1 files changed, 19 insertions, 0 deletions
diff --git a/lib/builtins/atomic_flag_test_and_set.c b/lib/builtins/atomic_flag_test_and_set.c
new file mode 100644
index 0000000..07209fc
--- /dev/null
+++ b/lib/builtins/atomic_flag_test_and_set.c
@@ -0,0 +1,19 @@
+/*===-- atomic_flag_test_and_set.c ------------------------------------------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ *===------------------------------------------------------------------------===
+ *
+ * This file implements atomic_flag_test_and_set from C11's stdatomic.h.
+ *
+ *===------------------------------------------------------------------------===
+ */
+
+#include <stdatomic.h>
+#undef atomic_flag_test_and_set
+_Bool atomic_flag_test_and_set(volatile atomic_flag *object) {
+  return __c11_atomic_exchange(&(object)->_Value, 1, __ATOMIC_SEQ_CST);
+}