https://gcc.gnu.org/g:57a8b54cc4d9d7750d8e98f1df1cbbb1aacfad09
commit r17-363-g57a8b54cc4d9d7750d8e98f1df1cbbb1aacfad09 Author: Jonathan Wakely <[email protected]> Date: Tue May 5 13:54:02 2026 +0100 libstdc++: Simplify std::shared_ptr internals Now that we don't use the EBO we can flatten the _Sp_counted_deleter and _Sp_counted_ptr_inplace layouts by removing their _Impl classes. libstdc++-v3/ChangeLog: * include/bits/out_ptr.h (out_ptr_t::_Impl::~_Impl): Adjust access to shared_ptr internals. * include/bits/shared_ptr_base.h (_Sp_counted_deleter): Remove _Impl class and replace _M_impl with the data members it contained. (_Sp_counted_ptr_inplace): Likewise. Reviewed-by: Tomasz Kamiński <[email protected]> Diff: --- libstdc++-v3/include/bits/out_ptr.h | 2 +- libstdc++-v3/include/bits/shared_ptr_base.h | 60 ++++++++--------------------- 2 files changed, 18 insertions(+), 44 deletions(-) diff --git a/libstdc++-v3/include/bits/out_ptr.h b/libstdc++-v3/include/bits/out_ptr.h index cc5a8a3adacb..f5fdc6cf910f 100644 --- a/libstdc++-v3/include/bits/out_ptr.h +++ b/libstdc++-v3/include/bits/out_ptr.h @@ -257,7 +257,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION auto& __pi = _M_smart._M_refcount._M_pi; if (_Sp __ptr = _M_smart.get()) - static_cast<_Scd*>(__pi)->_M_impl._M_ptr = __ptr; + static_cast<_Scd*>(__pi)->_M_ptr = __ptr; else // Destroy the control block manually without invoking deleter. std::__exchange(__pi, nullptr)->_M_destroy(); } diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h index 4a8c67703999..7366f1e04702 100644 --- a/libstdc++-v3/include/bits/shared_ptr_base.h +++ b/libstdc++-v3/include/bits/shared_ptr_base.h @@ -547,32 +547,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Ptr, typename _Deleter, typename _Alloc, _Lock_policy _Lp> class _Sp_counted_deleter final : public _Sp_counted_base<_Lp> { - class _Impl - { - [[__no_unique_address__]] _Sp_ebo_helper<_Deleter> _M_d; - [[__no_unique_address__]] _Sp_ebo_helper<_Alloc> _M_a; - - public: - _Impl(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept - : _M_d{std::move(__d)}, _M_a{__a}, _M_ptr(__p) - { } - - _Deleter& _M_del() noexcept { return _M_d._M_obj; } - _Alloc& _M_alloc() noexcept { return _M_a._M_obj; } - - _Ptr _M_ptr; - }; - public: using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_deleter>; // __d(__p) must not throw. _Sp_counted_deleter(_Ptr __p, _Deleter __d) noexcept - : _M_impl(__p, std::move(__d), _Alloc()) { } + : _M_del{std::move(__d)}, _M_alloc{}, _M_ptr(__p) { } // __d(__p) must not throw. _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept - : _M_impl(__p, std::move(__d), __a) { } + : _M_del{std::move(__d)}, _M_alloc{__a}, _M_ptr(__p) { } #pragma GCC diagnostic push // PR tree-optimization/122197 #pragma GCC diagnostic ignored "-Wfree-nonheap-object" @@ -582,12 +566,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION virtual void _M_dispose() noexcept - { _M_impl._M_del()(_M_impl._M_ptr); } + { _M_del._M_obj(_M_ptr); } virtual void _M_destroy() noexcept { - __allocator_type __a(_M_impl._M_alloc()); + __allocator_type __a(_M_alloc._M_obj); __allocated_ptr<__allocator_type> __guard_ptr{ __a, this }; this->~_Sp_counted_deleter(); } @@ -598,19 +582,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #if __cpp_rtti // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2400. shared_ptr's get_deleter() should use addressof() - return __ti == typeid(_Deleter) - ? std::__addressof(_M_impl._M_del()) - : nullptr; -#else - return nullptr; + if (__ti == typeid(_Deleter)) + return std::__addressof(_M_del._M_obj); #endif + return nullptr; } private: #ifdef __glibcxx_out_ptr template<typename, typename, typename...> friend class out_ptr_t; #endif - _Impl _M_impl; + + [[__no_unique_address__]] _Sp_ebo_helper<_Deleter> _M_del; + [[__no_unique_address__]] _Sp_ebo_helper<_Alloc> _M_alloc; + _Ptr _M_ptr; }; // helpers for make_shared / allocate_shared @@ -640,25 +625,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Tp, typename _Alloc, _Lock_policy _Lp> class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp> { - class _Impl - { - [[__no_unique_address__]] _Sp_ebo_helper<_Alloc> _M_a; - - public: - explicit _Impl(_Alloc __a) noexcept : _M_a{std::move(__a)} { } - - _Alloc& _M_alloc() noexcept { return _M_a._M_obj; } - - __gnu_cxx::__aligned_buffer<__remove_cv_t<_Tp>> _M_storage; - }; - public: using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>; // Alloc parameter is not a reference so doesn't alias anything in __args template<typename... _Args> _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args) - : _M_impl(__a) + : _M_alloc{__a} { // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2070. allocate_shared should use allocator_traits<A>::construct @@ -674,14 +647,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION virtual void _M_dispose() noexcept { - allocator_traits<_Alloc>::destroy(_M_impl._M_alloc(), _M_ptr()); + allocator_traits<_Alloc>::destroy(_M_alloc._M_obj, _M_ptr()); } // Override because the allocator needs to know the dynamic type virtual void _M_destroy() noexcept { - __allocator_type __a(_M_impl._M_alloc()); + __allocator_type __a(_M_alloc._M_obj); __allocated_ptr<__allocator_type> __guard_ptr{ __a, this }; this->~_Sp_counted_ptr_inplace(); } @@ -711,9 +684,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } __remove_cv_t<_Tp>* - _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); } + _M_ptr() noexcept { return _M_storage._M_ptr(); } - _Impl _M_impl; + [[__no_unique_address__]] _Sp_ebo_helper<_Alloc> _M_alloc; + __gnu_cxx::__aligned_buffer<__remove_cv_t<_Tp>> _M_storage; }; #ifdef __glibcxx_smart_ptr_for_overwrite // C++ >= 20 && HOSTED
