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-rw-r--r--lib/impure/re.nim8
-rw-r--r--lib/packages/docutils/rstast.nim4
-rw-r--r--lib/packages/docutils/rstgen.nim9
-rw-r--r--lib/pure/asyncfutures.nim4
-rw-r--r--lib/pure/asyncnet.nim4
-rw-r--r--lib/pure/collections/intsets.nim24
-rw-r--r--lib/pure/net.nim48
-rw-r--r--lib/pure/parseopt2.nim6
-rw-r--r--lib/pure/parsexml.nim10
-rw-r--r--lib/pure/pegs.nim2
-rw-r--r--lib/pure/streams.nim5
-rw-r--r--lib/pure/unittest.nim13
-rw-r--r--lib/pure/xmldom.nim24
-rw-r--r--lib/pure/xmldomparser.nim4
-rw-r--r--lib/system.nim21
15 files changed, 101 insertions, 85 deletions
diff --git a/lib/impure/re.nim b/lib/impure/re.nim
index 201c490f3..50a5441e8 100644
--- a/lib/impure/re.nim
+++ b/lib/impure/re.nim
@@ -113,7 +113,7 @@ proc matchOrFind(buf: cstring, pattern: Regex, matches: var openArray[string],
     var b = rawMatches[i * 2 + 1]
     if a >= 0'i32:
       matches[i-1] = bufSubstr(buf, int(a), int(b))
-    else: matches[i-1] = nil
+    else: matches[i-1] = ""
   return rawMatches[1] - rawMatches[0]
 
 proc findBounds*(buf: cstring, pattern: Regex, matches: var openArray[string],
@@ -133,7 +133,7 @@ proc findBounds*(buf: cstring, pattern: Regex, matches: var openArray[string],
     var a = rawMatches[i * 2]
     var b = rawMatches[i * 2 + 1]
     if a >= 0'i32: matches[i-1] = bufSubstr(buf, int(a), int(b))
-    else: matches[i-1] = nil
+    else: matches[i-1] = ""
   return (rawMatches[0].int, rawMatches[1].int - 1)
 
 proc findBounds*(s: string, pattern: Regex, matches: var openArray[string],
@@ -287,7 +287,7 @@ proc find*(buf: cstring, pattern: Regex, matches: var openArray[string],
     var a = rawMatches[i * 2]
     var b = rawMatches[i * 2 + 1]
     if a >= 0'i32: matches[i-1] = bufSubstr(buf, int(a), int(b))
-    else: matches[i-1] = nil
+    else: matches[i-1] = ""
   return rawMatches[0]
 
 proc find*(s: string, pattern: Regex, matches: var openArray[string],
@@ -456,8 +456,6 @@ proc replacef*(s: string, sub: Regex, by: string): string =
   while true:
     var match = findBounds(s, sub, caps, prev)
     if match.first < 0: break
-    assert result != nil
-    assert s != nil
     add(result, substr(s, prev, match.first-1))
     addf(result, by, caps)
     prev = match.last + 1
diff --git a/lib/packages/docutils/rstast.nim b/lib/packages/docutils/rstast.nim
index f3596b571..4a77b4f34 100644
--- a/lib/packages/docutils/rstast.nim
+++ b/lib/packages/docutils/rstast.nim
@@ -293,9 +293,9 @@ proc renderRstToJsonNode(node: PRstNode): JsonNode =
       (key: "kind", val: %($node.kind)),
       (key: "level", val: %BiggestInt(node.level))
      ]
-  if node.text != nil:
+  if node.text.len > 0:
     result.add("text", %node.text)
-  if node.sons != nil and len(node.sons) > 0:
+  if len(node.sons) > 0:
     var accm = newSeq[JsonNode](len(node.sons))
     for i, son in node.sons:
       accm[i] = renderRstToJsonNode(son)
diff --git a/lib/packages/docutils/rstgen.nim b/lib/packages/docutils/rstgen.nim
index db9a83755..5b0b6c6ee 100644
--- a/lib/packages/docutils/rstgen.nim
+++ b/lib/packages/docutils/rstgen.nim
@@ -397,9 +397,9 @@ proc hash(x: IndexEntry): Hash =
 proc `<-`(a: var IndexEntry, b: IndexEntry) =
   shallowCopy a.keyword, b.keyword
   shallowCopy a.link, b.link
-  if b.linkTitle.isNil: a.linkTitle = nil
+  if b.linkTitle.isNil: a.linkTitle = ""
   else: shallowCopy a.linkTitle, b.linkTitle
-  if b.linkDesc.isNil: a.linkDesc = nil
+  if b.linkDesc.isNil: a.linkDesc = ""
   else: shallowCopy a.linkDesc, b.linkDesc
 
 proc sortIndex(a: var openArray[IndexEntry]) =
@@ -607,8 +607,8 @@ proc readIndexDir(dir: string):
           fileEntries[F].linkTitle = extraCols[1].unquoteIndexColumn
           fileEntries[F].linkDesc = extraCols[2].unquoteIndexColumn
         else:
-          fileEntries[F].linkTitle = nil
-          fileEntries[F].linkDesc = nil
+          fileEntries[F].linkTitle = ""
+          fileEntries[F].linkDesc = ""
         inc F
       # Depending on type add this to the list of symbols or table of APIs.
       if title.keyword.isNil:
@@ -656,7 +656,6 @@ proc mergeIndexes*(dir: string): string =
   ## Returns the merged and sorted indices into a single HTML block which can
   ## be further embedded into nimdoc templates.
   var (modules, symbols, docs) = readIndexDir(dir)
-  assert(not symbols.isNil)
 
   result = ""
   # Generate a quick jump list of documents.
diff --git a/lib/pure/asyncfutures.nim b/lib/pure/asyncfutures.nim
index 863a6843b..5bf9183ed 100644
--- a/lib/pure/asyncfutures.nim
+++ b/lib/pure/asyncfutures.nim
@@ -219,10 +219,10 @@ proc getHint(entry: StackTraceEntry): string =
   ## We try to provide some hints about stack trace entries that the user
   ## may not be familiar with, in particular calls inside the stdlib.
   result = ""
-  if entry.procname == "processPendingCallbacks":
+  if entry.procname == cstring"processPendingCallbacks":
     if cmpIgnoreStyle(entry.filename, "asyncdispatch.nim") == 0:
       return "Executes pending callbacks"
-  elif entry.procname == "poll":
+  elif entry.procname == cstring"poll":
     if cmpIgnoreStyle(entry.filename, "asyncdispatch.nim") == 0:
       return "Processes asynchronous completion events"
 
diff --git a/lib/pure/asyncnet.nim b/lib/pure/asyncnet.nim
index da7c3473c..71a1600dc 100644
--- a/lib/pure/asyncnet.nim
+++ b/lib/pure/asyncnet.nim
@@ -655,7 +655,7 @@ when defineSsl:
 
   proc wrapConnectedSocket*(ctx: SslContext, socket: AsyncSocket,
                             handshake: SslHandshakeType,
-                            hostname: string = nil) =
+                            hostname: string = "") =
     ## Wraps a connected socket in an SSL context. This function effectively
     ## turns ``socket`` into an SSL socket.
     ## ``hostname`` should be specified so that the client knows which hostname
@@ -670,7 +670,7 @@ when defineSsl:
 
     case handshake
     of handshakeAsClient:
-      if not hostname.isNil and not isIpAddress(hostname):
+      if hostname.len > 0 and not isIpAddress(hostname):
         # Set the SNI address for this connection. This call can fail if
         # we're not using TLSv1+.
         discard SSL_set_tlsext_host_name(socket.sslHandle, hostname)
diff --git a/lib/pure/collections/intsets.nim b/lib/pure/collections/intsets.nim
index bfecfe447..545958977 100644
--- a/lib/pure/collections/intsets.nim
+++ b/lib/pure/collections/intsets.nim
@@ -184,7 +184,7 @@ proc missingOrExcl*(s: var IntSet, key: int) : bool =
   ## `key` is removed from `s` and false is returned.
   var count = s.elems
   exclImpl(s, key)
-  result = count == s.elems 
+  result = count == s.elems
 
 proc containsOrIncl*(s: var IntSet, key: int): bool =
   ## returns true if `s` contains `key`, otherwise `key` is included in `s`
@@ -212,7 +212,10 @@ proc initIntSet*: IntSet =
 
   #newSeq(result.data, InitIntSetSize)
   #result.max = InitIntSetSize-1
-  result.data = nil
+  when defined(nimNoNilSeqs):
+    result.data = @[]
+  else:
+    result.data = nil
   result.max = 0
   result.counter = 0
   result.head = nil
@@ -222,7 +225,10 @@ proc clear*(result: var IntSet) =
   #setLen(result.data, InitIntSetSize)
   #for i in 0..InitIntSetSize-1: result.data[i] = nil
   #result.max = InitIntSetSize-1
-  result.data = nil
+  when defined(nimNoNilSeqs):
+    result.data = @[]
+  else:
+    result.data = nil
   result.max = 0
   result.counter = 0
   result.head = nil
@@ -234,7 +240,10 @@ proc assign*(dest: var IntSet, src: IntSet) =
   ## copies `src` to `dest`. `dest` does not need to be initialized by
   ## `initIntSet`.
   if src.elems <= src.a.len:
-    dest.data = nil
+    when defined(nimNoNilSeqs):
+      dest.data = @[]
+    else:
+      dest.data = nil
     dest.max = 0
     dest.counter = src.counter
     dest.head = nil
@@ -247,11 +256,9 @@ proc assign*(dest: var IntSet, src: IntSet) =
 
     var it = src.head
     while it != nil:
-
       var h = it.key and dest.max
       while dest.data[h] != nil: h = nextTry(h, dest.max)
       assert(dest.data[h] == nil)
-
       var n: PTrunk
       new(n)
       n.next = dest.head
@@ -259,7 +266,6 @@ proc assign*(dest: var IntSet, src: IntSet) =
       n.bits = it.bits
       dest.head = n
       dest.data[h] = n
-
       it = it.next
 
 proc union*(s1, s2: IntSet): IntSet =
@@ -315,7 +321,7 @@ proc len*(s: IntSet): int {.inline.} =
     for _ in s:
       inc(result)
 
-proc card*(s: IntSet): int {.inline.} = 
+proc card*(s: IntSet): int {.inline.} =
   ## alias for `len() <#len>` _.
   result = s.len()
 
@@ -361,7 +367,7 @@ when isMainModule:
   x.incl(1056)
 
   x.incl(1044)
-  x.excl(1044) 
+  x.excl(1044)
 
   assert x.containsOrIncl(888) == false
   assert 888 in x
diff --git a/lib/pure/net.nim b/lib/pure/net.nim
index 771e7de10..0e56100d9 100644
--- a/lib/pure/net.nim
+++ b/lib/pure/net.nim
@@ -231,7 +231,7 @@ proc newSocket*(domain: Domain = AF_INET, sockType: SockType = SOCK_STREAM,
     raiseOSError(osLastError())
   result = newSocket(fd, domain, sockType, protocol, buffered)
 
-proc parseIPv4Address(address_str: string): IpAddress =
+proc parseIPv4Address(addressStr: string): IpAddress =
   ## Parses IPv4 adresses
   ## Raises EInvalidValue on errors
   var
@@ -241,15 +241,15 @@ proc parseIPv4Address(address_str: string): IpAddress =
 
   result.family = IpAddressFamily.IPv4
 
-  for i in 0 .. high(address_str):
-    if address_str[i] in strutils.Digits: # Character is a number
+  for i in 0 .. high(addressStr):
+    if addressStr[i] in strutils.Digits: # Character is a number
       currentByte = currentByte * 10 +
-        cast[uint16](ord(address_str[i]) - ord('0'))
+        cast[uint16](ord(addressStr[i]) - ord('0'))
       if currentByte > 255'u16:
         raise newException(ValueError,
           "Invalid IP Address. Value is out of range")
       seperatorValid = true
-    elif address_str[i] == '.': # IPv4 address separator
+    elif addressStr[i] == '.': # IPv4 address separator
       if not seperatorValid or byteCount >= 3:
         raise newException(ValueError,
           "Invalid IP Address. The address consists of too many groups")
@@ -265,11 +265,11 @@ proc parseIPv4Address(address_str: string): IpAddress =
     raise newException(ValueError, "Invalid IP Address")
   result.address_v4[byteCount] = cast[uint8](currentByte)
 
-proc parseIPv6Address(address_str: string): IpAddress =
+proc parseIPv6Address(addressStr: string): IpAddress =
   ## Parses IPv6 adresses
   ## Raises EInvalidValue on errors
   result.family = IpAddressFamily.IPv6
-  if address_str.len < 2:
+  if addressStr.len < 2:
     raise newException(ValueError, "Invalid IP Address")
 
   var
@@ -282,7 +282,7 @@ proc parseIPv6Address(address_str: string): IpAddress =
     v4StartPos = -1
     byteCount = 0
 
-  for i,c in address_str:
+  for i,c in addressStr:
     if c == ':':
       if not seperatorValid:
         raise newException(ValueError,
@@ -293,7 +293,7 @@ proc parseIPv6Address(address_str: string): IpAddress =
             "Invalid IP Address. Address contains more than one \"::\" seperator")
         dualColonGroup = groupCount
         seperatorValid = false
-      elif i != 0 and i != high(address_str):
+      elif i != 0 and i != high(addressStr):
         if groupCount >= 8:
           raise newException(ValueError,
             "Invalid IP Address. The address consists of too many groups")
@@ -303,11 +303,11 @@ proc parseIPv6Address(address_str: string): IpAddress =
         groupCount.inc()
         if dualColonGroup != -1: seperatorValid = false
       elif i == 0: # only valid if address starts with ::
-        if address_str[1] != ':':
+        if addressStr[1] != ':':
           raise newException(ValueError,
             "Invalid IP Address. Address may not start with \":\"")
-      else: # i == high(address_str) - only valid if address ends with ::
-        if address_str[high(address_str)-1] != ':':
+      else: # i == high(addressStr) - only valid if address ends with ::
+        if addressStr[high(addressStr)-1] != ':':
           raise newException(ValueError,
             "Invalid IP Address. Address may not end with \":\"")
       lastWasColon = true
@@ -345,7 +345,7 @@ proc parseIPv6Address(address_str: string): IpAddress =
       result.address_v6[groupCount*2+1] = cast[uint8](currentShort and 0xFF)
       groupCount.inc()
   else: # Must parse IPv4 address
-    for i,c in address_str[v4StartPos..high(address_str)]:
+    for i,c in addressStr[v4StartPos..high(addressStr)]:
       if c in strutils.Digits: # Character is a number
         currentShort = currentShort * 10 + cast[uint32](ord(c) - ord('0'))
         if currentShort > 255'u32:
@@ -386,21 +386,21 @@ proc parseIPv6Address(address_str: string): IpAddress =
     raise newException(ValueError,
       "Invalid IP Address. The address consists of too many groups")
 
-proc parseIpAddress*(address_str: string): IpAddress =
+proc parseIpAddress*(addressStr: string): IpAddress =
   ## Parses an IP address
   ## Raises EInvalidValue on error
-  if address_str == nil:
-    raise newException(ValueError, "IP Address string is nil")
-  if address_str.contains(':'):
-    return parseIPv6Address(address_str)
+  if addressStr.len == 0:
+    raise newException(ValueError, "IP Address string is empty")
+  if addressStr.contains(':'):
+    return parseIPv6Address(addressStr)
   else:
-    return parseIPv4Address(address_str)
+    return parseIPv4Address(addressStr)
 
-proc isIpAddress*(address_str: string): bool {.tags: [].} =
+proc isIpAddress*(addressStr: string): bool {.tags: [].} =
   ## Checks if a string is an IP address
   ## Returns true if it is, false otherwise
   try:
-    discard parseIpAddress(address_str)
+    discard parseIpAddress(addressStr)
   except ValueError:
     return false
   return true
@@ -587,7 +587,7 @@ when defineSsl:
   proc pskClientCallback(ssl: SslPtr; hint: cstring; identity: cstring; max_identity_len: cuint; psk: ptr cuchar;
     max_psk_len: cuint): cuint {.cdecl.} =
     let ctx = SSLContext(context: ssl.SSL_get_SSL_CTX)
-    let hintString = if hint == nil: nil else: $hint
+    let hintString = if hint == nil: "" else: $hint
     let (identityString, pskString) = (ctx.clientGetPskFunc)(hintString)
     if psk.len.cuint > max_psk_len:
       return 0
@@ -657,7 +657,7 @@ when defineSsl:
 
   proc wrapConnectedSocket*(ctx: SSLContext, socket: Socket,
                             handshake: SslHandshakeType,
-                            hostname: string = nil) =
+                            hostname: string = "") =
     ## Wraps a connected socket in an SSL context. This function effectively
     ## turns ``socket`` into an SSL socket.
     ## ``hostname`` should be specified so that the client knows which hostname
@@ -671,7 +671,7 @@ when defineSsl:
     wrapSocket(ctx, socket)
     case handshake
     of handshakeAsClient:
-      if not hostname.isNil and not isIpAddress(hostname):
+      if hostname.len > 0 and not isIpAddress(hostname):
         # Discard result in case OpenSSL version doesn't support SNI, or we're
         # not using TLSv1+
         discard SSL_set_tlsext_host_name(socket.sslHandle, hostname)
diff --git a/lib/pure/parseopt2.nim b/lib/pure/parseopt2.nim
index b54a56c0c..51a70b6d1 100644
--- a/lib/pure/parseopt2.nim
+++ b/lib/pure/parseopt2.nim
@@ -44,10 +44,10 @@ type
 proc initOptParser*(cmdline: seq[string]): OptParser {.rtl.} =
   ## Initalizes option parses with cmdline. cmdline should not contain
   ## argument 0 - program name.
-  ## If cmdline == nil default to current command line arguments.
+  ## If cmdline.len == 0 default to current command line arguments.
   result.remainingShortOptions = ""
   when not defined(createNimRtl):
-    if cmdline == nil:
+    if cmdline.len == 0:
       result.cmd = commandLineParams()
       return
   else:
@@ -60,7 +60,7 @@ proc initOptParser*(cmdline: string): OptParser {.rtl, deprecated.} =
   ## and calls initOptParser(openarray[string])
   ## Do not use.
   if cmdline == "": # backward compatibility
-    return initOptParser(seq[string](nil))
+    return initOptParser(@[])
   else:
     return initOptParser(cmdline.split)
 
diff --git a/lib/pure/parsexml.nim b/lib/pure/parsexml.nim
index e0000aad3..fe933fb79 100644
--- a/lib/pure/parsexml.nim
+++ b/lib/pure/parsexml.nim
@@ -95,6 +95,7 @@ type
     kind: XmlEventKind
     err: XmlErrorKind
     state: ParserState
+    cIsEmpty: bool
     filename: string
     options: set[XmlParseOption]
 
@@ -125,7 +126,8 @@ proc open*(my: var XmlParser, input: Stream, filename: string,
   my.kind = xmlError
   my.a = ""
   my.b = ""
-  my.c = nil
+  my.c = ""
+  my.cIsEmpty = true
   my.options = options
 
 proc close*(my: var XmlParser) {.inline.} =
@@ -482,6 +484,7 @@ proc parseTag(my: var XmlParser) =
     my.kind = xmlElementOpen
     my.state = stateAttr
     my.c = my.a # save for later
+    my.cIsEmpty = false
   else:
     my.kind = xmlElementStart
     let slash = my.buf[my.bufpos] == '/'
@@ -490,7 +493,8 @@ proc parseTag(my: var XmlParser) =
     if slash and my.buf[my.bufpos] == '>':
       inc(my.bufpos)
       my.state = stateEmptyElementTag
-      my.c = nil
+      my.c = ""
+      my.cIsEmpty = true
     elif my.buf[my.bufpos] == '>':
       inc(my.bufpos)
     else:
@@ -678,7 +682,7 @@ proc next*(my: var XmlParser) =
   of stateEmptyElementTag:
     my.state = stateNormal
     my.kind = xmlElementEnd
-    if not my.c.isNil:
+    if not my.cIsEmpty:
       my.a = my.c
   of stateError:
     my.kind = xmlError
diff --git a/lib/pure/pegs.nim b/lib/pure/pegs.nim
index d16527a56..b22016a3a 100644
--- a/lib/pure/pegs.nim
+++ b/lib/pure/pegs.nim
@@ -765,7 +765,7 @@ template fillMatches(s, caps, c) =
     if startIdx != -1:
       caps[k] = substr(s, startIdx, endIdx)
     else:
-      caps[k] = nil
+      caps[k] = ""
 
 proc matchLen*(s: string, pattern: Peg, matches: var openArray[string],
                start = 0): int {.nosideEffect, rtl, extern: "npegs$1Capture".} =
diff --git a/lib/pure/streams.nim b/lib/pure/streams.nim
index 1ab73faea..09626136f 100644
--- a/lib/pure/streams.nim
+++ b/lib/pure/streams.nim
@@ -377,7 +377,10 @@ when not defined(js):
 
   proc ssClose(s: Stream) =
     var s = StringStream(s)
-    s.data = nil
+    when defined(nimNoNilSeqs):
+      s.data = ""
+    else:
+      s.data = nil
 
   proc newStringStream*(s: string = ""): StringStream =
     ## creates a new stream from the string `s`.
diff --git a/lib/pure/unittest.nim b/lib/pure/unittest.nim
index aa07a4fa6..f4b89b2d0 100644
--- a/lib/pure/unittest.nim
+++ b/lib/pure/unittest.nim
@@ -176,10 +176,7 @@ method suiteEnded*(formatter: OutputFormatter) {.base, gcsafe.} =
   discard
 
 proc addOutputFormatter*(formatter: OutputFormatter) =
-  if formatters == nil:
-    formatters = @[formatter]
-  else:
-    formatters.add(formatter)
+  formatters.add(formatter)
 
 proc newConsoleOutputFormatter*(outputLevel: OutputLevel = PRINT_ALL,
                                 colorOutput = true): ConsoleOutputFormatter =
@@ -225,7 +222,7 @@ method testStarted*(formatter: ConsoleOutputFormatter, testName: string) =
   formatter.isInTest = true
 
 method failureOccurred*(formatter: ConsoleOutputFormatter, checkpoints: seq[string], stackTrace: string) =
-  if stackTrace != nil:
+  if stackTrace.len > 0:
     echo stackTrace
   let prefix = if formatter.isInSuite: "    " else: ""
   for msg in items(checkpoints):
@@ -236,7 +233,7 @@ method testEnded*(formatter: ConsoleOutputFormatter, testResult: TestResult) =
 
   if formatter.outputLevel != PRINT_NONE and
      (formatter.outputLevel == PRINT_ALL or testResult.status == FAILED):
-    let prefix = if testResult.suiteName != nil: "  " else: ""
+    let prefix = if testResult.suiteName.len > 0: "  " else: ""
     template rawPrint() = echo(prefix, "[", $testResult.status, "] ", testResult.testName)
     when not defined(ECMAScript):
       if formatter.colorOutput and not defined(ECMAScript):
@@ -301,7 +298,7 @@ method failureOccurred*(formatter: JUnitOutputFormatter, checkpoints: seq[string
   ## ``stackTrace`` is provided only if the failure occurred due to an exception.
   ## ``checkpoints`` is never ``nil``.
   formatter.testErrors.add(checkpoints)
-  if stackTrace != nil:
+  if stackTrace.len > 0:
     formatter.testStackTrace = stackTrace
 
 method testEnded*(formatter: JUnitOutputFormatter, testResult: TestResult) =
@@ -392,7 +389,7 @@ proc shouldRun(currentSuiteName, testName: string): bool =
   return false
 
 proc ensureInitialized() =
-  if formatters == nil:
+  if formatters.len == 0:
     formatters = @[OutputFormatter(defaultConsoleFormatter())]
 
   if not disabledParamFiltering and not testsFilters.isValid:
diff --git a/lib/pure/xmldom.nim b/lib/pure/xmldom.nim
index 8cd47aa39..1a9e4ae26 100644
--- a/lib/pure/xmldom.nim
+++ b/lib/pure/xmldom.nim
@@ -217,9 +217,9 @@ proc createAttribute*(doc: PDocument, name: string): PAttr =
   new(attrNode)
   attrNode.fName = name
   attrNode.fNodeName = name
-  attrNode.fLocalName = nil
-  attrNode.prefix = nil
-  attrNode.fNamespaceURI = nil
+  attrNode.fLocalName = ""
+  attrNode.prefix = ""
+  attrNode.fNamespaceURI = ""
   attrNode.value = ""
   attrNode.fSpecified = false
   return attrNode
@@ -254,7 +254,7 @@ proc createAttributeNS*(doc: PDocument, namespaceURI: string, qualifiedName: str
     attrNode.prefix = qualifiedName.split(':')[0]
     attrNode.fLocalName = qualifiedName.split(':')[1]
   else:
-    attrNode.prefix = nil
+    attrNode.prefix = ""
     attrNode.fLocalName = qualifiedName
   attrNode.value = ""
 
@@ -298,9 +298,9 @@ proc createElement*(doc: PDocument, tagName: string): PElement =
   new(elNode)
   elNode.fTagName = tagName
   elNode.fNodeName = tagName
-  elNode.fLocalName = nil
-  elNode.prefix = nil
-  elNode.fNamespaceURI = nil
+  elNode.fLocalName = ""
+  elNode.prefix = ""
+  elNode.fNamespaceURI = ""
   elNode.childNodes = @[]
   elNode.attributes = @[]
 
@@ -332,7 +332,7 @@ proc createElementNS*(doc: PDocument, namespaceURI: string, qualifiedName: strin
     elNode.prefix = qualifiedName.split(':')[0]
     elNode.fLocalName = qualifiedName.split(':')[1]
   else:
-    elNode.prefix = nil
+    elNode.prefix = ""
     elNode.fLocalName = qualifiedName
   elNode.fNamespaceURI = namespaceURI
   elNode.childNodes = @[]
@@ -893,22 +893,22 @@ proc tagName*(el: PElement): string =
 proc getAttribute*(el: PNode, name: string): string =
   ## Retrieves an attribute value by ``name``
   if isNil(el.attributes):
-    return nil
+    return ""
   var attribute = el.attributes.getNamedItem(name)
   if not isNil(attribute):
     return attribute.value
   else:
-    return nil
+    return ""
 
 proc getAttributeNS*(el: PNode, namespaceURI: string, localName: string): string =
   ## Retrieves an attribute value by ``localName`` and ``namespaceURI``
   if isNil(el.attributes):
-    return nil
+    return ""
   var attribute = el.attributes.getNamedItemNS(namespaceURI, localName)
   if not isNil(attribute):
     return attribute.value
   else:
-    return nil
+    return ""
 
 proc getAttributeNode*(el: PElement, name: string): PAttr =
   ## Retrieves an attribute node by ``name``
diff --git a/lib/pure/xmldomparser.nim b/lib/pure/xmldomparser.nim
index 7c7f7b99c..8d995102e 100644
--- a/lib/pure/xmldomparser.nim
+++ b/lib/pure/xmldomparser.nim
@@ -119,7 +119,7 @@ proc loadXMLStream*(stream: Stream): PDocument =
   ## a ``PDocument``
 
   var x: XmlParser
-  open(x, stream, nil, {reportComments})
+  open(x, stream, "", {reportComments})
 
   var xmlDoc: PDocument
   var dom: PDOMImplementation = getDOM()
@@ -161,7 +161,7 @@ when not defined(testing) and isMainModule:
   #echo(xml.getElementsByTagName("bla:test")[0].namespaceURI)
   #echo(xml.getElementsByTagName("test")[0].namespaceURI)
   for i in items(xml.getElementsByTagName("*")):
-    if i.namespaceURI != nil:
+    if i.namespaceURI.len > 0:
       echo(i.nodeName, "=", i.namespaceURI)
 
 
diff --git a/lib/system.nim b/lib/system.nim
index b92dd58d6..4b69a8067 100644
--- a/lib/system.nim
+++ b/lib/system.nim
@@ -3963,19 +3963,28 @@ when hasAlloc:
   proc safeAdd*[T](x: var seq[T], y: T) {.noSideEffect, deprecated.} =
     ## Adds ``y`` to ``x`` unless ``x`` is not yet initialized; in that case,
     ## ``x`` becomes ``@[y]``
-    if x == nil: x = @[y]
-    else: x.add(y)
+    when defined(nimNoNilSeqs):
+      x.add(y)
+    else:
+      if x == nil: x = @[y]
+      else: x.add(y)
 
   proc safeAdd*(x: var string, y: char) {.noSideEffect, deprecated.} =
     ## Adds ``y`` to ``x``. If ``x`` is ``nil`` it is initialized to ``""``
-    if x == nil: x = ""
-    x.add(y)
+    when defined(nimNoNilSeqs):
+      x.add(y)
+    else:
+      if x == nil: x = ""
+      x.add(y)
 
   proc safeAdd*(x: var string, y: string) {.noSideEffect, deprecated.} =
     ## Adds ``y`` to ``x`` unless ``x`` is not yet initalized; in that
     ## case, ``x`` becomes ``y``
-    if x == nil: x = y
-    else: x.add(y)
+    when defined(nimNoNilSeqs):
+      x.add(y)
+    else:
+      if x == nil: x = y
+      else: x.add(y)
 
 proc locals*(): RootObj {.magic: "Plugin", noSideEffect.} =
   ## generates a tuple constructor expression listing all the local variables