the compiler does not rely on the zero terminator anymore

compiler/lexer.nim

@@ -165,13 +165,12 @@ proc isKeyword*(kind: TTokType): bool =
 template ones(n): untyped = ((1 shl n)-1) # for utf-8 conversion
 
 proc isNimIdentifier*(s: string): bool =
-  if s[0] in SymStartChars:
+  let sLen = s.len
+  if sLen > 0 and s[0] in SymStartChars:
     var i = 1
-    var sLen = s.len
     while i < sLen:
-      if s[i] == '_':
-        inc(i)
-      if s[i] notin SymChars: return
+      if s[i] == '_': inc(i)
+      if i < sLen and s[i] notin SymChars: return
       inc(i)
     result = true
 
@@ -311,12 +310,12 @@ template tokenEndPrevious(tok, pos) =
 # We need to parse the largest uint literal without overflow checks
 proc unsafeParseUInt(s: string, b: var BiggestInt, start = 0): int =
   var i = start
-  if s[i] in {'0'..'9'}:
+  if i < s.len and s[i] in {'0'..'9'}:
     b = 0
-    while s[i] in {'0'..'9'}:
+    while i < s.len and s[i] in {'0'..'9'}:
       b = b * 10 + (ord(s[i]) - ord('0'))
       inc(i)
-      while s[i] == '_': inc(i) # underscores are allowed and ignored
+      while i < s.len and s[i] == '_': inc(i) # underscores are allowed and ignored
     result = i - start
 {.pop.} # overflowChecks
 

compiler/ropes.nim

@@ -251,7 +251,7 @@ proc `%`*(frmt: FormatStr, args: openArray[Rope]): Rope =
         while true:
           j = j * 10 + ord(frmt[i]) - ord('0')
           inc(i)
-          if frmt[i] notin {'0'..'9'}: break
+          if i >= frmt.len or frmt[i] notin {'0'..'9'}: break
         num = j
         if j > high(args) + 1:
           errorHandler(rInvalidFormatStr, $(j))

compiler/syntaxes.nim

@@ -51,15 +51,15 @@ proc parseTopLevelStmt*(p: var TParsers): PNode =
     result = ast.emptyNode
 
 proc utf8Bom(s: string): int =
-  if s[0] == '\xEF' and s[1] == '\xBB' and s[2] == '\xBF':
+  if s.len >= 3 and s[0] == '\xEF' and s[1] == '\xBB' and s[2] == '\xBF':
     result = 3
   else:
     result = 0
 
 proc containsShebang(s: string, i: int): bool =
-  if s[i] == '#' and s[i+1] == '!':
+  if i+1 < s.len and s[i] == '#' and s[i+1] == '!':
     var j = i + 2
-    while s[j] in Whitespace: inc(j)
+    while j < s.len and s[j] in Whitespace: inc(j)
     result = s[j] == '/'
 
 proc parsePipe(filename: string, inputStream: PLLStream; cache: IdentCache): PNode =
@@ -74,9 +74,9 @@ proc parsePipe(filename: string, inputStream: PLLStream; cache: IdentCache): PNo
       discard llStreamReadLine(s, line)
       i = 0
       inc linenumber
-    if line[i] == '#' and line[i+1] == '?':
+    if i+1 < line.len and line[i] == '#' and line[i+1] == '?':
       inc(i, 2)
-      while line[i] in Whitespace: inc(i)
+      while i < line.len and line[i] in Whitespace: inc(i)
       var q: TParser
       parser.openParser(q, filename, llStreamOpen(substr(line, i)), cache)
       result = parser.parseAll(q)