diff --git a/mercurial/thirdparty/xdiff/xutils.c b/mercurial/thirdparty/xdiff/xutils.c
--- a/mercurial/thirdparty/xdiff/xutils.c
+++ b/mercurial/thirdparty/xdiff/xutils.c
@@ -303,12 +303,16 @@
 
 unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
 	XXH32_hash_t h;
-	char const *ptr = *data;
+	char const *ptr;
 
 	if (flags & XDF_WHITESPACE_FLAGS)
 		return xdl_hash_record_with_whitespace(data, top, flags);
 
-	for (; ptr < top && *ptr != '\n'; ptr++) { }
+	ptr = memchr(*data, '\n', top - *data + 1);
+	if (!ptr) {
+		ptr = top;
+	}
+
 	h = XDIFF_XXH32(*data, ptr - *data + 1, 0);
 	*data = ptr < top ? ptr + 1: ptr;
 	return h;