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Obey [atomics.types.operations.req]/21 for GCC.

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Summary:
Excerpt from [atomics.types.operations.req]/21:

> When only one memory_order argument is supplied, the value of
> success is order, and the value of failure is order except that a
> value of memory_order_acq_rel shall be replaced by the value
> memory_order_acquire and a value of memory_order_release shall be
> replaced by the value memory_order_relaxed.

Clean up some copy pasta while I'm here (someone added a return
statement to a void function).

Reviewers: EricWF, jroelofs, mclow.lists

Reviewed By: mclow.lists

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D6632

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@225280 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Albert
2015-01-06 18:39:37 +00:00
parent 656850f03e
commit c101738156
2 changed files with 57 additions and 6 deletions
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41
test/atomics/atomics.general/replace_failure_order.pass.cpp Normal file
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//===----------------------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// This test verifies behavior specified by [atomics.types.operations.req]/21:
//
// When only one memory_order argument is supplied, the value of success is
// order, and the value of failure is order except that a value of
// memory_order_acq_rel shall be replaced by the value memory_order_acquire
// and a value of memory_order_release shall be replaced by the value
// memory_order_relaxed.
//
// Clang's atomic intrinsics do this for us, but GCC's do not. We don't actually
// have visibility to see what these memory orders are lowered to, but we can at
// least check that they are lowered at all (otherwise there is a compile
// failure with GCC).
#include <atomic>
int main() {
std::atomic<int> i;
volatile std::atomic<int> v;
int exp;
i.compare_exchange_weak(exp, 0, std::memory_order_acq_rel);
i.compare_exchange_weak(exp, 0, std::memory_order_release);
i.compare_exchange_strong(exp, 0, std::memory_order_acq_rel);
i.compare_exchange_strong(exp, 0, std::memory_order_release);
v.compare_exchange_weak(exp, 0, std::memory_order_acq_rel);
v.compare_exchange_weak(exp, 0, std::memory_order_release);
v.compare_exchange_strong(exp, 0, std::memory_order_acq_rel);
v.compare_exchange_strong(exp, 0, std::memory_order_release);
return 0;
}