fixes the recently discovered GC memory leaks

This revision is intended as comparison point between the old and the new GC
The used GC can be switched in mmdisp and various statistics will be gathered during
execution (these will be removed/disabled in later revisions)

lib/system/cellsets.nim

@@ -10,8 +10,10 @@
 # Efficient set of pointers for the GC (and repr)
 
 type
+  TRefCount = int
+
   TCell {.pure.} = object
-    refcount: int  # the refcount and some flags
+    refcount: TRefCount  # the refcount and some flags
     typ: PNimType
     when trackAllocationSource:
       filename: cstring

lib/system/hti.nim

@@ -13,11 +13,19 @@ when defined(NimString):
 else:
   {.pragma: codegenType.}
 
-type # This should be he same as ast.TTypeKind
-     # many enum fields are not used at runtime
+type 
+  # This should be he same as ast.TTypeKind
+  # many enum fields are not used at runtime
   TNimKind = enum
-    tyNone, tyBool, tyChar,
-    tyEmpty, tyArrayConstr, tyNil, tyExpr, tyStmt, tyTypeDesc,
+    tyNone,
+    tyBool,
+    tyChar,
+    tyEmpty,
+    tyArrayConstr,
+    tyNil,
+    tyExpr,
+    tyStmt,
+    tyTypeDesc,
     tyGenericInvokation, # ``T[a, b]`` for types to invoke
     tyGenericBody,       # ``T[a, b, body]`` last parameter is the body
     tyGenericInst,       # ``T[a, b, realInstance]`` instantiated generic type
@@ -30,15 +38,30 @@ type # This should be he same as ast.TTypeKind
     tyTuple,             # WARNING: The compiler uses tyTuple for pure objects!
     tySet,
     tyRange,
-    tyPtr, tyRef,
+    tyPtr,
+    tyRef,
     tyVar,
     tySequence,
     tyProc,
-    tyPointer, tyOpenArray,
-    tyString, tyCString, tyForward,
-    tyInt, tyInt8, tyInt16, tyInt32, tyInt64,
-    tyFloat, tyFloat32, tyFloat64, tyFloat128,
-    tyUInt, tyUInt8, tyUInt16, tyUInt32, tyUInt64,
+    tyPointer,
+    tyOpenArray,
+    tyString,
+    tyCString,
+    tyForward,
+    tyInt,
+    tyInt8,
+    tyInt16,
+    tyInt32,
+    tyInt64,
+    tyFloat,
+    tyFloat32,
+    tyFloat64,
+    tyFloat128,
+    tyUInt,
+    tyUInt8,
+    tyUInt16,
+    tyUInt32,
+    tyUInt64,
     tyBigNum,
 
   TNimNodeKind = enum nkNone, nkSlot, nkList, nkCase

lib/system/mmdisp.nim

@@ -14,9 +14,9 @@
 {.push checks:off.}
 
 const
-  debugGC = false # we wish to debug the GC...
+  debugGC = true # we wish to debug the GC...
   logGC = false
-  traceGC = false # extensive debugging
+  traceGC = true # extensive debugging
   alwaysCycleGC = false
   alwaysGC = false # collect after every memory allocation (for debugging)
   leakDetector = false
@@ -307,7 +307,10 @@ else:
   include "system/cellsets"
   when not leakDetector:
     sysAssert(sizeof(TCell) == sizeof(TFreeCell), "sizeof TFreeCell")
-  include "system/gc"
+  when true:
+    include "system/gc"
+  else:
+    include "system/oldgc"
   
 {.pop.}
 

lib/system/sysstr.nim

@@ -204,9 +204,16 @@ proc setLengthSeq(seq: PGenericSeq, elemSize, newLen: int): PGenericSeq {.
     # we need to decref here, otherwise the GC leaks!
     when not defined(boehmGC) and not defined(nogc):
       for i in newLen..result.len-1:
+        let len0 = gch.tempStack.len
         forAllChildrenAux(cast[pointer](cast[TAddress](result) +%
                           GenericSeqSize +% (i*%elemSize)),
-                          extGetCellType(result).base, waZctDecRef)
+                          extGetCellType(result).base, waPush)
+        let len1 = gch.tempStack.len
+        for i in len0 .. <len1:
+          doDecRef(gch.tempStack.d[i], LocalHeap, MaybeCyclic)
+        gch.tempStack.len = len0
+                          
+        # XXX add a proper addCycleRoot barrier here!
     # and set the memory to nil:
     zeroMem(cast[pointer](cast[TAddress](result) +% GenericSeqSize +%
            (newLen*%elemSize)), (result.len-%newLen) *% elemSize)

lib/system/timers.nim

@@ -44,10 +44,11 @@ elif defined(macosx):
 
   proc getTicks(): TTicks {.inline.} =
     result = TTicks(mach_absolute_time())
-
+  
+  var timeBaseInfo: TMachTimebaseInfoData
+  mach_timebase_info(timeBaseInfo)
+    
   proc `-`(a, b: TTicks): TNanos =
-    var timeBaseInfo: TMachTimebaseInfoData
-    mach_timebase_info(timeBaseInfo)
     result = (a.int64 - b.int64)  * timeBaseInfo.numer div timeBaseInfo.denom
 
 elif defined(posixRealtime):