refactor memory management structures for consistency across modules

lib/system/alloc.nim

@@ -104,6 +104,8 @@ type
       zeroField: int       # 0 means cell is not used (overlaid with typ field)
                           # 1 means cell is manually managed pointer
                           # otherwise a PNimType is stored in there
+      when sizeof(int) == 4:  # 32-bit only
+        headerAlignPad: array[8, byte]  # so addr(data) ≡ 8 (mod 16)
     else:
       alignment: int
 

lib/system/cellsets.nim

@@ -48,7 +48,23 @@ when defined(gcOrc) or defined(gcArc) or defined(gcAtomicArc) or defined(gcYrc):
 
   when not declaredInScope(PageShift):
     include bitmasks
+else:
+  type
+    RefCount = int
 
+    Cell {.pure.} = object
+      refcount: RefCount  # the refcount and some flags
+      typ: PNimType
+
+      when trackAllocationSource:
+        filename: cstring
+        line: int
+      elif useCellIds:
+        id: int
+      elif defined(cpu32):
+        headerAlignPad: array[8, byte]  # so addr(data) ≡ 8 (mod 16)
+
+    PCell = ptr Cell
 
 type
   PPageDesc = ptr PageDesc

lib/system/mmdisp.nim

@@ -38,24 +38,6 @@ type
   PByte = ptr ByteArray
   PString = ptr string
 
-when not defined(nimV2):
-  type
-    RefCount = int
-
-    Cell {.pure.} = object
-      refcount: RefCount  # the refcount and some flags
-      typ: PNimType
-      when sizeof(int) == 4:  # 32-bit only
-        headerAlignPad: array[8, byte]  # so addr(data) ≡ 8 (mod 16)
-
-      when trackAllocationSource:
-        filename: cstring
-        line: int
-      when useCellIds:
-        id: int
-
-    PCell = ptr Cell
-
 when declared(IntsPerTrunk):
   discard
 else:
@@ -96,7 +78,7 @@ else:
     when not usesDestructors:
       include "system/cellsets"
     when not leakDetector and not useCellIds and not defined(nimV2):
-      sysAssert(sizeof(FreeCell) <= sizeof(Cell), "sizeof FreeCell")
+      sysAssert(sizeof(FreeCell) == sizeof(Cell), "sizeof FreeCell")
   when defined(gcRegions):
     # XXX due to bootstrapping reasons, we cannot use  compileOption("gc", "stack") here
     include "system/gc_regions"