3 files changed, 52 insertions, 21 deletions
diff --git a/lib/system/gc_common.nim b/lib/system/gc_common.nim
index 269514ceb..6ab6bd920 100644
--- a/lib/system/gc_common.nim
+++ b/lib/system/gc_common.nim
@@ -128,13 +128,7 @@ iterator items(stack: ptr GcStack): ptr GcStack =
     yield s
     s = s.next
 
-# There will be problems with GC in foreign threads if `threads` option is off or TLS emulation is enabled
-const allowForeignThreadGc = compileOption("threads") and not compileOption("tlsEmulation")
-
-when allowForeignThreadGc:
-  var
-    localGcInitialized {.rtlThreadVar.}: bool
-
+when declared(threadType):
   proc setupForeignThreadGc*() {.gcsafe.} =
     ## Call this if you registered a callback that will be run from a thread not
     ## under your control. This has a cheap thread-local guard, so the GC for
@@ -143,16 +137,33 @@ when allowForeignThreadGc:
     ##
     ## This function is available only when ``--threads:on`` and ``--tlsEmulation:off``
     ## switches are used
-    if not localGcInitialized:
-      localGcInitialized = true
+    if threadType == ThreadType.None:
       initAllocator()
       var stackTop {.volatile.}: pointer
       setStackBottom(addr(stackTop))
       initGC()
+      threadType = ThreadType.ForeignThread
+
+  proc tearDownForeignThreadGc*() {.gcsafe.} =
+    ## Call this to tear down the GC, previously initialized by ``setupForeignThreadGc``.
+    ## If GC has not been previously initialized, or has already been torn down, the
+    ## call does nothing.
+    ##
+    ## This function is available only when ``--threads:on`` and ``--tlsEmulation:off``
+    ## switches are used
+    if threadType != ThreadType.ForeignThread:
+      return
+    when declared(deallocOsPages): deallocOsPages()
+    threadType = ThreadType.None
+    when declared(gch): zeroMem(addr gch, sizeof(gch))
+
 else:
   template setupForeignThreadGc*() =
     {.error: "setupForeignThreadGc is available only when ``--threads:on`` and ``--tlsEmulation:off`` are used".}
 
+  template tearDownForeignThreadGc*() =
+    {.error: "tearDownForeignThreadGc is available only when ``--threads:on`` and ``--tlsEmulation:off`` are used".}
+
 # ----------------- stack management --------------------------------------
 #  inspired from Smart Eiffel
 
diff --git a/lib/system/sysio.nim b/lib/system/sysio.nim
index 9f4944eb0..7444661e3 100644
--- a/lib/system/sysio.nim
+++ b/lib/system/sysio.nim
@@ -67,7 +67,7 @@ proc checkErr(f: File) =
 {.push stackTrace:off, profiler:off.}
 proc readBuffer(f: File, buffer: pointer, len: Natural): int =
   result = c_fread(buffer, 1, len, f)
-  checkErr(f)
+  if result != len: checkErr(f)
 
 proc readBytes(f: File, a: var openArray[int8|uint8], start, len: Natural): int =
   result = readBuffer(f, addr(a[start]), len)
@@ -118,8 +118,9 @@ const
 proc close*(f: File) = discard c_fclose(f)
 proc readChar(f: File): char =
   let x = c_fgetc(f)
-  if x == -1: raiseEOF()
-  checkErr(f)
+  if x < 0:
+    checkErr(f)
+    raiseEOF()
   result = char(x)
 
 proc flushFile*(f: File) = discard c_fflush(f)
@@ -140,7 +141,7 @@ proc readLine(f: File, line: var TaintedString): bool =
     # fgets doesn't append an \L
     c_memset(addr line.string[pos], '\L'.ord, sp)
     var fgetsSuccess = c_fgets(addr line.string[pos], sp, f) != nil
-    checkErr(f)
+    if not fgetsSuccess: checkErr(f)
     let m = c_memchr(addr line.string[pos], '\L'.ord, sp)
     if m != nil:
       # \l found: Could be our own or the one by fgets, in any case, we're done
@@ -170,21 +171,23 @@ proc readLine(f: File): TaintedString =
 
 proc write(f: File, i: int) =
   when sizeof(int) == 8:
-    c_fprintf(f, "%lld", i)
+    if c_fprintf(f, "%lld", i) < 0: checkErr(f)
   else:
-    c_fprintf(f, "%ld", i)
+    if c_fprintf(f, "%ld", i) < 0: checkErr(f)
 
 proc write(f: File, i: BiggestInt) =
   when sizeof(BiggestInt) == 8:
-    c_fprintf(f, "%lld", i)
+    if c_fprintf(f, "%lld", i) < 0: checkErr(f)
   else:
-    c_fprintf(f, "%ld", i)
+    if c_fprintf(f, "%ld", i) < 0: checkErr(f)
 
 proc write(f: File, b: bool) =
   if b: write(f, "true")
   else: write(f, "false")
-proc write(f: File, r: float32) = c_fprintf(f, "%g", r)
-proc write(f: File, r: BiggestFloat) = c_fprintf(f, "%g", r)
+proc write(f: File, r: float32) =
+  if c_fprintf(f, "%g", r) < 0: checkErr(f)
+proc write(f: File, r: BiggestFloat) =
+  if c_fprintf(f, "%g", r) < 0: checkErr(f)
 
 proc write(f: File, c: char) = discard c_putc(ord(c), f)
 proc write(f: File, a: varargs[string, `$`]) =
@@ -212,7 +215,10 @@ proc rawFileSize(file: File): int =
   discard c_fseek(file, clong(oldPos), 0)
 
 proc endOfFile(f: File): bool =
-  result = c_feof(f) != 0
+  var c = c_fgetc(f)
+  discard c_ungetc(c, f)
+  return c < 0'i32
+  #result = c_feof(f) != 0
 
 proc readAllFile(file: File, len: int): string =
   # We acquire the filesize beforehand and hope it doesn't change.
diff --git a/lib/system/threads.nim b/lib/system/threads.nim
index e8b34bf2e..6e58638e9 100644
--- a/lib/system/threads.nim
+++ b/lib/system/threads.nim
@@ -285,7 +285,19 @@ when useStackMaskHack:
 when not defined(useNimRtl):
   when not useStackMaskHack:
     #when not defined(createNimRtl): initStackBottom()
-    when declared(initGC): initGC()
+    when declared(initGC):
+      initGC()
+      when not emulatedThreadVars:
+        type ThreadType {.pure.} = enum
+          None = 0,
+          NimThread = 1,
+          ForeignThread = 2
+        var
+          threadType {.rtlThreadVar.}: ThreadType
+
+        threadType = ThreadType.NimThread
+
+
 
   when emulatedThreadVars:
     if nimThreadVarsSize() > sizeof(ThreadLocalStorage):
@@ -442,6 +454,8 @@ proc threadProcWrapStackFrame[TArg](thrd: ptr Thread[TArg]) =
       # init the GC for refc/markandsweep
       setStackBottom(addr(p))
       initGC()
+      when declared(threadType):
+        threadType = ThreadType.NimThread
     when declared(registerThread):
       thrd.stackBottom = addr(thrd)
       registerThread(thrd)