MemSet() must not cast its pointer argument to int32* until after it has

checked that the pointer is actually word-aligned.  Casting a non-aligned
pointer to int32* is technically illegal per the C spec, and some recent
versions of gcc actually generate bad code for the memset() when given
such a pointer.  Per report from Andrew Morrow.

diff --git a/src/include/c.h b/src/include/c.h
index 4567e2102d551094052093ae443bf6f44fe08480..7752e1ae02d67354d1b50b9838163d805ee02dcb 100644 (file)
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/c.h,v 1.187 2005/07/02 17:01:52 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/c.h,v 1.188 2005/07/18 15:53:28 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -630,21 +630,22 @@ typedef NameData *Name;
 #define MemSet(start, val, len) \
        do \
        { \
-               int32  *_start = (int32 *) (start); \
+               void   *_vstart = (void *) (start); \
                int             _val = (val); \
                Size    _len = (len); \
 \
-               if ((((long) _start) & INT_ALIGN_MASK) == 0 && \
+               if ((((long) _vstart) & INT_ALIGN_MASK) == 0 && \
                        (_len & INT_ALIGN_MASK) == 0 && \
                        _val == 0 && \
                        _len <= MEMSET_LOOP_LIMIT) \
                { \
+                       int32 *_start = (int32 *) _vstart; \
                        int32 *_stop = (int32 *) ((char *) _start + _len); \
                        while (_start < _stop) \
                                *_start++ = 0; \
                } \
                else \
-                       memset(_start, _val, _len); \
+                       memset(_vstart, _val, _len); \
        } while (0)
 
 #define MEMSET_LOOP_LIMIT  1024