From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 18 Jul 2005 15:55:01 +0000 (+0000)
Subject: MemSet() must not cast its pointer argument to int32* until after it has
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=08e34088772d0aaeb0eed8eb620a899397510d66;p=users%2Fbernd%2Fpostgres.git

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 a7e6aac425..3fc0093980 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -560,21 +560,22 @@ 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 * _stop = (int32 *) ((char *) _start + _len); \
+			int32 *_start = (int32 *) _vstart; \
+			int32 *_stop = (int32 *) ((char *) _start + _len); \
 			while (_start < _stop) \
 				*_start++ = 0; \
 		} \
 		else \
-			memset((char *) _start, _val, _len); \
+			memset(_vstart, _val, _len); \
 	} while (0)
 
 #define MEMSET_LOOP_LIMIT  64