C++11 atomics

base/atomicops.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // For atomic operations on reference counts, see atomic_refcount.h.
 // For atomic operations on sequence numbers, see atomic_sequence_num.h.
 
 // The routines exported by this module are subtle.  If you use them, even if
 // you get the code right, it will depend on careful reasoning about atomicity
 // and memory ordering; it will be less readable, and harder to maintain.  If
@@ skipping 126 matching lines @@
 void Acquire_Store(volatile Atomic64* ptr, Atomic64 value);
 void Release_Store(volatile Atomic64* ptr, Atomic64 value);
 Atomic64 NoBarrier_Load(volatile const Atomic64* ptr);
 Atomic64 Acquire_Load(volatile const Atomic64* ptr);
 Atomic64 Release_Load(volatile const Atomic64* ptr);
 #endif  // ARCH_CPU_64_BITS
 
 }  // namespace subtle
 }  // namespace base
 
-// Try to use a portable implementation based on C++11 atomics.
-//
-// Some toolchains support C++11 language features without supporting library
-// features (recent compiler, older STL). Whitelist libstdc++ and libc++ that we
-// know will have <atomic> when compiling C++11.
-#if ((__cplusplus >= 201103L) &&                            \
-     ((defined(__GLIBCXX__) && (__GLIBCXX__ > 20110216)) || \
-      (defined(_LIBCPP_VERSION) && (_LIBCPP_STD_VER >= 11))))
+#if (defined(OS_WIN) && defined(COMPILER_MSVC) && \

[Nico, 2015/12/07 03:55:58]

OS_WIN implies COMPILER_MSVC, remove the COMPILER_MSVC bit

[JF, 2015/12/07 04:23:31]

That's true when using LLVM on Windows as well? I'll do the change, we can put
back MSVC if not.

[Nico, 2015/12/07 04:58:28]

Yes. Just like clang defines__gnuc__ when using the GCC compatible driver, it
defines _MSc_ver when using the cl compatible driver.

+     defined(ARCH_CPU_X86_FAMILY))

[Nico, 2015/12/07 03:55:58]

We don't have a win/arm build either, so you can get rid of this too I think

…oh, this is copied from the lhs. Then it's fine as-is I suppose, but I'd
simplify it while here. Up to you.

[JF, 2015/12/07 04:23:31]

Removed, you're right it shouldn't have been there in the first place. Maybe
someone was too hopeful about Windows RT :-)

+// TODO(jfb): The MSVC header includes windows.h, which other files end up
+//            relying on. Fix this as part of crbug.com/559247.
+#  include "base/atomicops_internals_x86_msvc.h"
+#else
 #  include "base/atomicops_internals_portable.h"
-#else  // Otherwise use a platform specific implementation.
-#  if defined(THREAD_SANITIZER)
-#    error "Thread sanitizer must use the portable atomic operations"
-#  elif (defined(OS_WIN) && defined(COMPILER_MSVC) && \
-         defined(ARCH_CPU_X86_FAMILY))
-#    include "base/atomicops_internals_x86_msvc.h"
-#  elif defined(OS_MACOSX)
-#    include "base/atomicops_internals_mac.h"
-#  else
-#    error "Atomic operations are not supported on your platform"
-#  endif
-#endif   // Portable / non-portable includes.
+#endif
 
 // On some platforms we need additional declarations to make
 // AtomicWord compatible with our other Atomic* types.
 #if defined(OS_MACOSX) || defined(OS_OPENBSD)
 #include "base/atomicops_internals_atomicword_compat.h"
 #endif
 
 #endif  // BASE_ATOMICOPS_H_