bugfix: --gc:none -d:useMalloc works again

lib/system/excpt.nim

@@ -27,8 +27,6 @@ else:
   proc writeToStdErr(msg: CString) =
     discard MessageBoxA(0, msg, nil, 0)
 
-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.}
@@ -278,7 +276,8 @@ when defined(endb):
   var
     dbgAborting: bool # whether the debugger wants to abort
 
-proc signalHandler(sig: cint) {.exportc: "signalHandler", noconv.} =
+when not defined(noSignalHandler):
+  proc signalHandler(sig: cint) {.exportc: "signalHandler", noconv.} =
     template processSignal(s, action: expr) {.immediate.} =
       if s == SIGINT: action("SIGINT: Interrupted by Ctrl-C.\n")
       elif s == SIGSEGV: 
@@ -309,7 +308,7 @@ proc signalHandler(sig: cint) {.exportc: "signalHandler", noconv.} =
     when defined(endb): dbgAborting = True
     quit(1) # always quit when SIGABRT
 
-proc registerSignalHandler() =
+  proc registerSignalHandler() =
     c_signal(SIGINT, signalHandler)
     c_signal(SIGSEGV, signalHandler)
     c_signal(SIGABRT, signalHandler)
@@ -317,7 +316,6 @@ proc registerSignalHandler() =
     c_signal(SIGILL, signalHandler)
     c_signal(SIGBUS, signalHandler)
 
-when not defined(noSignalHandler):
   registerSignalHandler() # call it in initialization section
 
 proc setControlCHook(hook: proc () {.noconv.}) =

lib/system/repr.nim

@@ -117,6 +117,7 @@ proc reprSet(p: pointer, typ: PNimType): string {.compilerRtl.} =
 type
   TReprClosure {.final.} = object # we cannot use a global variable here
                                   # as this wouldn't be thread-safe
+    when defined(TCellSet):
       marked: TCellSet
     recdepth: int       # do not recurse endlessly
     indent: int         # indentation
@@ -127,12 +128,13 @@ when not defined(useNimRtl):
     # have to do it here ...
     when hasThreadSupport and hasSharedHeap and defined(heapLock):
       AcquireSys(HeapLock)
+    when defined(TCellSet):
       Init(cl.marked)
     cl.recdepth = -1      # default is to display everything!
     cl.indent = 0
 
   proc deinitReprClosure(cl: var TReprClosure) =
-    Deinit(cl.marked)
+    when defined(TCellSet): Deinit(cl.marked)
     when hasThreadSupport and hasSharedHeap and defined(heapLock): 
       ReleaseSys(HeapLock)
 
@@ -195,6 +197,7 @@ when not defined(useNimRtl):
   proc reprRef(result: var string, p: pointer, typ: PNimType,
                cl: var TReprClosure) =
     # we know that p is not nil here:
+    when defined(TCellSet):
       when defined(boehmGC) or defined(nogc):
         var cell = cast[PCell](p)
       else: