[project @ 2001-05-18 09:18:05 by simonmar]

[ghc-hetmet.git] / ghc / includes / Stable.h

diff --git a/ghc/includes/Stable.h b/ghc/includes/Stable.h
index c868504..66486bd 100644 (file)
--- a/ghc/includes/Stable.h
+++ b/ghc/includes/Stable.h
@@ -1,11 +1,21 @@
 /* -----------------------------------------------------------------------------
- * $Id: Stable.h,v 1.5 2000/04/13 15:37:11 panne Exp $
+ * $Id: Stable.h,v 1.7 2000/11/07 17:05:47 simonmar Exp $
  *
- * (c) The GHC Team, 1998-1999
+ * (c) The GHC Team, 1998-2000
  *
- * Stable names and stable pointers
+ * Stable Pointers: A stable pointer is represented as an index into
+ * the stable pointer table in the low BITS_PER_WORD-8 bits with a
+ * weight in the upper 8 bits.
  *
- * ---------------------------------------------------------------------------*/
+ * SUP: StgStablePtr used to be a synonym for StgWord, but stable pointers
+ * are guaranteed to be void* on the C-side, so we have to do some occasional
+ * casting. Size is not a matter, because StgWord is always the same size as
+ * a void*.
+ *
+ * ----------------------------------------------------------------------------*/
+
+#define STABLEPTR_WEIGHT_MASK   ((StgWord)0xff << ((sizeof(StgWord)-1) * BITS_PER_BYTE))
+#define STABLEPTR_WEIGHT_SHIFT  (BITS_IN(StgWord) - 8)
 
 /* -----------------------------------------------------------------------------
    External C Interface
@@ -48,7 +58,8 @@ freeStablePtr(StgStablePtr sp)
         && stable_ptr_table[sn].addr != NULL
         && stable_ptr_table[sn].weight > 0);
   
-  stable_ptr_table[sn].weight += (stgCast(StgWord,sp) & STABLEPTR_WEIGHT_MASK) >> STABLEPTR_WEIGHT_SHIFT;
+  stable_ptr_table[sn].weight += 
+      1 << ((((StgWord)sp & STABLEPTR_WEIGHT_MASK) >> STABLEPTR_WEIGHT_SHIFT) - 1);
 }
 
 extern inline StgStablePtr