ovs-atomic: Add native Clang implementation.

With this implementation I get warnings with Clang on GNU/Linux when the
previous patch is not applied.  This ought to make it easier to avoid
introducing new problems in the future even without building on FreeBSD.

Signed-off-by: Ben Pfaff <[email protected]>
Acked-by: Jarno Rajahalme <[email protected]>

lib/automake.mk

@@ -127,6 +127,8 @@ lib_libopenvswitch_a_SOURCES = \
 	lib/ofpbuf.c \
 	lib/ofpbuf.h \
 	lib/ovs-atomic-c11.h \
+	lib/ovs-atomic-clang.h \
+	lib/ovs-atomic-flag-gcc4.7+.h \
 	lib/ovs-atomic-gcc4+.c \
 	lib/ovs-atomic-gcc4+.h \
 	lib/ovs-atomic-gcc4.7+.h \

lib/compiler.h

@@ -20,6 +20,9 @@
 #ifndef __has_feature
   #define __has_feature(x) 0
 #endif
+#ifndef __has_extension
+  #define __has_extension(x) 0
+#endif
 
 #if __GNUC__ && !__CHECKER__
 #define NO_RETURN __attribute__((__noreturn__))

lib/ovs-atomic-clang.h

@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2013 Nicira, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* This header implements atomic operation primitives on Clang. */
+#ifndef IN_OVS_ATOMIC_H
+#error "This header should only be included indirectly via ovs-atomic.h."
+#endif
+
+#define OVS_ATOMIC_CLANG_IMPL 1
+
+/* Standard atomic types. */
+typedef _Atomic(_Bool) atomic_bool;
+
+typedef _Atomic(char) atomic_char;
+typedef _Atomic(signed char) atomic_schar;
+typedef _Atomic(unsigned char) atomic_uchar;
+
+typedef _Atomic(short) atomic_short;
+typedef _Atomic(unsigned short) atomic_ushort;
+
+typedef _Atomic(int) atomic_int;
+typedef _Atomic(unsigned int) atomic_uint;
+
+typedef _Atomic(long) atomic_long;
+typedef _Atomic(unsigned long) atomic_ulong;
+
+typedef _Atomic(long long) atomic_llong;
+typedef _Atomic(unsigned long long) atomic_ullong;
+
+typedef _Atomic(size_t) atomic_size_t;
+typedef _Atomic(ptrdiff_t) atomic_ptrdiff_t;
+
+typedef _Atomic(intmax_t) atomic_intmax_t;
+typedef _Atomic(uintmax_t) atomic_uintmax_t;
+
+typedef _Atomic(intptr_t) atomic_intptr_t;
+typedef _Atomic(uintptr_t) atomic_uintptr_t;
+
+/* Nonstandard atomic types. */
+typedef _Atomic(uint8_t)   atomic_uint8_t;
+typedef _Atomic(uint16_t)  atomic_uint16_t;
+typedef _Atomic(uint32_t)  atomic_uint32_t;
+typedef _Atomic(uint64_t)  atomic_uint64_t;
+
+typedef _Atomic(int8_t)    atomic_int8_t;
+typedef _Atomic(int16_t)   atomic_int16_t;
+typedef _Atomic(int32_t)   atomic_int32_t;
+typedef _Atomic(int64_t)   atomic_int64_t;
+
+#define ATOMIC_VAR_INIT(VALUE) (VALUE)
+
+#define atomic_init(OBJECT, VALUE) __c11_atomic_init(OBJECT, VALUE)
+
+/* Clang hard-codes these exact values internally but does not appear to
+ * export any names for them. */
+typedef enum {
+    memory_order_relaxed = 0,
+    memory_order_consume = 1,
+    memory_order_acquire = 2,
+    memory_order_release = 3,
+    memory_order_acq_rel = 4,
+    memory_order_seq_cst = 5
+} memory_order;
+
+#define atomic_thread_fence(ORDER) __c11_atomic_thread_fence(ORDER)
+#define atomic_signal_fence(ORDER) __c11_atomic_signal_fence(ORDER)
+
+#define atomic_store(DST, SRC) \
+    atomic_store_explicit(DST, SRC, memory_order_seq_cst)
+#define atomic_store_explicit(DST, SRC, ORDER) \
+    __c11_atomic_store(DST, SRC, ORDER)
+
+
+#define atomic_read(SRC, DST) \
+    atomic_read_explicit(SRC, DST, memory_order_seq_cst)
+#define atomic_read_explicit(SRC, DST, ORDER)   \
+    (*(DST) = __c11_atomic_load(SRC, ORDER), \
+     (void) 0)
+
+#define atomic_add(RMW, ARG, ORIG) \
+    atomic_add_explicit(RMW, ARG, ORIG, memory_order_seq_cst)
+#define atomic_sub(RMW, ARG, ORIG) \
+    atomic_sub_explicit(RMW, ARG, ORIG, memory_order_seq_cst)
+#define atomic_or(RMW, ARG, ORIG) \
+    atomic_or_explicit(RMW, ARG, ORIG, memory_order_seq_cst)
+#define atomic_xor(RMW, ARG, ORIG) \
+    atomic_xor_explicit(RMW, ARG, ORIG, memory_order_seq_cst)
+#define atomic_and(RMW, ARG, ORIG) \
+    atomic_and_explicit(RMW, ARG, ORIG, memory_order_seq_cst)
+
+#define atomic_add_explicit(RMW, ARG, ORIG, ORDER) \
+    (*(ORIG) = __c11_atomic_fetch_add(RMW, ARG, ORDER), (void) 0)
+#define atomic_sub_explicit(RMW, ARG, ORIG, ORDER) \
+    (*(ORIG) = __c11_atomic_fetch_sub(RMW, ARG, ORDER), (void) 0)
+#define atomic_or_explicit(RMW, ARG, ORIG, ORDER) \
+    (*(ORIG) = __c11_atomic_fetch_or(RMW, ARG, ORDER), (void) 0)
+#define atomic_xor_explicit(RMW, ARG, ORIG, ORDER) \
+    (*(ORIG) = __c11_atomic_fetch_xor(RMW, ARG, ORDER), (void) 0)
+#define atomic_and_explicit(RMW, ARG, ORIG, ORDER) \
+    (*(ORIG) = __c11_atomic_fetch_and(RMW, ARG, ORDER), (void) 0)
+
+#include "ovs-atomic-flag-gcc4.7+.h"

lib/ovs-atomic-flag-gcc4.7+.h

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2013 Nicira, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* This header implements atomic_flag on Clang and on GCC 4.7 and later. */
+#ifndef IN_OVS_ATOMIC_H
+#error "This header should only be included indirectly via ovs-atomic.h."
+#endif
+
+/* atomic_flag */
+
+typedef struct {
+    unsigned char b;
+} atomic_flag;
+#define ATOMIC_FLAG_INIT { .b = false }
+
+static inline bool
+atomic_flag_test_and_set_explicit(volatile atomic_flag *object,
+                                  memory_order order)
+{
+    return __atomic_test_and_set(&object->b, order);
+}
+
+static inline bool
+atomic_flag_test_and_set(volatile atomic_flag *object)
+{
+    return atomic_flag_test_and_set_explicit(object, memory_order_seq_cst);
+}
+
+static inline void
+atomic_flag_clear_explicit(volatile atomic_flag *object, memory_order order)
+{
+    __atomic_clear(object, order);
+}
+
+static inline void
+atomic_flag_clear(volatile atomic_flag *object)
+{
+    atomic_flag_clear_explicit(object, memory_order_seq_cst);
+}

lib/ovs-atomic-gcc4.7+.h

@@ -107,35 +107,5 @@ typedef enum {
     (*(ORIG) = __atomic_fetch_xor(RMW, OPERAND, ORDER), (void) 0)
 #define atomic_and_explicit(RMW, OPERAND, ORIG, ORDER)  \
     (*(ORIG) = __atomic_fetch_and(RMW, OPERAND, ORDER), (void) 0)
-
-/* atomic_flag */
-
-typedef struct {
-    unsigned char b;
-} atomic_flag;
-#define ATOMIC_FLAG_INIT { .b = false }
-
-static inline bool
-atomic_flag_test_and_set_explicit(volatile atomic_flag *object,
-                                  memory_order order)
-{
-    return __atomic_test_and_set(&object->b, order);
-}
-
-static inline bool
-atomic_flag_test_and_set(volatile atomic_flag *object)
-{
-    return atomic_flag_test_and_set_explicit(object, memory_order_seq_cst);
-}
-
-static inline void
-atomic_flag_clear_explicit(volatile atomic_flag *object, memory_order order)
-{
-    __atomic_clear(object, order);
-}
-
-static inline void
-atomic_flag_clear(volatile atomic_flag *object)
-{
-    atomic_flag_clear_explicit(object, memory_order_seq_cst);
-}
+
+#include "ovs-atomic-flag-gcc4.7+.h"

lib/ovs-atomic.h

@@ -238,6 +238,8 @@
         #include "ovs-atomic-pthreads.h"
     #elif HAVE_STDATOMIC_H
         #include "ovs-atomic-c11.h"
+    #elif __has_extension(c_atomic)
+        #include "ovs-atomic-clang.h"
     #elif __GNUC__ >= 4 && __GNUC_MINOR__ >= 7
         #include "ovs-atomic-gcc4.7+.h"
     #elif HAVE_GCC4_ATOMICS