diff mercurial/parsers.c @ 15033:2ef2d3a5cd2d stable

parsers: avoid pointer aliasing

Newer versions of GCC have aggressive pointer alias optimizations that
might get fooled by our pointer manipulations. These issues shouldn't
be encountered in practice because distutils compiles extensions with
-fno-strict-alias but the code was not valid according to the standard.

--- a/mercurial/parsers.c	Wed Aug 10 13:25:35 2011 -0500
+++ b/mercurial/parsers.c	Wed Aug 10 13:40:01 2011 -0500
@@ -170,7 +170,7 @@
 	int state, mode, size, mtime;
 	unsigned int flen;
 	int len;
-	char decode[16]; /* for alignment */
+	uint32_t decode[4]; /* for alignment */
 
 	if (!PyArg_ParseTuple(args, "O!O!s#:parse_dirstate",
 			      &PyDict_Type, &dmap,
@@ -194,10 +194,10 @@
 		/* unpack header */
 		state = *cur;
 		memcpy(decode, cur + 1, 16);
-		mode = ntohl(*(uint32_t *)(decode));
-		size = ntohl(*(uint32_t *)(decode + 4));
-		mtime = ntohl(*(uint32_t *)(decode + 8));
-		flen = ntohl(*(uint32_t *)(decode + 12));
+		mode = ntohl(decode[0]);
+		size = ntohl(decode[1]);
+		mtime = ntohl(decode[2]);
+		flen = ntohl(decode[3]);
 		cur += 17;
 		if (cur + flen > end || cur + flen < cur) {
 			PyErr_SetString(PyExc_ValueError, "overflow in dirstate");
@@ -264,27 +264,27 @@
 	int comp_len, uncomp_len, base_rev, link_rev, parent_1, parent_2;
 	const char *c_node_id;
 	const char *end = data + size;
-	char decode[64]; /* to enforce alignment with inline data */
+	uint32_t decode[8]; /* to enforce alignment with inline data */
 
 	while (data < end) {
 		unsigned int step;
 
-		memcpy(decode, data, 64);
-		offset_flags = ntohl(*((uint32_t *) (decode + 4)));
+		memcpy(decode, data, 32);
+		offset_flags = ntohl(decode[1]);
 		if (n == 0) /* mask out version number for the first entry */
 			offset_flags &= 0xFFFF;
 		else {
-			uint32_t offset_high =  ntohl(*((uint32_t *)decode));
+			uint32_t offset_high =  ntohl(decode[0]);
 			offset_flags |= ((uint64_t)offset_high) << 32;
 		}
 
-		comp_len = ntohl(*((uint32_t *)(decode + 8)));
-		uncomp_len = ntohl(*((uint32_t *)(decode + 12)));
-		base_rev = ntohl(*((uint32_t *)(decode + 16)));
-		link_rev = ntohl(*((uint32_t *)(decode + 20)));
-		parent_1 = ntohl(*((uint32_t *)(decode + 24)));
-		parent_2 = ntohl(*((uint32_t *)(decode + 28)));
-		c_node_id = decode + 32;
+		comp_len = ntohl(decode[2]);
+		uncomp_len = ntohl(decode[3]);
+		base_rev = ntohl(decode[4]);
+		link_rev = ntohl(decode[5]);
+		parent_1 = ntohl(decode[6]);
+		parent_2 = ntohl(decode[7]);
+		c_node_id = data + 32;
 
 		entry = Py_BuildValue("Liiiiiis#", offset_flags, comp_len,
 			      uncomp_len, base_rev, link_rev,