diff options
Diffstat (limited to 'libstdc++-v3/include/std/atomic')
| -rw-r--r-- | libstdc++-v3/include/std/atomic | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic index 1a17427e231..125e37a2838 100644 --- a/libstdc++-v3/include/std/atomic +++ b/libstdc++-v3/include/std/atomic @@ -165,7 +165,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION struct atomic { private: - _Tp _M_i; + // Align 1/2/4/8/16-byte types to at least their size. + static constexpr int _S_min_alignment + = (sizeof(_Tp) & (sizeof(_Tp) - 1)) || sizeof(_Tp) > 16 + ? 0 : sizeof(_Tp); + + static constexpr int _S_alignment + = _S_min_alignment > alignof(_Tp) ? _S_min_alignment : alignof(_Tp); + + alignas(_S_alignment) _Tp _M_i; static_assert(__is_trivially_copyable(_Tp), "std::atomic requires a trivially copyable type"); @@ -198,11 +206,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION bool is_lock_free() const noexcept - { return __atomic_is_lock_free(sizeof(_M_i), nullptr); } + { + // Produce a fake, minimally aligned pointer. + void *__a = reinterpret_cast<void *>(-__alignof(_M_i)); + return __atomic_is_lock_free(sizeof(_M_i), __a); + } bool is_lock_free() const volatile noexcept - { return __atomic_is_lock_free(sizeof(_M_i), nullptr); } + { + // Produce a fake, minimally aligned pointer. + void *__a = reinterpret_cast<void *>(-__alignof(_M_i)); + return __atomic_is_lock_free(sizeof(_M_i), __a); + } void store(_Tp __i, memory_order __m = memory_order_seq_cst) noexcept |