i32
+    template releaseSys*(L: var SysLock) =
+      releaseSysAux(L[])
+  else:
+    type
+      SysLock* = SysLockObj
+      SysCond* = SysCondObj
+
+    template initSysLock*(L: var SysLock, attr: ptr SysLockAttr = nil) =
+      initSysLockAux(L, attr)
+    template deinitSys*(L: SysLock) =
+      deinitSysAux(L)
+    template acquireSys*(L: var SysLock) =
+      acquireSysAux(L)
+    template tryAcquireSys*(L: var SysLock): bool =
+      tryAcquireSysAux(L) == 0'i32
+    template releaseSys*(L: var SysLock) =
+      releaseSysAux(L)
+
+  # rlocks
+  var SysLockType_Reentrant* {.importc: "PTHREAD_MUTEX_RECURSIVE",
+    header: "<pthread.h>".}: SysLockType
+  proc initSysLockAttr*(a: var SysLockAttr) {.
+    importc: "pthread_mutexattr_init", header: "<pthread.h>", noSideEffect.}
+  proc setSysLockType*(a: var SysLockAttr, t: SysLockType) {.
+    importc: "pthread_mutexattr_settype", header: "<pthread.h>", noSideEffect.}
+
+  # locks
+  proc initSysCondAux(cond: var SysCondObj, cond_attr: ptr SysCondAttr = nil) {.
+    importc: "pthread_cond_init", header: "<pthread.h>", noSideEffect.}
+  proc deinitSysCondAux(cond: SysCondObj) {.noSideEffect,
+    importc: "pthread_cond_destroy", header: "<pthread.h>".}
+
+  proc waitSysCondAux(cond: var SysCondObj, lock: var SysLockObj): cint {.
+    importc: "pthread_cond_wait", header: "<pthread.h>", noSideEffect.}
+  proc signalSysCondAux(cond: var SysCondObj) {.
+    importc: "pthread_cond_signal", header: "<pthread.h>", noSideEffect.}
+  proc broadcastSysCondAux(cond: var SysCondObj) {.
+    importc: "pthread_cond_broadcast", header: "<pthread.h>", noSideEffect.}
+
+  when defined(ios):
+    proc initSysCond*(cond: var SysCond, cond_attr: ptr SysCondAttr = nil) =
+      cond = cast[SysCond](c_malloc(csize_t(sizeof(SysCondObj))))
+      initSysCondAux(cond[], cond_attr)
+
+    proc deinitSysCond*(cond: SysCond) =
+      deinitSysCondAux(cond[])
+      c_free(cond)
+
+    template waitSysCond*(cond: var SysCond, lock: var SysLock) =
+      discard waitSysCondAux(cond[], lock[])
+    template signalSysCond*(cond: var SysCond) =
+      signalSysCondAux(cond[])
+    template broadcastSysCond*(cond: var SysCond) =
+      broadcastSysCondAux(cond[])
+  else:
+    template initSysCond*(cond: var SysCond, cond_attr: ptr SysCondAttr = nil) =
+      initSysCondAux(cond, cond_attr)
+    template deinitSysCond*(cond: SysCond) =
+      deinitSysCondAux(cond)
+
+    template waitSysCond*(cond: var SysCond, lock: var SysLock) =
+      discard waitSysCondAux(cond, lock)
+    template signalSysCond*(cond: var SysCond) =
+      signalSysCondAux(cond)
+    template broadcastSysCond*(cond: var SysCond) =
+      broadcastSysCondAux(cond)
+
+{.pop.}
diff --git a/lib/std/private/threadtypes.nim b/lib/std/private/threadtypes.nim
new file mode 100644
index 000000000..a1cdf21dc
--- /dev/null
+++ b/lib/std/private/threadtypes.nim
@@ -0,0 +1,176 @@
+include system/inclrtl
+
+const hasSharedHeap* = defined(boehmgc) or defined(gogc) # don't share heaps; every thread has its own
+
+when defined(windows):
+  type
+    Handle* = int
+    SysThread* = Handle
+    WinThreadProc* = proc (x: pointer): int32 {.stdcall.}
+
+  proc createThread*(lpThreadAttributes: pointer, dwStackSize: int32,
+                     lpStartAddress: WinThreadProc,
+                     lpParameter: pointer,
+                     dwCreationFlags: int32,
+                     lpThreadId: var int32): SysThread {.
+    stdcall, dynlib: "kernel32", importc: "CreateThread".}
+
+  proc winSuspendThread*(hThread: SysThread): int32 {.
+    stdcall, dynlib: "kernel32", importc: "SuspendThread".}
+
+  proc winResumeThread*(hThread: SysThread): int32 {.
+    stdcall, dynlib: "kernel32", importc: "ResumeThread".}
+
+  proc waitForSingleObject*(hHandle: SysThread, dwMilliseconds: int32): int32 {.
+    stdcall, dynlib: "kernel32", importc: "WaitForSingleObject".}
+
+  proc waitForMultipleObjects*(nCount: int32,
+                              lpHandles: ptr SysThread,
+                              bWaitAll: int32,
+                              dwMilliseconds: int32): int32 {.
+    stdcall, dynlib: "kernel32", importc: "WaitForMultipleObjects".}
+
+  proc terminateThread*(hThread: SysThread, dwExitCode: int32): int32 {.
+    stdcall, dynlib: "kernel32", importc: "TerminateThread".}
+
+  proc setThreadAffinityMask*(hThread: SysThread, dwThreadAffinityMask: uint) {.
+    importc: "SetThreadAffinityMask", stdcall, header: "<windows.h>".}
+
+elif defined(genode):
+  const
+    GenodeHeader* = "genode_cpp/threads.h"
+  type
+    SysThread* {.importcpp: "Nim::SysThread",
+                 header: GenodeHeader, final, pure.} = object
+    GenodeThreadProc* = proc (x: pointer) {.noconv.}
+
+  proc initThread*(s: var SysThread,
+                  env: GenodeEnv,
+                  stackSize: culonglong,
+                  entry: GenodeThreadProc,
+                  arg: pointer,
+                  affinity: cuint) {.
+    importcpp: "#.initThread(@)".}
+
+
+else:
+  when not (defined(macosx) or defined(haiku)):
+    {.passl: "-pthread".}
+
+  when not defined(haiku):
+    {.passc: "-pthread".}
+
+  const
+    schedh = "#define _GNU_SOURCE\n#include <sched.h>"
+    pthreadh* = "#define _GNU_SOURCE\n#include <pthread.h>"
+
+  when not declared(Time):
+    when defined(linux):
+      type Time = clong
+    else:
+      type Time = int
+
+  when (defined(linux) or defined(nintendoswitch)) and defined(amd64):
+    type
+      SysThread* {.importc: "pthread_t",
+                  header: "<sys/types.h>" .} = distinct culong
+      Pthread_attr* {.importc: "pthread_attr_t",
+                    header: "<sys/types.h>".} = object
+        abi: array[56 div sizeof(clong), clong]
+  elif defined(openbsd) and defined(amd64):
+    type
+      SysThread* {.importc: "pthread_t", header: "<pthread.h>".} = object
+      Pthread_attr* {.importc: "pthread_attr_t",
+                       header: "<pthread.h>".} = object
+  else:
+    type
+      SysThread* {.importc: "pthread_t", header: "<sys/types.h>".} = int
+      Pthread_attr* {.importc: "pthread_attr_t",
+                       header: "<sys/types.h>".} = object
+  type
+    Timespec* {.importc: "struct timespec", header: "<time.h>".} = object
+      tv_sec*: Time
+      tv_nsec*: clong
+
+  proc pthread_attr_init*(a1: var Pthread_attr): cint {.
+    importc, header: pthreadh.}
+  proc pthread_attr_setstack*(a1: ptr Pthread_attr, a2: pointer, a3: int): cint {.
+    importc, header: pthreadh.}
+  proc pthread_attr_setstacksize*(a1: var Pthread_attr, a2: int): cint {.
+    importc, header: pthreadh.}
+  proc pthread_attr_destroy*(a1: var Pthread_attr): cint {.
+    importc, header: pthreadh.}
+
+  proc pthread_create*(a1: var SysThread, a2: var Pthread_attr,
+            a3: proc (x: pointer): pointer {.noconv.},
+            a4: pointer): cint {.importc: "pthread_create",
+            header: pthreadh.}
+  proc pthread_join*(a1: SysThread, a2: ptr pointer): cint {.
+    importc, header: pthreadh.}
+
+  proc pthread_cancel*(a1: SysThread): cint {.
+    importc: "pthread_cancel", header: pthreadh.}
+
+  type CpuSet* {.importc: "cpu_set_t", header: schedh.} = object
+     when defined(linux) and defined(amd64):
+       abi: array[1024 div (8 * sizeof(culong)), culong]
+
+  proc cpusetZero*(s: var CpuSet) {.importc: "CPU_ZERO", header: schedh.}
+  proc cpusetIncl*(cpu: cint; s: var CpuSet) {.
+    importc: "CPU_SET", header: schedh.}
+
+  when defined(android):
+    # libc of android doesn't implement pthread_setaffinity_np,
+    # it exposes pthread_gettid_np though, so we can use that in combination
+    # with sched_setaffinity to set the thread affinity.
+    type Pid* {.importc: "pid_t", header: "<sys/types.h>".} = int32 # From posix_other.nim
+
+    proc setAffinityTID*(tid: Pid; setsize: csize_t; s: var CpuSet) {.
+      importc: "sched_setaffinity", header: schedh.}
+
+    proc pthread_gettid_np*(thread: SysThread): Pid {.
+      importc: "pthread_gettid_np", header: pthreadh.}
+
+    proc setAffinity*(thread: SysThread; setsize: csize_t; s: var CpuSet) =
+      setAffinityTID(pthread_gettid_np(thread), setsize, s)
+  else:
+    proc setAffinity*(thread: SysThread; setsize: csize_t; s: var CpuSet) {.
+      importc: "pthread_setaffinity_np", header: pthreadh.}
+
+
+const
+  emulatedThreadVars* = compileOption("tlsEmulation")
+# we preallocate a fixed size for thread local storage, so that no heap
+# allocations are needed. Currently less than 16K are used on a 64bit machine.
+# We use `float` for proper alignment:
+const nimTlsSize {.intdefine.} = 16000
+type
+  ThreadLocalStorage* = array[0..(nimTlsSize div sizeof(float)), float]
+  PGcThread* = ptr GcThread
+  GcThread* {.pure, inheritable.} = object
+    when emulatedThreadVars:
+      tls*: ThreadLocalStorage
+    else:
+      nil
+    when hasSharedHeap:
+      next*, prev*: PGcThread
+      stackBottom*, stackTop*: pointer
+      stackSize*: int
+    else:
+      nil
+
+const hasAllocStack* = defined(zephyr) # maybe freertos too?
+
+type
+  Thread*[TArg] = object
+    core*: PGcThread
+    sys*: SysThread
+    when TArg is void:
+      dataFn*: proc () {.nimcall, gcsafe.}
+    else:
+      dataFn*: proc (m: TArg) {.nimcall, gcsafe.}
+      data*: TArg
+    when hasAllocStack:
+      rawStack*: pointer
+
+proc `=copy`*[TArg](x: var Thread[TArg], y: Thread[TArg]) {.error.}
diff --git a/lib/std/private/underscored_calls.nim b/lib/std/private/underscored_calls.nim
index f0bcbcc74..f853572b5 100644
--- a/lib/std/private/underscored_calls.nim
+++ b/lib/std/private/underscored_calls.nim
@@ -10,7 +10,9 @@
 
 ## This is an internal helper module. Do not use.
 
-import macros
+import std/macros
+
+proc underscoredCalls*(result, calls, arg0: NimNode)
 
 proc underscoredCall(n, arg0: NimNode): NimNode =
   proc underscorePos(n: NimNode): int =
@@ -19,13 +21,19 @@ proc underscoredCall(n, arg0: NimNode): NimNode =
     return 0
 
   if n.kind in nnkCallKinds:
-    result = copyNimNode(n)
-    result.add n[0]
+    if n[0].kind in {nnkIdent, nnkSym} and n[0].eqIdent("with"):
+      expectKind n[1], {nnkIdent, nnkSym}
 
-    let u = underscorePos(n)
-    for i in 1..u-1: result.add n[i]
-    result.add arg0
-    for i in u+1..n.len-1: result.add n[i]
+      result = newStmtList()
+      underscoredCalls(result, n[2 .. ^1].newStmtList, newDotExpr(arg0, n[1]))
+    else:
+      result = copyNimNode(n)
+      result.add n[0]
+
+      let u = underscorePos(n)
+      for i in 1..u-1: result.add n[i]
+      result.add arg0
+      for i in u+1..n.len-1: result.add n[i]
   elif n.kind in {nnkAsgn, nnkExprEqExpr}:
     var field = n[0]
     if n[0].kind == nnkDotExpr and n[0][0].eqIdent("_"):
diff --git a/lib/std/private/win_setenv.nim b/lib/std/private/win_setenv.nim
index 89bb0421f..66e199dfe 100644
--- a/lib/std/private/win_setenv.nim
+++ b/lib/std/private/win_setenv.nim
@@ -23,6 +23,9 @@ check errno_t vs cint
 
 when not defined(windows): discard
 else:
+  when defined(nimPreviewSlimSystem):
+    import std/widestrs
+
   type wchar_t  {.importc: "wchar_t".} = int16
 
   proc setEnvironmentVariableW*(lpName, lpValue: WideCString): int32 {.
@@ -30,25 +33,25 @@ else:
     # same as winlean.setEnvironmentVariableA
 
   proc c_getenv(varname: cstring): cstring {.importc: "getenv", header: "<stdlib.h>".}
-  proc c_wputenv(envstring: WideCString): cint {.importc: "_wputenv", header: "<stdlib.h>".}
-  proc c_wgetenv(varname: WideCString): WideCString {.importc: "_wgetenv", header: "<stdlib.h>".}
+  proc c_wputenv(envstring: ptr wchar_t): cint {.importc: "_wputenv", header: "<stdlib.h>".}
+  proc c_wgetenv(varname: ptr wchar_t): ptr wchar_t {.importc: "_wgetenv", header: "<stdlib.h>".}
 
   var errno {.importc, header: "<errno.h>".}: cint
   var genviron {.importc: "_environ".}: ptr ptr char
     # xxx `ptr UncheckedArray[WideCString]` did not work
 
-  proc wcstombs(wcstr: ptr char, mbstr: WideCString, count: csize_t): csize_t {.importc, header: "<stdlib.h>".}
+  proc wcstombs(wcstr: ptr char, mbstr: ptr wchar_t, count: csize_t): csize_t {.importc, header: "<stdlib.h>".}
     # xxx cint vs errno_t?
 
   proc setEnvImpl*(name: string, value: string, overwrite: cint): cint =
     const EINVAL = cint(22)
-    let wideName = newWideCString(name)
-    if overwrite == 0 and c_wgetenv(wideName) != nil:
+    let wideName: WideCString = newWideCString(name)
+    if overwrite == 0 and c_wgetenv(cast[ptr wchar_t](wideName)) != nil:
       return 0
 
     if value != "":
-      let envstring = name & "=" & value
-      let e = c_wputenv(newWideCString(envstring))
+      let envstring: WideCString = newWideCString(name & "=" & value)
+      let e = c_wputenv(cast[ptr wchar_t](envstring))
       if e != 0:
         errno = EINVAL
         return -1
@@ -59,19 +62,19 @@ else:
     SetEnvironmentVariableA doesn't update `_environ`,
     so we have to do these terrible things.
     ]#
-    let envstring = name & "=  "
-    if c_wputenv(newWideCString(envstring)) != 0:
+    let envstring: WideCString = newWideCString(name & "=  ")
+    if c_wputenv(cast[ptr wchar_t](envstring)) != 0:
       errno = EINVAL
       return -1
     # Here lies the documentation we blatently ignore to make this work.
-    var s = c_wgetenv(wideName)
+    var s = cast[WideCString](c_wgetenv(cast[ptr wchar_t](wideName)))
     s[0] = Utf16Char('\0')
     #[
     This would result in a double null termination, which normally signifies the
     end of the environment variable list, so we stick a completely empty
     environment variable into the list instead.
     ]#
-    s = c_wgetenv(wideName)
+    s = cast[WideCString](c_wgetenv(cast[ptr wchar_t](wideName)))
     s[1] = Utf16Char('=')
     #[
     If genviron is null, the MBCS environment has not been initialized
@@ -85,15 +88,15 @@ else:
       # in the current codepage. Skip updating MBCS environment in this case.
       # For some reason, second `wcstombs` can find non-convertible characters
       # that the first `wcstombs` cannot.
-      let requiredSizeS = wcstombs(nil, wideName, 0)
+      let requiredSizeS = wcstombs(nil, cast[ptr wchar_t](wideName), 0)
       if requiredSizeS != high(csize_t):
         let requiredSize = requiredSizeS.int
         var buf = newSeq[char](requiredSize + 1)
         let buf2 = buf[0].addr
-        if wcstombs(buf2, wideName, csize_t(requiredSize + 1)) != high(csize_t):
-          var ptrToEnv = c_getenv(buf2)
+        if wcstombs(buf2, cast[ptr wchar_t](wideName), csize_t(requiredSize + 1)) != high(csize_t):
+          var ptrToEnv = c_getenv(cast[cstring](buf2))
           ptrToEnv[0] = '\0'
-          ptrToEnv = c_getenv(buf2)
+          ptrToEnv = c_getenv(cast[cstring](buf2))
           ptrToEnv[1] = '='
 
     # And now, we have to update the outer environment to have a proper empty value.
diff --git a/lib/std/setutils.nim b/lib/std/setutils.nim
index 4664d6dcc..8e7bc6a92 100644
--- a/lib/std/setutils.nim
+++ b/lib/std/setutils.nim
@@ -14,7 +14,7 @@
 ## * `std/packedsets <packedsets.html>`_
 ## * `std/sets <sets.html>`_
 
-import typetraits, macros
+import std/[typetraits, macros]
 
 #[
   type SetElement* = char|byte|bool|int16|uint16|enum|uint8|int8
diff --git a/lib/std/sha1.nim b/lib/std/sha1.nim
index 50175024c..213af4229 100644
--- a/lib/std/sha1.nim
+++ b/lib/std/sha1.nim
@@ -26,8 +26,11 @@ runnableExamples("-r:off"):
     b = parseSecureHash("10DFAEBF6BFDBC7939957068E2EFACEC4972933C")
   assert a == b, "files don't match"
 
-import strutils
-from endians import bigEndian32, bigEndian64
+
+{.deprecated: "use command `nimble install checksums` and import `checksums/sha1` instead".}
+
+import std/strutils
+from std/endians import bigEndian32, bigEndian64
 
 when defined(nimPreviewSlimSystem):
   import std/syncio
@@ -281,4 +284,4 @@ proc `==`*(a, b: SecureHash): bool =
 
 proc isValidSha1Hash*(s: string): bool =
   ## Checks if a string is a valid sha1 hash sum.
-  s.len == 40 and allCharsInSet(s, HexDigits)
+  s.len == 40 and allCharsInSet(s, HexDigits)
\ No newline at end of file
diff --git a/lib/std/socketstreams.nim b/lib/std/socketstreams.nim
index 5c882858d..45e906795 100644
--- a/lib/std/socketstreams.nim
+++ b/lib/std/socketstreams.nim
@@ -31,39 +31,40 @@
 ## Examples
 ## ========
 ##
-## .. code-block:: Nim
-##  import std/socketstreams
+##   ```Nim
+##   import std/socketstreams
 ##
-##  var
-##    socket = newSocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
-##    stream = newReadSocketStream(socket)
-##  socket.sendTo("127.0.0.1", Port(12345), "SOME REQUEST")
-##  echo stream.readLine() # Will call `recv`
-##  stream.setPosition(0)
-##  echo stream.readLine() # Will return the read line from the buffer
-##  stream.resetStream() # Buffer is now empty, position is 0
-##  echo stream.readLine() # Will call `recv` again
-##  stream.close() # Closes the socket
+##   var
+##     socket = newSocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
+##     stream = newReadSocketStream(socket)
+##   socket.sendTo("127.0.0.1", Port(12345), "SOME REQUEST")
+##   echo stream.readLine() # Will call `recv`
+##   stream.setPosition(0)
+##   echo stream.readLine() # Will return the read line from the buffer
+##   stream.resetStream() # Buffer is now empty, position is 0
+##   echo stream.readLine() # Will call `recv` again
+##   stream.close() # Closes the socket
+##   ```
 ##
-## .. code-block:: Nim
+##   ```Nim
+##   import std/socketstreams
 ##
-##  import std/socketstreams
-##
-##  var socket = newSocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
-##  socket.connect("127.0.0.1", Port(12345))
-##  var sendStream = newWriteSocketStream(socket)
-##  sendStream.write "NOM"
-##  sendStream.setPosition(1)
-##  echo sendStream.peekStr(2) # OM
-##  sendStream.write "I"
-##  sendStream.setPosition(0)
-##  echo sendStream.readStr(3) # NIM
-##  echo sendStream.getPosition() # 3
-##  sendStream.flush() # This actually performs the writing to the socket
-##  sendStream.setPosition(1)
-##  sendStream.write "I" # Throws an error as we can't write into an already sent buffer
-
-import net, streams
+##   var socket = newSocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)
+##   socket.connect("127.0.0.1", Port(12345))
+##   var sendStream = newWriteSocketStream(socket)
+##   sendStream.write "NOM"
+##   sendStream.setPosition(1)
+##   echo sendStream.peekStr(2) # OM
+##   sendStream.write "I"
+##   sendStream.setPosition(0)
+##   echo sendStream.readStr(3) # NIM
+##   echo sendStream.getPosition() # 3
+##   sendStream.flush() # This actually performs the writing to the socket
+##   sendStream.setPosition(1)
+##   sendStream.write "I" # Throws an error as we can't write into an already sent buffer
+##   ```
+
+import std/[net, streams]
 
 type
   ReadSocketStream* = ref ReadSocketStreamObj
@@ -146,7 +147,7 @@ proc wsFlush(s: Stream) =
   s.lastFlush = s.buf.len
 
 proc rsClose(s: Stream) =
-  {.cast(tags: []).}:
+  {.cast(raises: [IOError, OSError]), cast(tags: []).}: # todo fixme maybe do something?
     var s = ReadSocketStream(s)
     s.data.close()
 
diff --git a/lib/std/staticos.nim b/lib/std/staticos.nim
new file mode 100644
index 000000000..2617c6913
--- /dev/null
+++ b/lib/std/staticos.nim
@@ -0,0 +1,13 @@
+## This module implements path handling like os module but works at only compile-time.
+## This module works even when cross compiling to OS that is not supported by os module.
+
+proc staticFileExists*(filename: string): bool {.compileTime.} =
+  ## Returns true if `filename` exists and is a regular file or symlink.
+  ##
+  ## Directories, device files, named pipes and sockets return false.
+  discard
+
+proc staticDirExists*(dir: string): bool {.compileTime.} =
+  ## Returns true if the directory `dir` exists. If `dir` is a file, false
+  ## is returned. Follows symlinks.
+  discard
diff --git a/lib/std/strbasics.nim b/lib/std/strbasics.nim
index be1dd7a58..b2c36a4be 100644
--- a/lib/std/strbasics.nim
+++ b/lib/std/strbasics.nim
@@ -23,8 +23,8 @@ proc add*(x: var string, y: openArray[char]) =
   # Use `{.noalias.}` ?
   let n = x.len
   x.setLen n + y.len
-    # pending https://github.com/nim-lang/Nim/issues/14655#issuecomment-643671397
-    # use x.setLen(n + y.len, isInit = false)
+    # pending #19727
+    # setLen unnecessarily zeros memory
   var i = 0
   while i < y.len:
     x[n + i] = y[i]
diff --git a/lib/std/sums.nim b/lib/std/sums.nim
deleted file mode 100644
index a6ce1b85d..000000000
--- a/lib/std/sums.nim
+++ /dev/null
@@ -1,80 +0,0 @@
-#
-#
-#            Nim's Runtime Library
-#        (c) Copyright 2019 b3liever
-#
-#    See the file "copying.txt", included in this
-#    distribution, for details about the copyright.
-
-## Accurate summation functions.
-
-{.deprecated: "use the nimble package `sums` instead.".}
-
-runnableExamples:
-  import std/math
-
-  template `~=`(x, y: float): bool = abs(x - y) < 1e-4
-
-  let
-    n = 1_000_000
-    first = 1e10
-    small = 0.1
-  var data = @[first]
-  for _ in 1 .. n:
-    data.add(small)
-
-  let result = first + small * n.float
-
-  doAssert abs(sum(data) - result) > 0.3
-  doAssert sumKbn(data) ~= result
-  doAssert sumPairs(data) ~= result
-
-## See also
-## ========
-## * `math module <math.html>`_ for a standard `sum proc <math.html#sum,openArray[T]>`_
-
-func sumKbn*[T](x: openArray[T]): T =
-  ## Kahan-Babuška-Neumaier summation: O(1) error growth, at the expense
-  ## of a considerable increase in computational cost.
-  ##
-  ## See:
-  ## * https://en.wikipedia.org/wiki/Kahan_summation_algorithm#Further_enhancements
-  if len(x) == 0: return
-  var sum = x[0]
-  var c = T(0)
-  for i in 1 ..< len(x):
-    let xi = x[i]
-    let t = sum + xi
-    if abs(sum) >= abs(xi):
-      c += (sum - t) + xi
-    else:
-      c += (xi - t) + sum
-    sum = t
-  result = sum + c
-
-func sumPairwise[T](x: openArray[T], i0, n: int): T =
-  if n < 128:
-    result = x[i0]
-    for i in i0 + 1 ..< i0 + n:
-      result += x[i]
-  else:
-    let n2 = n div 2
-    result = sumPairwise(x, i0, n2) + sumPairwise(x, i0 + n2, n - n2)
-
-func sumPairs*[T](x: openArray[T]): T =
-  ## Pairwise (cascade) summation of `x[i0:i0+n-1]`, with O(log n) error growth
-  ## (vs O(n) for a simple loop) with negligible performance cost if
-  ## the base case is large enough.
-  ##
-  ## See, e.g.:
-  ## * https://en.wikipedia.org/wiki/Pairwise_summation
-  ## * Higham, Nicholas J. (1993), "The accuracy of floating point
-  ##   summation", SIAM Journal on Scientific Computing 14 (4): 783–799.
-  ##
-  ## In fact, the root-mean-square error growth, assuming random roundoff
-  ## errors, is only O(sqrt(log n)), which is nearly indistinguishable from O(1)
-  ## in practice. See:
-  ## * Manfred Tasche and Hansmartin Zeuner, Handbook of
-  ##   Analytic-Computational Methods in Applied Mathematics (2000).
-  let n = len(x)
-  if n == 0: T(0) else: sumPairwise(x, 0, n)
diff --git a/lib/std/symlinks.nim b/lib/std/symlinks.nim
new file mode 100644
index 000000000..dbe908612
--- /dev/null
+++ b/lib/std/symlinks.nim
@@ -0,0 +1,33 @@
+## This module implements symlink (symbolic link) handling.
+
+## .. importdoc:: os.nim
+
+from std/paths import Path, ReadDirEffect
+
+from std/private/ossymlinks import symlinkExists, createSymlink, expandSymlink
+
+proc symlinkExists*(link: Path): bool {.inline, tags: [ReadDirEffect], sideEffect.} =
+  ## Returns true if the symlink `link` exists. Will return true
+  ## regardless of whether the link points to a directory or file.
+  result = symlinkExists(link.string)
+
+proc createSymlink*(src, dest: Path) {.inline.} =
+  ## Create a symbolic link at `dest` which points to the item specified
+  ## by `src`. On most operating systems, will fail if a link already exists.
+  ##
+  ## .. warning:: Some OS's (such as Microsoft Windows) restrict the creation
+  ##   of symlinks to root users (administrators) or users with developer mode enabled.
+  ##
+  ## See also:
+  ## * `createHardlink proc`_
+  ## * `expandSymlink proc`_
+  createSymlink(src.string, dest.string)
+
+proc expandSymlink*(symlinkPath: Path): Path {.inline.} =
+  ## Returns a string representing the path to which the symbolic link points.
+  ##
+  ## On Windows this is a noop, `symlinkPath` is simply returned.
+  ##
+  ## See also:
+  ## * `createSymlink proc`_
+  result = Path(expandSymlink(symlinkPath.string))
diff --git a/lib/std/syncio.nim b/lib/std/syncio.nim
index 22e981198..c34a025af 100644
--- a/lib/std/syncio.nim
+++ b/lib/std/syncio.nim
@@ -12,6 +12,8 @@
 include system/inclrtl
 import std/private/since
 import std/formatfloat
+when defined(windows):
+  import std/widestrs
 
 # ----------------- IO Part ------------------------------------------------
 type
@@ -36,8 +38,15 @@ type
                          ## at the end. If the file does not exist, it
                          ## will be created.
 
-  FileHandle* = cint ## type that represents an OS file handle; this is
-                      ## useful for low-level file access
+  FileHandle* = cint ## The type that represents an OS file handle; this is
+                      ## useful for low-level file access.
+
+  FileSeekPos* = enum ## Position relative to which seek should happen.
+                      # The values are ordered so that they match with stdio
+                      # SEEK_SET, SEEK_CUR and SEEK_END respectively.
+    fspSet            ## Seek to absolute value
+    fspCur            ## Seek relative to current position
+    fspEnd            ## Seek relative to end
 
 # text file handling:
 when not defined(nimscript) and not defined(js):
@@ -96,7 +105,7 @@ proc c_feof(f: File): cint {.
   importc: "feof", header: "<stdio.h>".}
 
 when not declared(c_fwrite):
-  proc c_fwrite(buf: pointer, size, n: csize_t, f: File): cint {.
+  proc c_fwrite(buf: pointer, size, n: csize_t, f: File): csize_t {.
     importc: "fwrite", header: "<stdio.h>".}
 
 # C routine that is used here:
@@ -142,21 +151,11 @@ proc c_fprintf(f: File, frmt: cstring): cint {.
 proc c_fputc(c: char, f: File): cint {.
   importc: "fputc", header: "<stdio.h>".}
 
-# When running nim in android app, stdout goes nowhere, so echo gets ignored
-# To redirect echo to the android logcat, use -d:androidNDK
-when defined(androidNDK):
-  const ANDROID_LOG_VERBOSE = 2.cint
-  proc android_log_print(prio: cint, tag: cstring, fmt: cstring): cint
-    {.importc: "__android_log_print", header: "<android/log.h>", varargs, discardable.}
-
-template sysFatal(exc, msg) =
-  raise newException(exc, msg)
-
 proc raiseEIO(msg: string) {.noinline, noreturn.} =
-  sysFatal(IOError, msg)
+  raise newException(IOError, msg)
 
 proc raiseEOF() {.noinline, noreturn.} =
-  sysFatal(EOFError, "EOF reached")
+  raise newException(EOFError, "EOF reached")
 
 proc strerror(errnum: cint): cstring {.importc, header: "<string.h>".}
 
@@ -244,7 +243,7 @@ when defined(windows):
     # machine. We also enable `setConsoleOutputCP(65001)` now by default.
     # But we cannot call printf directly as the string might contain \0.
     # So we have to loop over all the sections separated by potential \0s.
-    var i = c_fprintf(f, "%s", s)
+    var i = int c_fprintf(f, "%s", s)
     while i < s.len:
       if s[i] == '\0':
         let w = c_fputc('\0', f)
@@ -321,7 +320,7 @@ elif defined(windows):
 const
   BufSize = 4000
 
-proc close*(f: File) {.tags: [], gcsafe.} =
+proc close*(f: File) {.tags: [], gcsafe, sideEffect.} =
   ## Closes the file.
   if not f.isNil:
     discard c_fclose(f)
@@ -357,12 +356,12 @@ proc getOsFileHandle*(f: File): FileHandle =
 
 when defined(nimdoc) or (defined(posix) and not defined(nimscript)) or defined(windows):
   proc setInheritable*(f: FileHandle, inheritable: bool): bool =
-    ## control whether a file handle can be inherited by child processes. Returns
+    ## Controls whether a file handle can be inherited by child processes. Returns
     ## `true` on success. This requires the OS file handle, which can be
     ## retrieved via `getOsFileHandle <#getOsFileHandle,File>`_.
     ##
     ## This procedure is not guaranteed to be available for all platforms. Test for
-    ## availability with `declared() <system.html#declared,untyped>`.
+    ## availability with `declared() <system.html#declared,untyped>`_.
     when SupportIoctlInheritCtl:
       result = c_ioctl(f, if inheritable: FIONCLEX else: FIOCLEX) != -1
     elif defined(freertos) or defined(zephyr):
@@ -388,7 +387,7 @@ proc readLine*(f: File, line: var string): bool {.tags: [ReadIOEffect],
   proc c_memchr(s: pointer, c: cint, n: csize_t): pointer {.
     importc: "memchr", header: "<string.h>".}
 
-  when defined(windows) and not defined(useWinAnsi):
+  when defined(windows):
     proc readConsole(hConsoleInput: FileHandle, lpBuffer: pointer,
                      nNumberOfCharsToRead: int32,
                      lpNumberOfCharsRead: ptr int32,
@@ -420,7 +419,7 @@ proc readLine*(f: File, line: var string): bool {.tags: [ReadIOEffect],
     if f.isatty:
       const numberOfCharsToRead = 2048
       var numberOfCharsRead = 0'i32
-      var buffer = newWideCString("", numberOfCharsToRead)
+      var buffer = newWideCString(numberOfCharsToRead)
       if readConsole(getOsFileHandle(f), addr(buffer[0]),
         numberOfCharsToRead, addr(numberOfCharsRead), nil) == 0:
         var error = getLastError()
@@ -465,7 +464,7 @@ proc readLine*(f: File, line: var string): bool {.tags: [ReadIOEffect],
     while true:
       # fixes #9634; this pattern may need to be abstracted as a template if reused;
       # likely other io procs need this for correctness.
-      fgetsSuccess = c_fgets(addr line[pos], sp.cint, f) != nil
+      fgetsSuccess = c_fgets(cast[cstring](addr line[pos]), sp.cint, f) != nil
       if fgetsSuccess: break
       when not defined(nimscript):
         if errno == EINTR:
@@ -478,15 +477,16 @@ proc readLine*(f: File, line: var string): bool {.tags: [ReadIOEffect],
     let m = c_memchr(addr line[pos], '\L'.ord, cast[csize_t](sp))
     if m != nil:
       # \l found: Could be our own or the one by fgets, in any case, we're done
-      var last = cast[ByteAddress](m) - cast[ByteAddress](addr line[0])
+      var last = cast[int](m) - cast[int](addr line[0])
       if last > 0 and line[last-1] == '\c':
         line.setLen(last-1)
         return last > 1 or fgetsSuccess
-        # We have to distinguish between two possible cases:
+      elif last > 0 and line[last-1] == '\0':
+        # We have to distinguish among three possible cases:
         # \0\l\0 => line ending in a null character.
         # \0\l\l => last line without newline, null was put there by fgets.
-      elif last > 0 and line[last-1] == '\0':
-        if last < pos + sp - 1 and line[last+1] != '\0':
+        #   \0\l => last line without newline, null was put there by fgets.
+        if last >= pos + sp - 1 or line[last+1] != '\0': # bug #21273
           dec last
       line.setLen(last)
       return last > 0 or fgetsSuccess
@@ -571,7 +571,7 @@ proc readAllFile(file: File, len: int64): string =
   result = newString(len)
   let bytes = readBuffer(file, addr(result[0]), len)
   if endOfFile(file):
-    if bytes < len:
+    if bytes.int64 < len:
       result.setLen(bytes)
   else:
     # We read all the bytes but did not reach the EOF
@@ -609,7 +609,7 @@ proc writeLine*[Ty](f: File, x: varargs[Ty, `$`]) {.inline,
 
 # interface to the C procs:
 
-when defined(windows) and not defined(useWinAnsi):
+when defined(windows):
   when defined(cpp):
     proc wfopen(filename, mode: WideCString): pointer {.
       importcpp: "_wfopen((const wchar_t*)#, (const wchar_t*)#)", nodecl.}
@@ -648,6 +648,9 @@ const
         ""
     else:
       ""
+  RawFormatOpen: array[FileMode, cstring] = [
+    # used for open by FileHandle, which calls `fdopen`
+    cstring("rb"), "wb", "w+b", "r+b", "ab"]
   FormatOpen: array[FileMode, cstring] = [
     cstring("rb" & NoInheritFlag), "wb" & NoInheritFlag, "w+b" & NoInheritFlag,
     "r+b" & NoInheritFlag, "ab" & NoInheritFlag
@@ -715,7 +718,7 @@ proc open*(f: var File, filename: string,
 
     result = true
     f = cast[File](p)
-    if bufSize > 0 and bufSize <= high(cint).int:
+    if bufSize > 0 and bufSize.uint <= high(uint):
       discard c_setvbuf(f, nil, IOFBF, cast[csize_t](bufSize))
     elif bufSize == 0:
       discard c_setvbuf(f, nil, IONBF, 0)
@@ -749,7 +752,7 @@ proc open*(f: var File, filehandle: FileHandle,
         filehandle) else: filehandle
     if not setInheritable(oshandle, false):
       return false
-  f = c_fdopen(filehandle, FormatOpen[mode])
+  f = c_fdopen(filehandle, RawFormatOpen[mode])
   result = f != nil
 
 proc open*(filename: string,
@@ -761,9 +764,9 @@ proc open*(filename: string,
   ##
   ## The file handle associated with the resulting `File` is not inheritable.
   if not open(result, filename, mode, bufSize):
-    sysFatal(IOError, "cannot open: " & filename)
+    raise newException(IOError, "cannot open: " & filename)
 
-proc setFilePos*(f: File, pos: int64, relativeTo: FileSeekPos = fspSet) {.benign.} =
+proc setFilePos*(f: File, pos: int64, relativeTo: FileSeekPos = fspSet) {.benign, sideEffect.} =
   ## Sets the position of the file pointer that is used for read/write
   ## operations. The file's first byte has the index zero.
   if c_fseek(f, pos, cint(relativeTo)) != 0:
@@ -791,52 +794,6 @@ proc setStdIoUnbuffered*() {.tags: [], benign.} =
   when declared(stdin):
     discard c_setvbuf(stdin, nil, IONBF, 0)
 
-when declared(stdout):
-  when defined(windows) and compileOption("threads"):
-    proc addSysExitProc(quitProc: proc() {.noconv.}) {.importc: "atexit", header: "<stdlib.h>".}
-
-    const insideRLocksModule = false
-    include "system/syslocks"
-
-
-    var echoLock: SysLock
-    initSysLock echoLock
-    addSysExitProc(proc() {.noconv.} = deinitSys(echoLock))
-
-  const stdOutLock = not defined(windows) and
-                     not defined(android) and
-                     not defined(nintendoswitch) and
-                     not defined(freertos) and
-                     not defined(zephyr) and
-                     hostOS != "any"
-
-  proc echoBinSafe(args: openArray[string]) {.compilerproc.} =
-    when defined(androidNDK):
-      var s = ""
-      for arg in args:
-        s.add arg
-      android_log_print(ANDROID_LOG_VERBOSE, "nim", s)
-    else:
-      # flockfile deadlocks some versions of Android 5.x.x
-      when stdOutLock:
-        proc flockfile(f: File) {.importc, nodecl.}
-        proc funlockfile(f: File) {.importc, nodecl.}
-        flockfile(stdout)
-      when defined(windows) and compileOption("threads"):
-        acquireSys echoLock
-      for s in args:
-        when defined(windows):
-          writeWindows(stdout, s)
-        else:
-          discard c_fwrite(s.cstring, cast[csize_t](s.len), 1, stdout)
-      const linefeed = "\n"
-      discard c_fwrite(linefeed.cstring, linefeed.len, 1, stdout)
-      discard c_fflush(stdout)
-      when stdOutLock:
-        funlockfile(stdout)
-      when defined(windows) and compileOption("threads"):
-        releaseSys echoLock
-
 
 when defined(windows) and not defined(nimscript) and not defined(js):
   # work-around C's sucking abstraction:
@@ -854,14 +811,33 @@ when defined(windows) and not defined(nimscript) and not defined(js):
 
 when defined(windows) and appType == "console" and
     not defined(nimDontSetUtf8CodePage) and not defined(nimscript):
+  import std/exitprocs
+
   proc setConsoleOutputCP(codepage: cuint): int32 {.stdcall, dynlib: "kernel32",
     importc: "SetConsoleOutputCP".}
   proc setConsoleCP(wCodePageID: cuint): int32 {.stdcall, dynlib: "kernel32",
     importc: "SetConsoleCP".}
+  proc getConsoleOutputCP(): cuint {.stdcall, dynlib: "kernel32",
+    importc: "GetConsoleOutputCP".}
+  proc getConsoleCP(): cuint {.stdcall, dynlib: "kernel32",
+    importc: "GetConsoleCP".}
+
+  const Utf8codepage = 65001'u32
+
+  let
+    consoleOutputCP = getConsoleOutputCP()
+    consoleCP = getConsoleCP()
 
-  const Utf8codepage = 65001
-  discard setConsoleOutputCP(Utf8codepage)
-  discard setConsoleCP(Utf8codepage)
+  proc restoreConsoleOutputCP() = discard setConsoleOutputCP(consoleOutputCP)
+  proc restoreConsoleCP() = discard setConsoleCP(consoleCP)
+
+  if consoleOutputCP != Utf8codepage:
+    discard setConsoleOutputCP(Utf8codepage)
+    addExitProc(restoreConsoleOutputCP)
+
+  if consoleCP != Utf8codepage:
+    discard setConsoleCP(Utf8codepage)
+    addExitProc(restoreConsoleCP)
 
 proc readFile*(filename: string): string {.tags: [ReadIOEffect], benign.} =
   ## Opens a file named `filename` for reading, calls `readAll
@@ -876,7 +852,7 @@ proc readFile*(filename: string): string {.tags: [ReadIOEffect], benign.} =
     finally:
       close(f)
   else:
-    sysFatal(IOError, "cannot open: " & filename)
+    raise newException(IOError, "cannot open: " & filename)
 
 proc writeFile*(filename, content: string) {.tags: [WriteIOEffect], benign.} =
   ## Opens a file named `filename` for writing. Then writes the
@@ -889,7 +865,7 @@ proc writeFile*(filename, content: string) {.tags: [WriteIOEffect], benign.} =
     finally:
       close(f)
   else:
-    sysFatal(IOError, "cannot open: " & filename)
+    raise newException(IOError, "cannot open: " & filename)
 
 proc writeFile*(filename: string, content: openArray[byte]) {.since: (1, 1).} =
   ## Opens a file named `filename` for writing. Then writes the
@@ -898,7 +874,7 @@ proc writeFile*(filename: string, content: openArray[byte]) {.since: (1, 1).} =
   var f: File = nil
   if open(f, filename, fmWrite):
     try:
-      f.writeBuffer(unsafeAddr content[0], content.len)
+      discard f.writeBuffer(unsafeAddr content[0], content.len)
     finally:
       close(f)
   else:
@@ -919,7 +895,7 @@ proc readLines*(filename: string, n: Natural): seq[string] =
     finally:
       close(f)
   else:
-    sysFatal(IOError, "cannot open: " & filename)
+    raise newException(IOError, "cannot open: " & filename)
 
 template readLines*(filename: string): seq[
     string] {.deprecated: "use readLines with two arguments".} =
@@ -960,3 +936,7 @@ iterator lines*(f: File): string {.tags: [ReadIOEffect].} =
         result.lines += 1
   var res = newStringOfCap(80)
   while f.readLine(res): yield res
+
+template `&=`*(f: File, x: typed) =
+  ## An alias for `write`.
+  write(f, x)
diff --git a/lib/std/sysatomics.nim b/lib/std/sysatomics.nim
new file mode 100644
index 000000000..2f203b3eb
--- /dev/null
+++ b/lib/std/sysatomics.nim
@@ -0,0 +1,376 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2015 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+when defined(nimPreviewSlimSystem):
+  {.deprecated: "use `std/atomics` instead".}
+
+# Atomic operations for Nim.
+{.push stackTrace:off, profiler:off.}
+
+const
+  hasThreadSupport = compileOption("threads") and not defined(nimscript)
+const someGcc = defined(gcc) or defined(llvm_gcc) or defined(clang) or defined(nintendoswitch)
+const someVcc = defined(vcc) or defined(clang_cl)
+
+type
+  AtomType* = SomeNumber|pointer|ptr|char|bool
+    ## Type Class representing valid types for use with atomic procs
+
+when someGcc:
+  type AtomMemModel* = distinct cint
+
+  var ATOMIC_RELAXED* {.importc: "__ATOMIC_RELAXED", nodecl.}: AtomMemModel
+    ## No barriers or synchronization.
+  var ATOMIC_CONSUME* {.importc: "__ATOMIC_CONSUME", nodecl.}: AtomMemModel
+    ## Data dependency only for both barrier and
+    ## synchronization with another thread.
+  var ATOMIC_ACQUIRE* {.importc: "__ATOMIC_ACQUIRE", nodecl.}: AtomMemModel
+    ## Barrier to hoisting of code and synchronizes with
+    ## release (or stronger)
+    ## semantic stores from another thread.
+  var ATOMIC_RELEASE* {.importc: "__ATOMIC_RELEASE", nodecl.}: AtomMemModel
+    ## Barrier to sinking of code and synchronizes with
+    ## acquire (or stronger)
+    ## semantic loads from another thread.
+  var ATOMIC_ACQ_REL* {.importc: "__ATOMIC_ACQ_REL", nodecl.}: AtomMemModel
+    ## Full barrier in both directions and synchronizes
+    ## with acquire loads
+    ## and release stores in another thread.
+  var ATOMIC_SEQ_CST* {.importc: "__ATOMIC_SEQ_CST", nodecl.}: AtomMemModel
+    ## Full barrier in both directions and synchronizes
+    ## with acquire loads
+    ## and release stores in all threads.
+
+  proc atomicLoadN*[T: AtomType](p: ptr T, mem: AtomMemModel): T {.
+    importc: "__atomic_load_n", nodecl.}
+    ## This proc implements an atomic load operation. It returns the contents at p.
+    ## ATOMIC_RELAXED, ATOMIC_SEQ_CST, ATOMIC_ACQUIRE, ATOMIC_CONSUME.
+
+  proc atomicLoad*[T: AtomType](p, ret: ptr T, mem: AtomMemModel) {.
+    importc: "__atomic_load", nodecl.}
+    ## This is the generic version of an atomic load. It returns the contents at p in ret.
+
+  proc atomicStoreN*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel) {.
+    importc: "__atomic_store_n", nodecl.}
+    ## This proc implements an atomic store operation. It writes val at p.
+    ## ATOMIC_RELAXED, ATOMIC_SEQ_CST, and ATOMIC_RELEASE.
+
+  proc atomicStore*[T: AtomType](p, val: ptr T, mem: AtomMemModel) {.
+    importc: "__atomic_store", nodecl.}
+    ## This is the generic version of an atomic store. It stores the value of val at p
+
+  proc atomicExchangeN*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_exchange_n", nodecl.}
+    ## This proc implements an atomic exchange operation. It writes val at p,
+    ## and returns the previous contents at p.
+    ## ATOMIC_RELAXED, ATOMIC_SEQ_CST, ATOMIC_ACQUIRE, ATOMIC_RELEASE, ATOMIC_ACQ_REL
+
+  proc atomicExchange*[T: AtomType](p, val, ret: ptr T, mem: AtomMemModel) {.
+    importc: "__atomic_exchange", nodecl.}
+    ## This is the generic version of an atomic exchange. It stores the contents at val at p.
+    ## The original value at p is copied into ret.
+
+  proc atomicCompareExchangeN*[T: AtomType](p, expected: ptr T, desired: T,
+    weak: bool, success_memmodel: AtomMemModel, failure_memmodel: AtomMemModel): bool {.
+    importc: "__atomic_compare_exchange_n", nodecl.}
+    ## This proc implements an atomic compare and exchange operation. This compares the
+    ## contents at p with the contents at expected and if equal, writes desired at p.
+    ## If they are not equal, the current contents at p is written into expected.
+    ## Weak is true for weak compare_exchange, and false for the strong variation.
+    ## Many targets only offer the strong variation and ignore the parameter.
+    ## When in doubt, use the strong variation.
+    ## True is returned if desired is written at p and the execution is considered
+    ## to conform to the memory model specified by success_memmodel. There are no
+    ## restrictions on what memory model can be used here. False is returned otherwise,
+    ## and the execution is considered to conform to failure_memmodel. This memory model
+    ## cannot be __ATOMIC_RELEASE nor __ATOMIC_ACQ_REL. It also cannot be a stronger model
+    ## than that specified by success_memmodel.
+
+  proc atomicCompareExchange*[T: AtomType](p, expected, desired: ptr T,
+    weak: bool, success_memmodel: AtomMemModel, failure_memmodel: AtomMemModel): bool {.
+    importc: "__atomic_compare_exchange", nodecl.}
+    ## This proc implements the generic version of atomic_compare_exchange.
+    ## The proc is virtually identical to atomic_compare_exchange_n, except the desired
+    ## value is also a pointer.
+
+  ## Perform the operation return the new value, all memory models are valid
+  proc atomicAddFetch*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_add_fetch", nodecl.}
+  proc atomicSubFetch*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_sub_fetch", nodecl.}
+  proc atomicOrFetch*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_or_fetch", nodecl.}
+  proc atomicAndFetch*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_and_fetch", nodecl.}
+  proc atomicXorFetch*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_xor_fetch", nodecl.}
+  proc atomicNandFetch*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_nand_fetch", nodecl.}
+
+  ## Perform the operation return the old value, all memory models are valid
+  proc atomicFetchAdd*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_fetch_add", nodecl.}
+  proc atomicFetchSub*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_fetch_sub", nodecl.}
+  proc atomicFetchOr*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_fetch_or", nodecl.}
+  proc atomicFetchAnd*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_fetch_and", nodecl.}
+  proc atomicFetchXor*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_fetch_xor", nodecl.}
+  proc atomicFetchNand*[T: AtomType](p: ptr T, val: T, mem: AtomMemModel): T {.
+    importc: "__atomic_fetch_nand", nodecl.}
+
+  proc atomicTestAndSet*(p: pointer, mem: AtomMemModel): bool {.
+    importc: "__atomic_test_and_set", nodecl.}
+    ## This built-in function performs an atomic test-and-set operation on the byte at p.
+    ## The byte is set to some implementation defined nonzero "set" value and the return
+    ## value is true if and only if the previous contents were "set".
+    ## All memory models are valid.
+
+  proc atomicClear*(p: pointer, mem: AtomMemModel) {.
+    importc: "__atomic_clear", nodecl.}
+    ## This built-in function performs an atomic clear operation at p.
+    ## After the operation, at p contains 0.
+    ## ATOMIC_RELAXED, ATOMIC_SEQ_CST, ATOMIC_RELEASE
+
+  proc atomicThreadFence*(mem: AtomMemModel) {.
+    importc: "__atomic_thread_fence", nodecl.}
+    ## This built-in function acts as a synchronization fence between threads based
+    ## on the specified memory model. All memory orders are valid.
+
+  proc atomicSignalFence*(mem: AtomMemModel) {.
+    importc: "__atomic_signal_fence", nodecl.}
+    ## This built-in function acts as a synchronization fence between a thread and
+    ## signal handlers based in the same thread. All memory orders are valid.
+
+  proc atomicAlwaysLockFree*(size: int, p: pointer): bool {.
+    importc: "__atomic_always_lock_free", nodecl.}
+    ## This built-in function returns true if objects of size bytes always generate
+    ## lock free atomic instructions for the target architecture. size must resolve
+    ## to a compile-time constant and the result also resolves to a compile-time constant.
+    ## ptr is an optional pointer to the object that may be used to determine alignment.
+    ## A value of 0 indicates typical alignment should be used. The compiler may also
+    ## ignore this parameter.
+
+  proc atomicIsLockFree*(size: int, p: pointer): bool {.
+    importc: "__atomic_is_lock_free", nodecl.}
+    ## This built-in function returns true if objects of size bytes always generate
+    ## lock free atomic instructions for the target architecture. If it is not known
+    ## to be lock free a call is made to a runtime routine named __atomic_is_lock_free.
+    ## ptr is an optional pointer to the object that may be used to determine alignment.
+    ## A value of 0 indicates typical alignment should be used. The compiler may also
+    ## ignore this parameter.
+
+  template fence*() = atomicThreadFence(ATOMIC_SEQ_CST)
+elif someVcc:
+  type AtomMemModel* = distinct cint
+
+  const
+    ATOMIC_RELAXED* = 0.AtomMemModel
+    ATOMIC_CONSUME* = 1.AtomMemModel
+    ATOMIC_ACQUIRE* = 2.AtomMemModel
+    ATOMIC_RELEASE* = 3.AtomMemModel
+    ATOMIC_ACQ_REL* = 4.AtomMemModel
+    ATOMIC_SEQ_CST* = 5.AtomMemModel
+
+  proc `==`(x1, x2: AtomMemModel): bool {.borrow.}
+
+  proc readBarrier() {.importc: "_ReadBarrier", header: "<intrin.h>".}
+  proc writeBarrier() {.importc: "_WriteBarrier", header: "<intrin.h>".}
+  proc fence*() {.importc: "_ReadWriteBarrier", header: "<intrin.h>".}
+
+  when defined(cpp):
+    proc interlockedCompareExchange64(p: pointer; exchange, comparand: int64): int64
+      {.importcpp: "_InterlockedCompareExchange64(static_cast<NI64 volatile *>(#), #, #)", header: "<intrin.h>".}
+    proc interlockedCompareExchange32(p: pointer; exchange, comparand: int32): int32
+      {.importcpp: "_InterlockedCompareExchange(static_cast<long volatile *>(#), #, #)", header: "<intrin.h>".}
+    proc interlockedCompareExchange8(p: pointer; exchange, comparand: byte): byte
+      {.importcpp: "_InterlockedCompareExchange8(static_cast<char volatile *>(#), #, #)", header: "<intrin.h>".}
+    proc interlockedExchange8(location: pointer; desired: int8): int8 {.importcpp: "_InterlockedExchange8(static_cast<NI8 volatile *>(#), #)", header: "<intrin.h>".}
+    proc interlockedExchange16(location: pointer; desired: int16): int16 {.importcpp: "_InterlockedExchange16(static_cast<NI16 volatile *>(#), #)", header: "<intrin.h>".}
+    proc interlockedExchange32(location: pointer; desired: int32): int32 {.importcpp: "_InterlockedExchange(static_cast<long volatile *>(#), #)", header: "<intrin.h>".}
+    proc interlockedExchange64(location: pointer; desired: int64): int64 {.importcpp: "_InterlockedExchange64(static_cast<NI64 volatile *>(#), #)", header: "<intrin.h>".}
+  else:
+    proc interlockedCompareExchange64(p: pointer; exchange, comparand: int64): int64
+      {.importc: "_InterlockedCompareExchange64", header: "<intrin.h>".}
+    proc interlockedCompareExchange32(p: pointer; exchange, comparand: int32): int32
+      {.importc: "_InterlockedCompareExchange", header: "<intrin.h>".}
+    proc interlockedCompareExchange8(p: pointer; exchange, comparand: byte): byte
+      {.importc: "_InterlockedCompareExchange8", header: "<intrin.h>".}
+
+    proc interlockedExchange8(location: pointer; desired: int8): int8 {.importc: "_InterlockedExchange8", header: "<intrin.h>".}
+    proc interlockedExchange16(location: pointer; desired: int16): int16 {.importc: "_InterlockedExchange16", header: "<intrin.h>".}
+    proc interlockedExchange32(location: pointer; desired: int32): int32 {.importc: "_InterlockedExchange", header: "<intrin.h>".}
+    proc interlockedExchange64(location: pointer; desired: int64): int64 {.importc: "_InterlockedExchange64", header: "<intrin.h>".}
+
+
+  template barrier(mem: AtomMemModel) =
+    when mem == ATOMIC_RELAXED: discard
+    elif mem == ATOMIC_CONSUME: readBarrier()
+    elif mem == ATOMIC_ACQUIRE: writeBarrier()
+    elif mem == ATOMIC_RELEASE: fence()
+    elif mem == ATOMIC_ACQ_REL: fence()
+    elif mem == ATOMIC_SEQ_CST: fence()
+
+  proc atomicStoreN*[T: AtomType](p: ptr T, val: T, mem: static[AtomMemModel]) =
+    barrier(mem)
+    p[] = val
+
+  proc atomicLoadN*[T: AtomType](p: ptr T, mem: static[AtomMemModel]): T =
+    result = p[]
+    barrier(mem)
+
+  proc atomicCompareExchangeN*[T: ptr](p, expected: ptr T, desired: T,
+    weak: bool, success_memmodel: AtomMemModel, failure_memmodel: AtomMemModel): bool =
+    when sizeof(T) == 8:
+      interlockedCompareExchange64(p, cast[int64](desired), cast[int64](expected)) ==
+        cast[int64](expected)
+    elif sizeof(T) == 4:
+      interlockedCompareExchange32(p, cast[int32](desired), cast[int32](expected)) ==
+        cast[int32](expected)
+
+  proc atomicExchangeN*[T: ptr](p: ptr T, val: T, mem: AtomMemModel): T =
+    when sizeof(T) == 8:
+      cast[T](interlockedExchange64(p, cast[int64](val)))
+    elif sizeof(T) == 4:
+      cast[T](interlockedExchange32(p, cast[int32](val)))
+  when defined(cpp):
+    when sizeof(int) == 8:
+      proc addAndFetch*(p: ptr int, val: int): int {.
+        importcpp: "_InterlockedExchangeAdd64(static_cast<NI volatile *>(#), #)",
+        header: "<intrin.h>".}
+    else:
+      proc addAndFetch*(p: ptr int, val: int): int {.
+        importcpp: "_InterlockedExchangeAdd(reinterpret_cast<long volatile *>(#), static_cast<long>(#))",
+        header: "<intrin.h>".}
+  else:
+    when sizeof(int) == 8:
+      proc addAndFetch*(p: ptr int, val: int): int {.
+        importc: "_InterlockedExchangeAdd64", header: "<intrin.h>".}
+    else:
+      proc addAndFetch*(p: ptr int, val: int): int {.
+        importc: "_InterlockedExchangeAdd", header: "<intrin.h>".}
+
+else:
+  proc addAndFetch*(p: ptr int, val: int): int {.inline.} =
+    inc(p[], val)
+    result = p[]
+
+
+proc atomicInc*(memLoc: var int, x: int = 1): int {.inline, discardable, raises: [], tags: [].} =
+  ## Atomically increments the integer by some `x`. It returns the new value.
+  when someGcc and hasThreadSupport:
+    result = atomicAddFetch(memLoc.addr, x, ATOMIC_SEQ_CST)
+  elif someVcc and hasThreadSupport:
+    result = addAndFetch(memLoc.addr, x)
+    inc(result, x)
+  else:
+    inc(memLoc, x)
+    result = memLoc
+
+proc atomicDec*(memLoc: var int, x: int = 1): int {.inline, discardable, raises: [], tags: [].} =
+  ## Atomically decrements the integer by some `x`. It returns the new value.
+  when someGcc and hasThreadSupport:
+    when declared(atomicSubFetch):
+      result = atomicSubFetch(memLoc.addr, x, ATOMIC_SEQ_CST)
+    else:
+      result = atomicAddFetch(memLoc.addr, -x, ATOMIC_SEQ_CST)
+  elif someVcc and hasThreadSupport:
+    result = addAndFetch(memLoc.addr, -x)
+    dec(result, x)
+  else:
+    dec(memLoc, x)
+    result = memLoc
+
+when someVcc:
+  proc cas*[T: bool|int|ptr](p: ptr T; oldValue, newValue: T): bool =
+    when sizeof(T) == 8:
+      interlockedCompareExchange64(p, cast[int64](newValue), cast[int64](oldValue)) ==
+        cast[int64](oldValue)
+    elif sizeof(T) == 4:
+      interlockedCompareExchange32(p, cast[int32](newValue), cast[int32](oldValue)) ==
+        cast[int32](oldValue)
+    elif sizeof(T) == 1:
+      interlockedCompareExchange8(p, cast[byte](newValue), cast[byte](oldValue)) ==
+        cast[byte](oldValue)
+    else:
+      {.error: "invalid CAS instruction".}
+
+elif defined(tcc):
+  when defined(amd64):
+    {.emit:"""
+static int __tcc_cas(int *ptr, int oldVal, int newVal)
+{
+    unsigned char ret;
+    __asm__ __volatile__ (
+            "  lock\n"
+            "  cmpxchgq %2,%1\n"
+            "  sete %0\n"
+            : "=q" (ret), "=m" (*ptr)
+            : "r" (newVal), "m" (*ptr), "a" (oldVal)
+            : "memory");
+
+    return ret;
+}
+""".}
+  else:
+    #assert sizeof(int) == 4
+    {.emit:"""
+static int __tcc_cas(int *ptr, int oldVal, int newVal)
+{
+    unsigned char ret;
+    __asm__ __volatile__ (
+            "  lock\n"
+            "  cmpxchgl %2,%1\n"
+            "  sete %0\n"
+            : "=q" (ret), "=m" (*ptr)
+            : "r" (newVal), "m" (*ptr), "a" (oldVal)
+            : "memory");
+
+    return ret;
+}
+""".}
+
+  proc tcc_cas(p: ptr int; oldValue, newValue: int): bool
+    {.importc: "__tcc_cas", nodecl.}
+  proc cas*[T: bool|int|ptr](p: ptr T; oldValue, newValue: T): bool =
+    tcc_cas(cast[ptr int](p), cast[int](oldValue), cast[int](newValue))
+elif declared(atomicCompareExchangeN):
+  proc cas*[T: bool|int|ptr](p: ptr T; oldValue, newValue: T): bool =
+    atomicCompareExchangeN(p, oldValue.unsafeAddr, newValue, false, ATOMIC_SEQ_CST, ATOMIC_SEQ_CST)
+else:
+  # this is valid for GCC and Intel C++
+  proc cas*[T: bool|int|ptr](p: ptr T; oldValue, newValue: T): bool
+    {.importc: "__sync_bool_compare_and_swap", nodecl.}
+  # XXX is this valid for 'int'?
+
+
+when (defined(x86) or defined(amd64)) and someVcc:
+  proc cpuRelax* {.importc: "YieldProcessor", header: "<windows.h>".}
+elif (defined(x86) or defined(amd64)) and (someGcc or defined(bcc)):
+  proc cpuRelax* {.inline.} =
+    {.emit: """asm volatile("pause" ::: "memory");""".}
+elif someGcc or defined(tcc):
+  proc cpuRelax* {.inline.} =
+    {.emit: """asm volatile("" ::: "memory");""".}
+elif defined(icl):
+  proc cpuRelax* {.importc: "_mm_pause", header: "xmmintrin.h".}
+elif false:
+  from std/os import sleep
+
+  proc cpuRelax* {.inline.} = os.sleep(1)
+
+when not declared(fence) and hasThreadSupport:
+  # XXX fixme
+  proc fence*() {.inline.} =
+    var dummy: bool
+    discard cas(addr dummy, false, true)
+
+{.pop.}
diff --git a/lib/std/sysrand.nim b/lib/std/sysrand.nim
index ff62c920b..6f2c6b0c1 100644
--- a/lib/std/sysrand.nim
+++ b/lib/std/sysrand.nim
@@ -20,7 +20,7 @@
 ## | :---                 | ----:                 |
 ## | Windows              | `BCryptGenRandom`_    |
 ## | Linux                | `getrandom`_          |
-## | MacOSX               | `getentropy`_         |
+## | MacOSX               | `SecRandomCopyBytes`_ |
 ## | iOS                  | `SecRandomCopyBytes`_ |
 ## | OpenBSD              | `getentropy openbsd`_ |
 ## | FreeBSD              | `getrandom freebsd`_  |
@@ -57,16 +57,16 @@ runnableExamples:
 
 
 when not defined(js):
-  import os
+  import std/oserrors
 
 when defined(posix):
-  import posix
+  import std/posix
 
 when defined(nimPreviewSlimSystem):
   import std/assertions
 
 const
-  batchImplOS = defined(freebsd) or defined(openbsd) or defined(zephyr) or (defined(macosx) and not defined(ios))
+  batchImplOS = defined(freebsd) or defined(openbsd) or defined(zephyr)
   batchSize {.used.} = 256
 
 when batchImplOS:
@@ -168,8 +168,10 @@ elif defined(windows):
     result = randomBytes(addr dest[0], size)
 
 elif defined(linux) and not defined(nimNoGetRandom) and not defined(emscripten):
-  # TODO using let, pending bootstrap >= 1.4.0
-  var SYS_getrandom {.importc: "SYS_getrandom", header: "<sys/syscall.h>".}: clong
+  when (NimMajor, NimMinor) >= (1, 4):
+    let SYS_getrandom {.importc: "SYS_getrandom", header: "<sys/syscall.h>".}: clong
+  else:
+    var SYS_getrandom {.importc: "SYS_getrandom", header: "<sys/syscall.h>".}: clong
   const syscallHeader = """#include <unistd.h>
 #include <sys/syscall.h>"""
 
@@ -190,12 +192,11 @@ elif defined(linux) and not defined(nimNoGetRandom) and not defined(emscripten):
     while result < size:
       let readBytes = syscall(SYS_getrandom, addr dest[result], cint(size - result), 0).int
       if readBytes == 0:
-        doAssert false
+        raiseAssert "unreachable"
       elif readBytes > 0:
         inc(result, readBytes)
       else:
-        if osLastError().int in {EINTR, EAGAIN}:
-          discard
+        if osLastError().cint in [EINTR, EAGAIN]: discard
         else:
           result = -1
           break
@@ -231,8 +232,8 @@ elif defined(freebsd):
   proc getRandomImpl(p: pointer, size: int): int {.inline.} =
     result = getrandom(p, csize_t(size), 0)
 
-elif defined(ios):
-  {.passL: "-framework Security".}
+elif defined(ios) or defined(macosx):
+  {.passl: "-framework Security".}
 
   const errSecSuccess = 0 ## No error.
 
@@ -254,19 +255,6 @@ elif defined(ios):
 
     result = secRandomCopyBytes(nil, csize_t(size), addr dest[0])
 
-elif defined(macosx):
-  const sysrandomHeader = """#include <Availability.h>
-#include <sys/random.h>
-"""
-
-  proc getentropy(p: pointer, size: csize_t): cint {.importc: "getentropy", header: sysrandomHeader.}
-    # getentropy() fills a buffer with random data, which can be used as input
-    # for process-context pseudorandom generators like arc4random(3).
-    # The maximum buffer size permitted is 256 bytes.
-
-  proc getRandomImpl(p: pointer, size: int): int {.inline.} =
-    result = getentropy(p, csize_t(size)).int
-
 else:
   template urandomImpl(result: var int, dest: var openArray[byte]) =
     let size = dest.len
diff --git a/lib/std/tasks.nim b/lib/std/tasks.nim
index ac35e26bf..7e59747f5 100644
--- a/lib/std/tasks.nim
+++ b/lib/std/tasks.nim
@@ -11,7 +11,6 @@
 ## A `Task` should be only owned by a single Thread, it cannot be shared by threads.
 
 import std/[macros, isolation, typetraits]
-import system/ansi_c
 
 when defined(nimPreviewSlimSystem):
   import std/assertions
@@ -62,24 +61,33 @@ when compileOption("threads"):
 
 type
   Task* = object ## `Task` contains the callback and its arguments.
-    callback: proc (args: pointer) {.nimcall, gcsafe.}
+    callback: proc (args, res: pointer) {.nimcall, gcsafe.}
     args: pointer
     destroy: proc (args: pointer) {.nimcall, gcsafe.}
 
 
 proc `=copy`*(x: var Task, y: Task) {.error.}
 
-proc `=destroy`*(t: var Task) {.inline, gcsafe.} =
-  ## Frees the resources allocated for a `Task`.
-  if t.args != nil:
-    if t.destroy != nil:
-      t.destroy(t.args)
-    c_free(t.args)
-
-proc invoke*(task: Task) {.inline, gcsafe.} =
+const arcLike = defined(gcArc) or defined(gcAtomicArc) or defined(gcOrc)
+when defined(nimAllowNonVarDestructor) and arcLike:
+  proc `=destroy`*(t: Task) {.inline, gcsafe.} =
+    ## Frees the resources allocated for a `Task`.
+    if t.args != nil:
+      if t.destroy != nil:
+        t.destroy(t.args)
+      deallocShared(t.args)
+else:
+  proc `=destroy`*(t: var Task) {.inline, gcsafe.} =
+    ## Frees the resources allocated for a `Task`.
+    if t.args != nil:
+      if t.destroy != nil:
+        t.destroy(t.args)
+      deallocShared(t.args)
+
+proc invoke*(task: Task; res: pointer = nil) {.inline, gcsafe.} =
   ## Invokes the `task`.
   assert task.callback != nil
-  task.callback(task.args)
+  task.callback(task.args, res)
 
 template checkIsolate(scratchAssignList: seq[NimNode], procParam, scratchDotExpr: NimNode) =
   # block:
@@ -102,21 +110,38 @@ template addAllNode(assignParam: NimNode, procParam: NimNode) =
   tempAssignList.add newLetStmt(tempNode, newDotExpr(objTemp, formalParams[i][0]))
   scratchRecList.add newIdentDefs(newIdentNode(formalParams[i][0].strVal), assignParam)
 
+proc analyseRootSym(s: NimNode): NimNode =
+  result = s
+  while true:
+    case result.kind
+    of nnkBracketExpr, nnkDerefExpr, nnkHiddenDeref,
+        nnkAddr, nnkHiddenAddr,
+        nnkObjDownConv, nnkObjUpConv:
+      result = result[0]
+    of nnkDotExpr, nnkCheckedFieldExpr, nnkHiddenStdConv, nnkHiddenSubConv:
+      result = result[1]
+    else:
+      break
+
 macro toTask*(e: typed{nkCall | nkInfix | nkPrefix | nkPostfix | nkCommand | nkCallStrLit}): Task =
   ## Converts the call and its arguments to `Task`.
-  runnableExamples("--gc:orc"):
+  runnableExamples:
     proc hello(a: int) = echo a
 
     let b = toTask hello(13)
     assert b is Task
 
-  doAssert getTypeInst(e).typeKind == ntyVoid
+  let retType = getTypeInst(e)
+  let returnsVoid = retType.typeKind == ntyVoid
+
+  let rootSym = analyseRootSym(e[0])
+  expectKind rootSym, nnkSym
 
   when compileOption("threads"):
-    if not isGcSafe(e[0]):
+    if not isGcSafe(rootSym):
       error("'toTask' takes a GC safe call expression", e)
 
-  if hasClosure(e[0]):
+  if hasClosure(rootSym):
     error("closure call is not allowed", e)
 
   if e.len > 1:
@@ -165,7 +190,7 @@ macro toTask*(e: typed{nkCall | nkInfix | nkPrefix | nkPostfix | nkCommand | nkC
         # passing by static parameters
         # so we pass them directly instead of passing by scratchObj
         callNode.add nnkExprEqExpr.newTree(formalParams[i][0], e[i])
-      of nnkSym, nnkPtrTy:
+      of nnkSym, nnkPtrTy, nnkProcTy, nnkTupleConstr:
         addAllNode(param, e[i])
       of nnkCharLit..nnkNilLit:
         callNode.add nnkExprEqExpr.newTree(formalParams[i][0], e[i])
@@ -187,40 +212,43 @@ macro toTask*(e: typed{nkCall | nkInfix | nkPrefix | nkPostfix | nkCommand | nkC
 
 
     let scratchObjPtrType = quote do:
-      cast[ptr `scratchObjType`](c_calloc(csize_t 1, csize_t sizeof(`scratchObjType`)))
-
-    let scratchLetSection = newLetStmt(
-      scratchIdent,
-      scratchObjPtrType
-    )
+      cast[ptr `scratchObjType`](allocShared0(sizeof(`scratchObjType`)))
 
-    let scratchCheck = quote do:
-      if `scratchIdent`.isNil:
-        raise newException(OutOfMemDefect, "Could not allocate memory")
+    let scratchLetSection = newLetStmt(scratchIdent, scratchObjPtrType)
 
     var stmtList = newStmtList()
     stmtList.add(scratchObj)
     stmtList.add(scratchLetSection)
-    stmtList.add(scratchCheck)
     stmtList.add(nnkBlockStmt.newTree(newEmptyNode(), newStmtList(scratchAssignList)))
 
     var functionStmtList = newStmtList()
     let funcCall = newCall(e[0], callNode)
     functionStmtList.add tempAssignList
-    functionStmtList.add funcCall
 
-    let funcName = genSym(nskProc, e[0].strVal)
+    let funcName = genSym(nskProc, rootSym.strVal)
     let destroyName = genSym(nskProc, "destroyScratch")
     let objTemp2 = genSym(ident = "obj")
     let tempNode = quote("@") do:
         `=destroy`(@objTemp2[])
 
+    var funcDecl: NimNode
+    if returnsVoid:
+      funcDecl = quote do:
+        proc `funcName`(args, res: pointer) {.gcsafe, nimcall.} =
+          let `objTemp` = cast[ptr `scratchObjType`](args)
+          `functionStmtList`
+          `funcCall`
+    else:
+      funcDecl = quote do:
+        proc `funcName`(args, res: pointer) {.gcsafe, nimcall.} =
+          let `objTemp` = cast[ptr `scratchObjType`](args)
+          `functionStmtList`
+          cast[ptr `retType`](res)[] = `funcCall`
+
     result = quote do:
       `stmtList`
 
-      proc `funcName`(args: pointer) {.gcsafe, nimcall.} =
-        let `objTemp` = cast[ptr `scratchObjType`](args)
-        `functionStmtList`
+      `funcDecl`
 
       proc `destroyName`(args: pointer) {.gcsafe, nimcall.} =
         let `objTemp2` = cast[ptr `scratchObjType`](args)
@@ -229,18 +257,26 @@ macro toTask*(e: typed{nkCall | nkInfix | nkPrefix | nkPostfix | nkCommand | nkC
       Task(callback: `funcName`, args: `scratchIdent`, destroy: `destroyName`)
   else:
     let funcCall = newCall(e[0])
-    let funcName = genSym(nskProc, e[0].strVal)
+    let funcName = genSym(nskProc, rootSym.strVal)
 
-    result = quote do:
-      proc `funcName`(args: pointer) {.gcsafe, nimcall.} =
-        `funcCall`
+    if returnsVoid:
+      result = quote do:
+        proc `funcName`(args, res: pointer) {.gcsafe, nimcall.} =
+          `funcCall`
+
+        Task(callback: `funcName`, args: nil)
+    else:
+      result = quote do:
+        proc `funcName`(args, res: pointer) {.gcsafe, nimcall.} =
+          cast[ptr `retType`](res)[] = `funcCall`
+
+        Task(callback: `funcName`, args: nil)
 
-      Task(callback: `funcName`, args: nil)
 
   when defined(nimTasksDebug):
     echo result.repr
 
-runnableExamples("--gc:orc"):
+runnableExamples:
   block:
     var num = 0
     proc hello(a: int) = inc num, a
diff --git a/lib/std/tempfiles.nim b/lib/std/tempfiles.nim
index ee42f8a5c..539305bde 100644
--- a/lib/std/tempfiles.nim
+++ b/lib/std/tempfiles.nim
@@ -17,7 +17,7 @@ See also:
 * `mkstemp` (posix), refs https://man7.org/linux/man-pages/man3/mkstemp.3.html
 ]#
 
-import os, random
+import std / [os, random]
 
 when defined(nimPreviewSlimSystem):
   import std/syncio
@@ -29,7 +29,9 @@ const
 
 
 when defined(windows):
-  import winlean
+  import std/winlean
+  when defined(nimPreviewSlimSystem):
+    import std/widestrs
 
   var O_RDWR {.importc: "_O_RDWR", header: "<fcntl.h>".}: cint
 
@@ -44,7 +46,7 @@ when defined(windows):
   proc close_osfandle(fd: cint): cint {.
     importc: "_close", header: "<io.h>".}
 else:
-  import posix
+  import std/posix
 
   proc c_fdopen(
     filehandle: cint,
diff --git a/lib/std/time_t.nim b/lib/std/time_t.nim
index 7fb6e6d46..de051b135 100644
--- a/lib/std/time_t.nim
+++ b/lib/std/time_t.nim
@@ -14,10 +14,10 @@ when defined(nimdoc):
       ## Wrapper for `time_t`. On posix, this is an alias to `posix.Time`.
 elif defined(windows):
   when defined(i386) and defined(gcc):
-    type Time* {.importc: "time_t", header: "<time.h>".} = distinct int32
+    type Time* {.importc: "time_t", header: "<time.h>".} = distinct clong
   else:
     # newest version of Visual C++ defines time_t to be of 64 bits
     type Time* {.importc: "time_t", header: "<time.h>".} = distinct int64
 elif defined(posix):
-  import posix
+  import std/posix
   export posix.Time
\ No newline at end of file
diff --git a/lib/std/typedthreads.nim b/lib/std/typedthreads.nim
new file mode 100644
index 000000000..7b0b81968
--- /dev/null
+++ b/lib/std/typedthreads.nim
@@ -0,0 +1,305 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2012 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+##[
+Thread support for Nim. Threads allow multiple functions to execute concurrently.
+ 
+In Nim, threads are a low-level construct and using a library like `malebolgia`, `taskpools` or `weave` is recommended.
+ 
+When creating a thread, you can pass arguments to it. As Nim's garbage collector does not use atomic references, sharing
+`ref` and other variables managed by the garbage collector between threads is not supported.
+Use global variables to do so, or pointers.
+ 
+Memory allocated using [`sharedAlloc`](./system.html#allocShared.t%2CNatural) can be used and shared between threads.
+
+To communicate between threads, consider using [channels](./system.html#Channel)
+
+Examples
+========
+
+```Nim
+import std/locks
+
+var
+  thr: array[0..4, Thread[tuple[a,b: int]]]
+  L: Lock
+
+proc threadFunc(interval: tuple[a,b: int]) {.thread.} =
+  for i in interval.a..interval.b:
+    acquire(L) # lock stdout
+    echo i
+    release(L)
+
+initLock(L)
+
+for i in 0..high(thr):
+  createThread(thr[i], threadFunc, (i*10, i*10+5))
+joinThreads(thr)
+
+deinitLock(L)
+```
+ 
+When using a memory management strategy that supports shared heaps like `arc` or `boehm`,
+you can pass pointer to threads and share memory between them, but the memory must outlive the thread.
+The default memory management strategy, `orc`, supports this.
+The example below is **not valid** for memory management strategies that use local heaps like `refc`!
+
+```Nim
+import locks
+ 
+var l: Lock
+ 
+proc threadFunc(obj: ptr seq[int]) {.thread.} =
+  withLock l:
+    for i in 0..<100:
+      obj[].add(obj[].len * obj[].len)
+ 
+proc threadHandler() =
+  var thr: array[0..4, Thread[ptr seq[int]]]
+  var s = newSeq[int]()
+    
+  for i in 0..high(thr):
+    createThread(thr[i], threadFunc, s.addr)
+  joinThreads(thr)
+  echo s
+ 
+initLock(l)
+threadHandler()
+deinitLock(l)
+```
+]##
+
+
+import std/private/[threadtypes]
+export Thread
+
+import system/ansi_c
+
+when defined(nimPreviewSlimSystem):
+  import std/assertions
+
+when defined(genode):
+  import genode/env
+
+when hostOS == "any":
+  {.error: "Threads not implemented for os:any. Please compile with --threads:off.".}
+
+when hasAllocStack or defined(zephyr) or defined(freertos) or defined(nuttx) or
+    defined(cpu16) or defined(cpu8):
+  const
+    nimThreadStackSize {.intdefine.} = 8192
+    nimThreadStackGuard {.intdefine.} = 128
+
+    StackGuardSize = nimThreadStackGuard
+    ThreadStackSize = nimThreadStackSize - nimThreadStackGuard
+else:
+  const
+    StackGuardSize = 4096
+    ThreadStackMask =
+      when defined(genode):
+        1024*64*sizeof(int)-1
+      else:
+        1024*256*sizeof(int)-1
+
+    ThreadStackSize = ThreadStackMask+1 - StackGuardSize
+
+
+when defined(gcDestructors):
+  proc allocThreadStorage(size: int): pointer =
+    result = c_malloc(csize_t size)
+    zeroMem(result, size)
+else:
+  template allocThreadStorage(size: untyped): untyped = allocShared0(size)
+
+#const globalsSlot = ThreadVarSlot(0)
+#sysAssert checkSlot.int == globalsSlot.int
+
+# Zephyr doesn't include this properly without some help
+when defined(zephyr):
+  {.emit: """/*INCLUDESECTION*/
+  #include <pthread.h>
+  """.}
+
+
+# We jump through some hops here to ensure that Nim thread procs can have
+# the Nim calling convention. This is needed because thread procs are
+# ``stdcall`` on Windows and ``noconv`` on UNIX. Alternative would be to just
+# use ``stdcall`` since it is mapped to ``noconv`` on UNIX anyway.
+
+
+
+{.push stack_trace:off.}
+when defined(windows):
+  proc threadProcWrapper[TArg](closure: pointer): int32 {.stdcall.} =
+    nimThreadProcWrapperBody(closure)
+    # implicitly return 0
+elif defined(genode):
+  proc threadProcWrapper[TArg](closure: pointer) {.noconv.} =
+    nimThreadProcWrapperBody(closure)
+else:
+  proc threadProcWrapper[TArg](closure: pointer): pointer {.noconv.} =
+    nimThreadProcWrapperBody(closure)
+{.pop.}
+
+proc running*[TArg](t: Thread[TArg]): bool {.inline.} =
+  ## Returns true if `t` is running.
+  result = t.dataFn != nil
+
+proc handle*[TArg](t: Thread[TArg]): SysThread {.inline.} =
+  ## Returns the thread handle of `t`.
+  result = t.sys
+
+when hostOS == "windows":
+  const MAXIMUM_WAIT_OBJECTS = 64
+
+  proc joinThread*[TArg](t: Thread[TArg]) {.inline.} =
+    ## Waits for the thread `t` to finish.
+    discard waitForSingleObject(t.sys, -1'i32)
+
+  proc joinThreads*[TArg](t: varargs[Thread[TArg]]) =
+    ## Waits for every thread in `t` to finish.
+    var a: array[MAXIMUM_WAIT_OBJECTS, SysThread]
+    var k = 0
+    while k < len(t):
+      var count = min(len(t) - k, MAXIMUM_WAIT_OBJECTS)
+      for i in 0..(count - 1): a[i] = t[i + k].sys
+      discard waitForMultipleObjects(int32(count),
+                                     cast[ptr SysThread](addr(a)), 1, -1)
+      inc(k, MAXIMUM_WAIT_OBJECTS)
+
+elif defined(genode):
+  proc joinThread*[TArg](t: Thread[TArg]) {.importcpp.}
+    ## Waits for the thread `t` to finish.
+
+  proc joinThreads*[TArg](t: varargs[Thread[TArg]]) =
+    ## Waits for every thread in `t` to finish.
+    for i in 0..t.high: joinThread(t[i])
+
+else:
+  proc joinThread*[TArg](t: Thread[TArg]) {.inline.} =
+    ## Waits for the thread `t` to finish.
+    discard pthread_join(t.sys, nil)
+
+  proc joinThreads*[TArg](t: varargs[Thread[TArg]]) =
+    ## Waits for every thread in `t` to finish.
+    for i in 0..t.high: joinThread(t[i])
+
+when false:
+  # XXX a thread should really release its heap here somehow:
+  proc destroyThread*[TArg](t: var Thread[TArg]) =
+    ## Forces the thread `t` to terminate. This is potentially dangerous if
+    ## you don't have full control over `t` and its acquired resources.
+    when hostOS == "windows":
+      discard TerminateThread(t.sys, 1'i32)
+    else:
+      discard pthread_cancel(t.sys)
+    when declared(registerThread): unregisterThread(addr(t))
+    t.dataFn = nil
+    ## if thread `t` already exited, `t.core` will be `null`.
+    if not isNil(t.core):
+      deallocThreadStorage(t.core)
+      t.core = nil
+
+when hostOS == "windows":
+  proc createThread*[TArg](t: var Thread[TArg],
+                           tp: proc (arg: TArg) {.thread, nimcall.},
+                           param: TArg) =
+    ## Creates a new thread `t` and starts its execution.
+    ##
+    ## Entry point is the proc `tp`.
+    ## `param` is passed to `tp`. `TArg` can be `void` if you
+    ## don't need to pass any data to the thread.
+    t.core = cast[PGcThread](allocThreadStorage(sizeof(GcThread)))
+
+    when TArg isnot void: t.data = param
+    t.dataFn = tp
+    when hasSharedHeap: t.core.stackSize = ThreadStackSize
+    var dummyThreadId: int32
+    t.sys = createThread(nil, ThreadStackSize, threadProcWrapper[TArg],
+                         addr(t), 0'i32, dummyThreadId)
+    if t.sys <= 0:
+      raise newException(ResourceExhaustedError, "cannot create thread")
+
+  proc pinToCpu*[Arg](t: var Thread[Arg]; cpu: Natural) =
+    ## Pins a thread to a `CPU`:idx:.
+    ##
+    ## In other words sets a thread's `affinity`:idx:.
+    ## If you don't know what this means, you shouldn't use this proc.
+    setThreadAffinityMask(t.sys, uint(1 shl cpu))
+
+elif defined(genode):
+  var affinityOffset: cuint = 1
+    ## CPU affinity offset for next thread, safe to roll-over.
+
+  proc createThread*[TArg](t: var Thread[TArg],
+                           tp: proc (arg: TArg) {.thread, nimcall.},
+                           param: TArg) =
+    t.core = cast[PGcThread](allocThreadStorage(sizeof(GcThread)))
+
+    when TArg isnot void: t.data = param
+    t.dataFn = tp
+    when hasSharedHeap: t.stackSize = ThreadStackSize
+    t.sys.initThread(
+      runtimeEnv,
+      ThreadStackSize.culonglong,
+      threadProcWrapper[TArg], addr(t), affinityOffset)
+    inc affinityOffset
+
+  proc pinToCpu*[Arg](t: var Thread[Arg]; cpu: Natural) =
+    {.hint: "cannot change Genode thread CPU affinity after initialization".}
+    discard
+
+else:
+  proc createThread*[TArg](t: var Thread[TArg],
+                           tp: proc (arg: TArg) {.thread, nimcall.},
+                           param: TArg) =
+    ## Creates a new thread `t` and starts its execution.
+    ##
+    ## Entry point is the proc `tp`. `param` is passed to `tp`.
+    ## `TArg` can be `void` if you
+    ## don't need to pass any data to the thread.
+    t.core = cast[PGcThread](allocThreadStorage(sizeof(GcThread)))
+
+    when TArg isnot void: t.data = param
+    t.dataFn = tp
+    when hasSharedHeap: t.core.stackSize = ThreadStackSize
+    var a {.noinit.}: Pthread_attr
+    doAssert pthread_attr_init(a) == 0
+    when hasAllocStack:
+      var
+        rawstk = allocThreadStorage(ThreadStackSize + StackGuardSize)
+        stk = cast[pointer](cast[uint](rawstk) + StackGuardSize)
+      let setstacksizeResult = pthread_attr_setstack(addr a, stk, ThreadStackSize)
+      t.rawStack = rawstk
+    else:
+      let setstacksizeResult = pthread_attr_setstacksize(a, ThreadStackSize)
+
+    when not defined(ios):
+      # This fails on iOS
+      doAssert(setstacksizeResult == 0)
+    if pthread_create(t.sys, a, threadProcWrapper[TArg], addr(t)) != 0:
+      raise newException(ResourceExhaustedError, "cannot create thread")
+    doAssert pthread_attr_destroy(a) == 0
+
+  proc pinToCpu*[Arg](t: var Thread[Arg]; cpu: Natural) =
+    ## Pins a thread to a `CPU`:idx:.
+    ##
+    ## In other words sets a thread's `affinity`:idx:.
+    ## If you don't know what this means, you shouldn't use this proc.
+    when not defined(macosx):
+      var s {.noinit.}: CpuSet
+      cpusetZero(s)
+      cpusetIncl(cpu.cint, s)
+      setAffinity(t.sys, csize_t(sizeof(s)), s)
+
+proc createThread*(t: var Thread[void], tp: proc () {.thread, nimcall.}) =
+  createThread[void](t, tp)
+
+when not defined(gcOrc):
+  include system/threadids
diff --git a/lib/std/varints.nim b/lib/std/varints.nim
index 0d18b9069..32fe2fffb 100644
--- a/lib/std/varints.nim
+++ b/lib/std/varints.nim
@@ -82,29 +82,29 @@ proc writeVu64*(z: var openArray[byte], x: uint64): int =
       z[3] = cast[uint8](y)
       return 4
     z[0] = 251
-    varintWrite32(toOpenArray(z, 1, z.high-1), y)
+    varintWrite32(toOpenArray(z, 1, 4), y)
     return 5
   if w <= 255:
     z[0] = 252
     z[1] = cast[uint8](w)
-    varintWrite32(toOpenArray(z, 2, z.high-2), y)
+    varintWrite32(toOpenArray(z, 2, 5), y)
     return 6
   if w <= 65535:
     z[0] = 253
     z[1] = cast[uint8](w shr 8)
     z[2] = cast[uint8](w)
-    varintWrite32(toOpenArray(z, 3, z.high-3), y)
+    varintWrite32(toOpenArray(z, 3, 6), y)
     return 7
   if w <= 16777215:
     z[0] = 254
     z[1] = cast[uint8](w shr 16)
     z[2] = cast[uint8](w shr 8)
     z[3] = cast[uint8](w)
-    varintWrite32(toOpenArray(z, 4, z.high-4), y)
+    varintWrite32(toOpenArray(z, 4, 7), y)
     return 8
   z[0] = 255
-  varintWrite32(toOpenArray(z, 1, z.high-1), w)
-  varintWrite32(toOpenArray(z, 5, z.high-5), y)
+  varintWrite32(toOpenArray(z, 1, 4), w)
+  varintWrite32(toOpenArray(z, 5, 8), y)
   return 9
 
 proc sar(a, b: int64): int64 =
diff --git a/lib/std/widestrs.nim b/lib/std/widestrs.nim
new file mode 100644
index 000000000..2ddf80d14
--- /dev/null
+++ b/lib/std/widestrs.nim
@@ -0,0 +1,239 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2012 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+## Nim support for C/C++'s `wide strings`:idx:.
+
+#when not declared(ThisIsSystem):
+#  {.error: "You must not import this module explicitly".}
+
+type
+  Utf16Char* = distinct int16
+
+when not (defined(cpu16) or defined(cpu8)):
+  when defined(nimv2):
+
+    type
+      WideCString* = ptr UncheckedArray[Utf16Char]
+
+      WideCStringObj* = object
+        bytes: int
+        data: WideCString
+
+    const arcLike = defined(gcArc) or defined(gcAtomicArc) or defined(gcOrc)
+    when defined(nimAllowNonVarDestructor) and arcLike:
+      proc `=destroy`(a: WideCStringObj) =
+        if a.data != nil:
+          when compileOption("threads"):
+            deallocShared(a.data)
+          else:
+            dealloc(a.data)
+    else:
+      proc `=destroy`(a: var WideCStringObj) =
+        if a.data != nil:
+          when compileOption("threads"):
+            deallocShared(a.data)
+          else:
+            dealloc(a.data)
+
+    proc `=copy`(a: var WideCStringObj; b: WideCStringObj) {.error.}
+
+    proc `=sink`(a: var WideCStringObj; b: WideCStringObj) =
+      a.bytes = b.bytes
+      a.data = b.data
+
+    proc createWide(a: var WideCStringObj; bytes: int) =
+      a.bytes = bytes
+      when compileOption("threads"):
+        a.data = cast[typeof(a.data)](allocShared0(bytes))
+      else:
+        a.data = cast[typeof(a.data)](alloc0(bytes))
+
+    template `[]`*(a: WideCStringObj; idx: int): Utf16Char = a.data[idx]
+    template `[]=`*(a: WideCStringObj; idx: int; val: Utf16Char) = a.data[idx] = val
+
+    template nullWide(): untyped = WideCStringObj(bytes: 0, data: nil)
+
+    converter toWideCString*(x: WideCStringObj): WideCString {.inline.} =
+      result = x.data
+
+  else:
+    template nullWide(): untyped = nil
+
+    type
+      WideCString* = ref UncheckedArray[Utf16Char]
+      WideCStringObj* = WideCString
+
+    template createWide(a; L) =
+      unsafeNew(a, L)
+
+  proc ord(arg: Utf16Char): int = int(cast[uint16](arg))
+
+  proc len*(w: WideCString): int =
+    ## returns the length of a widestring. This traverses the whole string to
+    ## find the binary zero end marker!
+    result = 0
+    while int16(w[result]) != 0'i16: inc result
+
+  const
+    UNI_REPLACEMENT_CHAR = Utf16Char(0xFFFD'i16)
+    UNI_MAX_BMP = 0x0000FFFF
+    UNI_MAX_UTF16 = 0x0010FFFF
+    # UNI_MAX_UTF32 = 0x7FFFFFFF
+    # UNI_MAX_LEGAL_UTF32 = 0x0010FFFF
+
+    halfShift = 10
+    halfBase = 0x0010000
+    halfMask = 0x3FF
+
+    UNI_SUR_HIGH_START = 0xD800
+    UNI_SUR_HIGH_END = 0xDBFF
+    UNI_SUR_LOW_START = 0xDC00
+    UNI_SUR_LOW_END = 0xDFFF
+    UNI_REPL = 0xFFFD
+
+  template ones(n: untyped): untyped = ((1 shl n)-1)
+
+  template fastRuneAt(s: cstring, i, L: int, result: untyped, doInc = true) =
+    ## Returns the unicode character `s[i]` in `result`. If `doInc == true`
+    ## `i` is incremented by the number of bytes that have been processed.
+    bind ones
+
+    if ord(s[i]) <= 127:
+      result = ord(s[i])
+      when doInc: inc(i)
+    elif ord(s[i]) shr 5 == 0b110:
+      #assert(ord(s[i+1]) shr 6 == 0b10)
+      if i <= L - 2:
+        result = (ord(s[i]) and (ones(5))) shl 6 or (ord(s[i+1]) and ones(6))
+        when doInc: inc(i, 2)
+      else:
+        result = UNI_REPL
+        when doInc: inc(i)
+    elif ord(s[i]) shr 4 == 0b1110:
+      if i <= L - 3:
+        #assert(ord(s[i+1]) shr 6 == 0b10)
+        #assert(ord(s[i+2]) shr 6 == 0b10)
+        result = (ord(s[i]) and ones(4)) shl 12 or
+                (ord(s[i+1]) and ones(6)) shl 6 or
+                (ord(s[i+2]) and ones(6))
+        when doInc: inc(i, 3)
+      else:
+        result = UNI_REPL
+        when doInc: inc(i)
+    elif ord(s[i]) shr 3 == 0b11110:
+      if i <= L - 4:
+        #assert(ord(s[i+1]) shr 6 == 0b10)
+        #assert(ord(s[i+2]) shr 6 == 0b10)
+        #assert(ord(s[i+3]) shr 6 == 0b10)
+        result = (ord(s[i]) and ones(3)) shl 18 or
+                (ord(s[i+1]) and ones(6)) shl 12 or
+                (ord(s[i+2]) and ones(6)) shl 6 or
+                (ord(s[i+3]) and ones(6))
+        when doInc: inc(i, 4)
+      else:
+        result = UNI_REPL
+        when doInc: inc(i)
+    else:
+      result = 0xFFFD
+      when doInc: inc(i)
+
+  iterator runes(s: cstring, L: int): int =
+    var
+      i = 0
+      result: int
+    while i < L:
+      fastRuneAt(s, i, L, result, true)
+      yield result
+
+  proc newWideCString*(size: int): WideCStringObj =
+    createWide(result, size * 2 + 2)
+
+  proc newWideCString*(source: cstring, L: int): WideCStringObj =
+    ## Warning:: `source` needs to be preallocated with the length `L`
+    createWide(result, L * 2 + 2)
+    var d = 0
+    for ch in runes(source, L):
+
+      if ch <= UNI_MAX_BMP:
+        if ch >= UNI_SUR_HIGH_START and ch <= UNI_SUR_LOW_END:
+          result[d] = UNI_REPLACEMENT_CHAR
+        else:
+          result[d] = cast[Utf16Char](uint16(ch))
+      elif ch > UNI_MAX_UTF16:
+        result[d] = UNI_REPLACEMENT_CHAR
+      else:
+        let ch = ch - halfBase
+        result[d] = cast[Utf16Char](uint16((ch shr halfShift) + UNI_SUR_HIGH_START))
+        inc d
+        result[d] = cast[Utf16Char](uint16((ch and halfMask) + UNI_SUR_LOW_START))
+      inc d
+    result[d] = Utf16Char(0)
+
+  proc newWideCString*(s: cstring): WideCStringObj =
+    if s.isNil: return nullWide
+
+    result = newWideCString(s, s.len)
+
+  proc newWideCString*(s: string): WideCStringObj =
+    result = newWideCString(cstring s, s.len)
+
+  proc `$`*(w: WideCString, estimate: int, replacement: int = 0xFFFD): string =
+    result = newStringOfCap(estimate + estimate shr 2)
+
+    var i = 0
+    while w[i].int16 != 0'i16:
+      var ch = ord(w[i])
+      inc i
+      if ch >= UNI_SUR_HIGH_START and ch <= UNI_SUR_HIGH_END:
+        # If the 16 bits following the high surrogate are in the source buffer...
+        let ch2 = ord(w[i])
+
+        # If it's a low surrogate, convert to UTF32:
+        if ch2 >= UNI_SUR_LOW_START and ch2 <= UNI_SUR_LOW_END:
+          ch = (((ch and halfMask) shl halfShift) + (ch2 and halfMask)) + halfBase
+          inc i
+        else:
+          #invalid UTF-16
+          ch = replacement
+      elif ch >= UNI_SUR_LOW_START and ch <= UNI_SUR_LOW_END:
+        #invalid UTF-16
+        ch = replacement
+
+      if ch < 0x80:
+        result.add chr(ch)
+      elif ch < 0x800:
+        result.add chr((ch shr 6) or 0xc0)
+        result.add chr((ch and 0x3f) or 0x80)
+      elif ch < 0x10000:
+        result.add chr((ch shr 12) or 0xe0)
+        result.add chr(((ch shr 6) and 0x3f) or 0x80)
+        result.add chr((ch and 0x3f) or 0x80)
+      elif ch <= 0x10FFFF:
+        result.add chr((ch shr 18) or 0xf0)
+        result.add chr(((ch shr 12) and 0x3f) or 0x80)
+        result.add chr(((ch shr 6) and 0x3f) or 0x80)
+        result.add chr((ch and 0x3f) or 0x80)
+      else:
+        # replacement char(in case user give very large number):
+        result.add chr(0xFFFD shr 12 or 0b1110_0000)
+        result.add chr(0xFFFD shr 6 and ones(6) or 0b10_0000_00)
+        result.add chr(0xFFFD and ones(6) or 0b10_0000_00)
+
+  proc `$`*(s: WideCString): string =
+    result = s $ 80
+
+  when defined(nimv2):
+    proc `$`*(s: WideCStringObj, estimate: int, replacement: int = 0xFFFD): string =
+      `$`(s.data, estimate, replacement)
+
+    proc `$`*(s: WideCStringObj): string =
+      $(s.data)
+
+    proc len*(w: WideCStringObj): int {.inline.} =
+      len(w.data)
diff --git a/lib/std/with.nim b/lib/std/with.nim
index c7338b4e4..c2eaa4bef 100644
--- a/lib/std/with.nim
+++ b/lib/std/with.nim
@@ -14,7 +14,7 @@
 ##
 ## **Since:** version 1.2.
 
-import macros, private / underscored_calls
+import std/[macros, private / underscored_calls]
 
 macro with*(arg: typed; calls: varargs[untyped]): untyped =
   ## This macro provides `chaining`:idx: of function calls.
@@ -35,5 +35,14 @@ macro with*(arg: typed; calls: varargs[untyped]): untyped =
       -= 5
     doAssert a == 43
 
+    # Nesting works for object types too!
+    var foo = (bar: 1, qux: (baz: 2))
+    with foo:
+      bar = 2
+      with qux:
+        baz = 3
+    doAssert foo.bar == 2
+    doAssert foo.qux.baz == 3
+
   result = newNimNode(nnkStmtList, arg)
   underscoredCalls(result, calls, arg)
diff --git a/lib/std/wordwrap.nim b/lib/std/wordwrap.nim
index 7dcfc7f59..9333f880b 100644
--- a/lib/std/wordwrap.nim
+++ b/lib/std/wordwrap.nim
@@ -9,7 +9,7 @@
 
 ## This module contains an algorithm to wordwrap a Unicode string.
 
-import strutils, unicode
+import std/[strutils, unicode]
 
 proc olen(s: string; start, lastExclusive: int): int =
   var i = start
diff --git a/lib/std/wrapnils.nim b/lib/std/wrapnils.nim
index facba85fa..0b75c270e 100644
--- a/lib/std/wrapnils.nim
+++ b/lib/std/wrapnils.nim
@@ -13,7 +13,7 @@ consider handling indexing operations, eg:
 doAssert ?.default(seq[int])[3] == default(int)
 ]#
 
-import macros
+import std/macros
 
 runnableExamples:
   type Foo = ref object
@@ -60,7 +60,7 @@ proc finalize(n: NimNode, lhs: NimNode, level: int): NimNode =
   else:
     result = quote: (let `lhs` = `n`)
 
-proc process(n: NimNode, lhs: NimNode, level: int): NimNode =
+proc process(n: NimNode, lhs: NimNode, label: NimNode, level: int): NimNode =
   var n = n.copyNimTree
   var it = n
   let addr2 = bindSym"addr"
@@ -78,7 +78,7 @@ proc process(n: NimNode, lhs: NimNode, level: int): NimNode =
       let okSet = check[1]
       let kind1 = check[2]
       let tmp = genSym(nskLet, "tmpCase")
-      let body = process(objRef, tmp, level + 1)
+      let body = process(objRef, tmp, label, level + 1)
       let tmp3 = nnkDerefExpr.newTree(tmp)
       it[0][0] = tmp3
       let dot2 = nnkDotExpr.newTree(@[tmp, dot[1]])
@@ -87,17 +87,17 @@ proc process(n: NimNode, lhs: NimNode, level: int): NimNode =
       let assgn = finalize(n, lhs, level)
       result = quote do:
         `body`
-        if `tmp3`.`kind1` notin `okSet`: break
+        if `tmp3`.`kind1` notin `okSet`: break `label`
         `assgn`
       break
     elif it.kind in {nnkHiddenDeref, nnkDerefExpr}:
       let tmp = genSym(nskLet, "tmp")
-      let body = process(it[0], tmp, level + 1)
+      let body = process(it[0], tmp, label, level + 1)
       it[0] = tmp
       let assgn = finalize(n, lhs, level)
       result = quote do:
         `body`
-        if `tmp` == nil: break
+        if `tmp` == nil: break `label`
         `assgn`
       break
     elif it.kind == nnkCall: # consider extending to `nnkCallKinds`
@@ -113,15 +113,16 @@ macro `?.`*(a: typed): auto =
   ## presence of intermediate nil pointers/references, in which case a default
   ## value is produced.
   let lhs = genSym(nskVar, "lhs")
-  let body = process(a, lhs, 0)
+  let label = genSym(nskLabel, "label")
+  let body = process(a, lhs, label, 0)
   result = quote do:
     var `lhs`: type(`a`)
-    block:
+    block `label`:
       `body`
     `lhs`
 
 # the code below is not needed for `?.`
-from options import Option, isSome, get, option, unsafeGet, UnpackDefect
+from std/options import Option, isSome, get, option, unsafeGet, UnpackDefect
 
 macro `??.`*(a: typed): Option =
   ## Same as `?.` but returns an `Option`.
@@ -144,10 +145,11 @@ macro `??.`*(a: typed): Option =
 
   let lhs = genSym(nskVar, "lhs")
   let lhs2 = genSym(nskVar, "lhs")
-  let body = process(a, lhs2, 0)
+  let label = genSym(nskLabel, "label")
+  let body = process(a, lhs2, label, 0)
   result = quote do:
     var `lhs`: Option[type(`a`)]
-    block:
+    block `label`:
       var `lhs2`: type(`a`)
       `body`
       `lhs` = option(`lhs2`)