https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114865
--- Comment #18 from Jonathan Wakely <redi at gcc dot gnu.org> --- So maybe: diff --git a/libstdc++-v3/include/bits/atomic_base.h b/libstdc++-v3/include/bits/atomic_base.h index aa7374bb252..662cff39df5 100644 --- a/libstdc++-v3/include/bits/atomic_base.h +++ b/libstdc++-v3/include/bits/atomic_base.h @@ -956,7 +956,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION constexpr bool __maybe_has_padding() { -#if ! __has_builtin(__builtin_clear_padding) + // We cannot clear padding in the constructor for C++11, + // so return false here to disable all code for zeroing padding. +#if __cplusplus < 201402L || ! __has_builtin(__builtin_clear_padding) return false; #elif __has_builtin(__has_unique_object_representations) return !__has_unique_object_representations(_Tp) diff --git a/libstdc++-v3/include/std/atomic b/libstdc++-v3/include/std/atomic index 36ff89a146c..336f27832fc 100644 --- a/libstdc++-v3/include/std/atomic +++ b/libstdc++-v3/include/std/atomic @@ -238,6 +238,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION constexpr atomic(_Tp __i) noexcept : _M_i(__i) { + // A constexpr constructor must be empty in C++11, + // so we can only clear padding for C++14 and later. #if __cplusplus >= 201402L && __has_builtin(__builtin_clear_padding) if _GLIBCXX17_CONSTEXPR (__atomic_impl::__maybe_has_padding<_Tp>()) __builtin_clear_padding(std::__addressof(_M_i));