Merge branch 'atomic-take2' into 'master'

atomic: Fix type check of g_atomic_pointer_compare_and_exchange()

See merge request GNOME/glib!1919

1 files changed, 20 insertions, 0 deletions

diff --git a/glib/gatomic.h b/glib/gatomic.h
index 12387df26..3b84a5049 100644
--- a/glib/gatomic.h
+++ b/glib/gatomic.h
@@ -182,6 +182,25 @@ G_END_DECLS
     (void) (0 ? *(atomic) ^ (val) : 1);                                      \
     (guint) __atomic_fetch_xor ((atomic), (val), __ATOMIC_SEQ_CST);          \
   }))
+
+#if defined(glib_typeof) && defined(__cplusplus) && __cplusplus >= 201103L
+/* This is typesafe because we check we can assign oldval to the type of
+ * (*atomic). Unfortunately it can only be done in C++ because gcc/clang warn
+ * when atomic is volatile and not oldval, or when atomic is gsize* and oldval
+ * is NULL. Note that clang++ force us to be typesafe because it is an error if the 2nd
+ * argument of __atomic_compare_exchange_n() has a different type than the
+ * first.
+ * https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1919
+ * https://gitlab.gnome.org/GNOME/glib/-/merge_requests/1715#note_1024120. */
+#define g_atomic_pointer_compare_and_exchange(atomic, oldval, newval) \
+  (G_GNUC_EXTENSION ({                                                       \
+    G_STATIC_ASSERT (sizeof (oldval) == sizeof (gpointer));                  \
+    glib_typeof (*(atomic)) gapcae_oldval = (oldval);                        \
+    G_STATIC_ASSERT (sizeof *(atomic) == sizeof (gpointer));                 \
+    (void) (0 ? (gpointer) *(atomic) : NULL);                                \
+    __atomic_compare_exchange_n ((atomic), &gapcae_oldval, (newval), FALSE, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ? TRUE : FALSE; \
+  }))
+#else /* if !(defined(glib_typeof) && defined(__cplusplus) && __cplusplus >= 201103L) */
 #define g_atomic_pointer_compare_and_exchange(atomic, oldval, newval) \
   (G_GNUC_EXTENSION ({                                                       \
     G_STATIC_ASSERT (sizeof (oldval) == sizeof (gpointer));                  \
@@ -190,6 +209,7 @@ G_END_DECLS
     (void) (0 ? (gpointer) *(atomic) : NULL);                                \
     __atomic_compare_exchange_n ((atomic), &gapcae_oldval, (newval), FALSE, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) ? TRUE : FALSE; \
   }))
+#endif /* defined(glib_typeof) */
 #define g_atomic_pointer_add(atomic, val) \
   (G_GNUC_EXTENSION ({                                                       \
     G_STATIC_ASSERT (sizeof *(atomic) == sizeof (gpointer));                 \