Eliminate 'value exceeds maximum object size' gcc warning in debug_malloc

Issue #406 (bdwgc).

* dbg_mlc.c [_FORTIFY_SOURCE && !__clang__] (GC_debug_malloc): Expand
SIZET_SAT_ADD() manually changing it to return GC_SIZE_MAX>>1 in case
of addition overflow; add comment.

1 files changed, 7 insertions, 1 deletions

diff --git a/dbg_mlc.c b/dbg_mlc.c
index 14db8fe3..b333a128 100644
--- a/dbg_mlc.c
+++ b/dbg_mlc.c
@@ -539,7 +539,13 @@ GC_API GC_ATTR_MALLOC void * GC_CALL GC_debug_malloc(size_t lb,
     /* Note that according to malloc() specification, if size is 0 then */
     /* malloc() returns either NULL, or a unique pointer value that can */
     /* later be successfully passed to free(). We always do the latter. */
-    result = GC_malloc(SIZET_SAT_ADD(lb, DEBUG_BYTES));
+#   if defined(_FORTIFY_SOURCE) && !defined(__clang__)
+      /* Workaround to avoid "exceeds maximum object size" gcc warning. */
+      result = GC_malloc(lb < GC_SIZE_MAX - DEBUG_BYTES ? lb + DEBUG_BYTES
+                                                        : GC_SIZE_MAX >> 1);
+#   else
+      result = GC_malloc(SIZET_SAT_ADD(lb, DEBUG_BYTES));
+#   endif
 #   ifdef GC_ADD_CALLER
       if (s == NULL) {
         GC_caller_func_offset(ra, &s, &i);