Use AO primitive in GC_noop1 instead of no_sanitize attribute

This eliminates GCC TSan report about data race in GC_noop1.

* mark.c [AO_HAVE_store && THREAD_SANITIZER] (GC_noop_sink): Use AO_t
type instead of word.
* mark.c (GC_noop1): Remove GC_ATTR_NO_SANITIZE_THREAD; refine comment.
* mark.c [AO_HAVE_store && THREAD_SANITIZER] (GC_noop1): Use AO_store.

1 files changed, 12 insertions, 3 deletions

diff --git a/mark.c b/mark.c
index 5aab28e4..8e0f3c03 100644
--- a/mark.c
+++ b/mark.c
@@ -48,13 +48,22 @@ void GC_noop6(word arg1 GC_ATTR_UNUSED, word arg2 GC_ATTR_UNUSED,
 # endif
 }
 
-volatile word GC_noop_sink;
+#if defined(AO_HAVE_store) && defined(THREAD_SANITIZER)
+  volatile AO_t GC_noop_sink;
+#else
+  volatile word GC_noop_sink;
+#endif
 
-/* Single argument version, robust against whole program analysis. */
-GC_ATTR_NO_SANITIZE_THREAD
+/* Make the argument appear live to compiler.  This is similar  */
+/* to GC_noop6(), but with a single argument.  Robust against   */
+/* whole program analysis.                                      */
 GC_API void GC_CALL GC_noop1(word x)
 {
+# if defined(AO_HAVE_store) && defined(THREAD_SANITIZER)
+    AO_store(&GC_noop_sink, (AO_t)x);
+# else
     GC_noop_sink = x;
+# endif
 }
 
 /* Initialize GC_obj_kinds properly and standard free lists properly.   */