make memory regions robust; disable free lists for now

lib/system/gc_regions.nim

@@ -70,6 +70,7 @@ type
     bump: pointer
     head, tail: Chunk
     nextChunkSize, totalSize: int
+    when false:
       freeLists: array[MaxSmallObject div MemAlign, FreeEntry]
       holes: SizedFreeEntry
     when hasThreadSupport:
@@ -145,6 +146,7 @@ proc allocSlowPath(r: var MemRegion; size: int) =
   r.remaining = s - sizeof(BaseChunk)
 
 proc allocFast(r: var MemRegion; size: int): pointer =
+  when false:
     if size <= MaxSmallObject:
       var it = r.freeLists[size div MemAlign]
       if it != nil:
@@ -184,7 +186,8 @@ proc dealloc(r: var MemRegion; p: pointer; size: int) =
   # it is benefitial to not use the free lists here:
   if r.bump -! size == p:
     dec r.bump, size
-  elif size <= MaxSmallObject:
+  when false:
+    if size <= MaxSmallObject:
       let it = cast[FreeEntry](p)
       it.next = r.freeLists[size div MemAlign]
       r.freeLists[size div MemAlign] = it
@@ -220,6 +223,7 @@ proc setObstackPtr*(r: var MemRegion; sp: StackPtr) =
   if sp.current.next != nil:
     deallocAll(r, sp.current.next)
     sp.current.next = nil
+    when false:
       # better leak this memory than be sorry:
       for i in 0..high(r.freeLists): r.freeLists[i] = nil
       r.holes = nil