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.

mercurial/mpatch.c

@@ -238,7 +238,7 b' static struct flist *decode(const char *'
 	struct flist *l;
 	struct frag *lt;
 	const char *data = bin + 12, *end = bin + len;
-	char decode[12]; /* for dealing with alignment issues */
+	uint32_t decode[3]; /* for dealing with alignment issues */
 
 	/* assume worst case size, we won't have many of these lists */
 	l = lalloc(len / 12);
@@ -249,9 +249,9 b' static struct flist *decode(const char *'
 
 	while (data <= end) {
 		memcpy(decode, bin, 12);
-		lt->start = ntohl(*(uint32_t *)decode);
-		lt->end = ntohl(*(uint32_t *)(decode + 4));
-		lt->len = ntohl(*(uint32_t *)(decode + 8));
+		lt->start = ntohl(decode[0]);
+		lt->end = ntohl(decode[1]);
+		lt->len = ntohl(decode[2]);
 		if (lt->start > lt->end)
 			break; /* sanity check */
 		bin = data + lt->len;
@@ -397,7 +397,7 b' patchedsize(PyObject *self, PyObject *ar'
 	long orig, start, end, len, outlen = 0, last = 0;
 	int patchlen;
 	char *bin, *binend, *data;
-	char decode[12]; /* for dealing with alignment issues */
+	uint32_t decode[3]; /* for dealing with alignment issues */
 
 	if (!PyArg_ParseTuple(args, "ls#", &orig, &bin, &patchlen))
 		return NULL;
@@ -407,9 +407,9 b' patchedsize(PyObject *self, PyObject *ar'
 
 	while (data <= binend) {
 		memcpy(decode, bin, 12);
-		start = ntohl(*(uint32_t *)decode);
-		end = ntohl(*(uint32_t *)(decode + 4));
-		len = ntohl(*(uint32_t *)(decode + 8));
+		start = ntohl(decode[0]);
+		end = ntohl(decode[1]);
+		len = ntohl(decode[2]);
 		if (start > end)
 			break; /* sanity check */
 		bin = data + len;

mercurial/parsers.c

@@ -170,7 +170,7 b' static PyObject *parse_dirstate(PyObject'
 	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 b' static PyObject *parse_dirstate(PyObject'
 		/* 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 b' static int _parse_index_ng(const char *d'
 	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,