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| author | Eric Fiselier <eric@efcs.ca> | 2015-08-19 17:21:46 +0000 |
|---|---|---|
| committer | Eric Fiselier <eric@efcs.ca> | 2015-08-19 17:21:46 +0000 |
| commit | 749adeba3d655f27abec2a3589a612a15d8be21c (patch) | |
| tree | 6c7de9eac62b2185c5754850d02f5425de00f659 /libcxx/src/ios.cpp | |
| parent | 24b64a940579cbdb33554be5eeff8b9f6a0a331a (diff) | |
[libcxx] Allow use of <atomic> in C++03. Try 3.
Summary:
After putting this question up on cfe-dev I have decided that it would be best to allow the use of `<atomic>` in C++03. Although static initialization is a concern the syntax required to get it is C++11 only. Meaning that C++11 constant static initialization cannot silently break in C++03, it will always cause a syntax error. Furthermore `ATOMIC_VAR_INIT` and `ATOMIC_FLAG_INIT` remain defined in C++03 even though they cannot be used because C++03 usages will cause better error messages.
The main change in this patch is to replace `__has_feature(cxx_atomic)`, which only returns true when C++ >= 11, to `__has_extension(c_atomic)` which returns true whenever clang supports the required atomic builtins.
This patch adds the following macros:
* `_LIBCPP_HAS_C_ATOMIC_IMP` - Defined on clang versions which provide the C `_Atomic` keyword.
* `_LIBCPP_HAS_GCC_ATOMIC_IMP` - Defined on GCC > 4.7. We must use the fallback atomic implementation.
* `_LIBCPP_HAS_NO_ATOMIC_HEADER` - Defined when it is not safe to include `<atomic>`.
`_LIBCPP_HAS_C_ATOMIC_IMP` and `_LIBCPP_HAS_GCC_ATOMIC_IMP` are mutually exclusive, only one should be defined. If neither is defined then `<atomic>` is not implemented and including `<atomic>` will issue an error.
Reviewers: chandlerc, jroelofs, mclow.lists
Subscribers: cfe-commits
Differential Revision: http://reviews.llvm.org/D11555
llvm-svn: 245463
Diffstat (limited to 'libcxx/src/ios.cpp')
| -rw-r--r-- | libcxx/src/ios.cpp | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/libcxx/src/ios.cpp b/libcxx/src/ios.cpp index 9d9daa99adc1..23e3ee0ca044 100644 --- a/libcxx/src/ios.cpp +++ b/libcxx/src/ios.cpp @@ -152,7 +152,7 @@ ios_base::getloc() const } // xalloc -#if __has_feature(cxx_atomic) && !defined(_LIBCPP_HAS_NO_THREADS) +#if defined(_LIBCPP_HAS_C_ATOMIC_IMP) && !defined(_LIBCPP_HAS_NO_THREADS) atomic<int> ios_base::__xindex_ = ATOMIC_VAR_INIT(0); #else int ios_base::__xindex_ = 0; |