better error message for subtle nil errors

compiler/cgen.nim

@@ -346,6 +346,8 @@ proc resetLoc(p: BProc, loc: var TLoc) =
     else:
       linefmt(p, cpsStmts, "$1 = 0;$n", rdLoc(loc))
   else:
+    if optNilCheck in p.options:
+      linefmt(p, cpsStmts, "#chckNil((void*)$1);$n", addrLoc(loc))
     if loc.s != OnStack:
       linefmt(p, cpsStmts, "#genericReset((void*)$1, $2);$n",
               addrLoc(loc), genTypeInfo(p.module, loc.t))

compiler/options.nim

@@ -92,7 +92,7 @@ var
   gOptions*: TOptions = {optObjCheck, optFieldCheck, optRangeCheck, 
                          optBoundsCheck, optOverflowCheck, optAssert, optWarns, 
                          optHints, optStackTrace, optLineTrace,
-                         optPatterns}
+                         optPatterns, optNilCheck}
   gGlobalOptions*: TGlobalOptions = {optThreadAnalysis}
   gExitcode*: int8
   gCmd*: TCommands = cmdNone  # the command

lib/system/excpt.nim

@@ -32,7 +32,7 @@ proc registerSignalHandler()
 proc chckIndx(i, a, b: int): int {.inline, compilerproc.}
 proc chckRange(i, a, b: int): int {.inline, compilerproc.}
 proc chckRangeF(x, a, b: float): float {.inline, compilerproc.}
-proc chckNil(p: pointer) {.inline, compilerproc.}
+proc chckNil(p: pointer) {.noinline, compilerproc.}
 
 var
   framePtr {.rtlThreadVar.}: PFrame
@@ -359,7 +359,9 @@ proc chckRangeF(x, a, b: float): float =
     raise newException(EOutOfRange, "value " & $x & " out of range")
 
 proc chckNil(p: pointer) =
-  if p == nil: c_raise(SIGSEGV)
+  if p == nil:
+    raise newException(EInvalidValue, "attempt to write to a nil address")
+    #c_raise(SIGSEGV)
 
 proc chckObj(obj, subclass: PNimType) {.compilerproc.} =
   # checks if obj is of type subclass:

todo.txt

@@ -9,6 +9,7 @@ version 0.9.4
   - overloading of ``.``? Special case ``.=``?
 - built-in 'getImpl'
 - macros.gensym still missing?
+- optimize 'genericReset'; 'newException' leads to code bloat
 
 
 Bugs