Subject: [PATCH] Read unaligned match buffers with memcpy

Byte buffers need not satisfy integer alignment or aliasing requirements.
GCC 16 with x86-64-v3 vectorizes the cast loads using aligned AVX reads,
causing a segmentation fault. Copy into local integers instead.

--- a/src/zopfli/lz77.c
+++ b/src/zopfli/lz77.c
@@ -302,13 +302,20 @@
   if (sizeof(size_t) == 8) {
     /* 8 checks at once per array bounds check (size_t is 64-bit). */
-    while (scan < safe_end && *((size_t*)scan) == *((size_t*)match)) {
+    while (scan < safe_end) {
+      size_t scan_word, match_word;
+      memcpy(&scan_word, scan, sizeof(scan_word));
+      memcpy(&match_word, match, sizeof(match_word));
+      if (scan_word != match_word) break;
       scan += 8;
       match += 8;
     }
   } else if (sizeof(unsigned int) == 4) {
     /* 4 checks at once per array bounds check (unsigned int is 32-bit). */
-    while (scan < safe_end
-        && *((unsigned int*)scan) == *((unsigned int*)match)) {
+    while (scan < safe_end) {
+      unsigned int scan_word, match_word;
+      memcpy(&scan_word, scan, sizeof(scan_word));
+      memcpy(&match_word, match, sizeof(match_word));
+      if (scan_word != match_word) break;
       scan += 4;
       match += 4;
     }