Fix GC_unreachable_finalize_mark_proc to ensure its unique address

Even GC_unreachable_finalize_mark_proc and GC_normal_finalize_mark_proc
have identical behavior, their addresses should be guaranteed to be
distinct despite any potential compiler optimization.

* finalize.c (GC_unreachable_finalize_mark_proc): Add a dummy statement
before GC_normal_finalize_mark_proc() call; add comment.

1 files changed, 5 insertions, 0 deletions

diff --git a/finalize.c b/finalize.c
index 10c6ffb5..a065a964 100644
--- a/finalize.c
+++ b/finalize.c
@@ -657,6 +657,11 @@ STATIC void GC_null_finalize_mark_proc(ptr_t p)
 /* other objects specify no ordering.                                   */
 STATIC void GC_unreachable_finalize_mark_proc(ptr_t p)
 {
+    /* A dummy comparison to ensure the compiler not to optimize two    */
+    /* identical functions into a single one (thus, to ensure a unique  */
+    /* address of each).  Alternatively, GC_noop1(p) could be used.     */
+    if (EXPECT(NULL == p, FALSE)) return;
+
     GC_normal_finalize_mark_proc(p);
 }