[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
diff --git a/libcxx/test/std/atomics/atomics.flag/clear.pass.cpp b/libcxx/test/std/atomics/atomics.flag/clear.pass.cpp
index 7c93626..ea5ae45 100644
--- a/libcxx/test/std/atomics/atomics.flag/clear.pass.cpp
+++ b/libcxx/test/std/atomics/atomics.flag/clear.pass.cpp
@@ -22,49 +22,49 @@
int main()
{
{
- std::atomic_flag f = ATOMIC_FLAG_INIT;
+ std::atomic_flag f(false);
f.test_and_set();
f.clear();
assert(f.test_and_set() == 0);
}
{
- std::atomic_flag f = ATOMIC_FLAG_INIT;
+ std::atomic_flag f(false);
f.test_and_set();
f.clear(std::memory_order_relaxed);
assert(f.test_and_set() == 0);
}
{
- std::atomic_flag f = ATOMIC_FLAG_INIT;
+ std::atomic_flag f(false);
f.test_and_set();
f.clear(std::memory_order_release);
assert(f.test_and_set() == 0);
}
{
- std::atomic_flag f = ATOMIC_FLAG_INIT;
+ std::atomic_flag f(false);
f.test_and_set();
f.clear(std::memory_order_seq_cst);
assert(f.test_and_set() == 0);
}
{
- volatile std::atomic_flag f = ATOMIC_FLAG_INIT;
+ volatile std::atomic_flag f(false);
f.test_and_set();
f.clear();
assert(f.test_and_set() == 0);
}
{
- volatile std::atomic_flag f = ATOMIC_FLAG_INIT;
+ volatile std::atomic_flag f(false);
f.test_and_set();
f.clear(std::memory_order_relaxed);
assert(f.test_and_set() == 0);
}
{
- volatile std::atomic_flag f = ATOMIC_FLAG_INIT;
+ volatile std::atomic_flag f(false);
f.test_and_set();
f.clear(std::memory_order_release);
assert(f.test_and_set() == 0);
}
{
- volatile std::atomic_flag f = ATOMIC_FLAG_INIT;
+ volatile std::atomic_flag f(false);
f.test_and_set();
f.clear(std::memory_order_seq_cst);
assert(f.test_and_set() == 0);