https://gcc.gnu.org/g:a6ffae6d7f0fb4515103a5f056b691301988268d
commit r17-352-ga6ffae6d7f0fb4515103a5f056b691301988268d Author: Jonathan Wakely <[email protected]> Date: Thu Apr 30 16:06:11 2026 +0100 libstdc++: Use hardware_destructive_interference_size in atomic.cc This code was moved from a header into the library, so is no longer affected by compiler options used when including the headers. We can just use std::hardware_destructive_interference_size now, and remove the comment. libstdc++-v3/ChangeLog: * src/c++20/atomic.cc (__waitable_state::_S_align): Remove. (__waitable_state::_M_waiters, __waitable_state::_M_ver): Use std::hardware_destructive_interference_size for alignment. Reviewed-by: Tomasz Kamiński <[email protected]> Diff: --- libstdc++-v3/src/c++20/atomic.cc | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/libstdc++-v3/src/c++20/atomic.cc b/libstdc++-v3/src/c++20/atomic.cc index 3e02f437db3c..3fbc05c2e682 100644 --- a/libstdc++-v3/src/c++20/atomic.cc +++ b/libstdc++-v3/src/c++20/atomic.cc @@ -289,12 +289,9 @@ namespace // The state used by atomic waiting and notifying functions. struct __waitable_state { - // Don't use std::hardware_destructive_interference_size here because we - // don't want the layout of library types to depend on compiler options. - static constexpr auto _S_align = 64; - // Count of threads blocked waiting on this state. - alignas(_S_align) __platform_wait_t _M_waiters = 0; + alignas(std::hardware_destructive_interference_size) + __platform_wait_t _M_waiters = 0; #ifndef _GLIBCXX_HAVE_PLATFORM_WAIT mutex _M_mtx; @@ -310,7 +307,8 @@ namespace // If we can't do a platform wait on the atomic variable itself, // we use this member as a proxy for the atomic variable and we // use this for waiting and notifying functions instead. - alignas(_S_align) __platform_wait_t _M_ver = 0; + alignas(std::hardware_destructive_interference_size) + __platform_wait_t _M_ver = 0; #ifndef _GLIBCXX_HAVE_PLATFORM_WAIT __condvar _M_cv;
