add atomic support (#261)

CMakeLists.txt

@@ -81,6 +81,7 @@ if(CMAKE_USE_PTHREADS_INIT)
 endif()
 
 add_definitions(
+  -DHAVE_ATOMIC
   -DHAVE_INET6
   -DHAVE_SELECT
   )

include/re_atomic.h

@@ -0,0 +1,37 @@
+/**
+ * @file re_atomic.h  Atomic support
+ *
+ * Copyright (C) 2022 Sebastian Reimers
+ */
+
+#ifndef RE_H_ATOMIC__
+#define RE_H_ATOMIC__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* C11 */
+#ifdef HAVE_ATOMIC
+#include <stdatomic.h>
+
+/* C99 */
+#elif defined(__clang__)
+#define __CLANG_ATOMICS
+
+#elif defined(__GNUC__)
+#if __GNUC_PREREQ(4, 9)
+#define __SYNC_ATOMICS
+#else
+#error "Atomic requires gcc >= 4.9"
+#endif /* __GNUC_PREREQ */
+
+#else
+#error "Your compiler does not support atomics"
+#endif /* HAVE_ATOMIC */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* RE_H_ATOMIC__ */

mk/re.mk

@@ -339,10 +339,9 @@ CFLAGS  += -std=c11
 HAVE_ATOMIC := 1
 endif
 
-CFLAGS  += -pedantic
-
 ifneq ($(HAVE_ATOMIC),)
 CFLAGS  += -DHAVE_ATOMIC
+CFLAGS  += -pedantic
 endif