My recent refactoring of enable_shared_from_this broke support for an obscure use case, where shared_ptr "owns" a pointer to function (and the deleter does something with it, like unregister a callback from a plugin).
The problem is simply that I made the new _M_enable_shared_from_this_with overloads take a const _Yp* parameter, so that _Yp would be deduced as the non-const type. That was just laziness, to save using remove_const on the type. But that breaks function pointers, because const _Yp* won't deduce a type like void(*)(), and so there is no viable overload of _M_enable_shared_from_this_with. The fix is just to use a parameter of _Yp* and then use remove_cv<_Yp> to get the unqualified type. I'm also adjusting a test which uses const_pointer_cast<X> to cast a shared_ptr<const X> to shared_ptr<X>, but the object it owns was born const so casting it away and accessing it as non-const is undefined. PR libstdc++/80229 * include/bits/shared_ptr_base.h (__shared_ptr::_M_enable_shared_from_this_with): Change parameters to non-const and then use remove_cv to get unqualified type. * testsuite/20_util/enable_shared_from_this/members/const.cc: Don't cast away constness on object created const. * testsuite/20_util/shared_ptr/cons/80229.cc: New test. Tested powerpc64le-linux, committed to trunk.
commit fc31b73a950f957b7b5df2b56cb9285fac3edcd3 Author: Jonathan Wakely <jwak...@redhat.com> Date: Tue Mar 28 01:50:14 2017 +0100 PR libstdc++/80229 restore support for shared_ptr<function type> PR libstdc++/80229 * include/bits/shared_ptr_base.h (__shared_ptr::_M_enable_shared_from_this_with): Change parameters to non-const and then use remove_cv to get unqualified type. * testsuite/20_util/enable_shared_from_this/members/const.cc: Don't cast away constness on object created const. * testsuite/20_util/shared_ptr/cons/80229.cc: New test. diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h index a203f42..c8d7f20 100644 --- a/libstdc++-v3/include/bits/shared_ptr_base.h +++ b/libstdc++-v3/include/bits/shared_ptr_base.h @@ -1363,17 +1363,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION struct __has_esft_base<_Yp, __void_t<__esft_base_t<_Yp>>> : __not_<is_array<_Tp>> { }; // No enable shared_from_this for arrays - template<typename _Yp> - typename enable_if<__has_esft_base<_Yp>::value>::type - _M_enable_shared_from_this_with(const _Yp* __p) noexcept + template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type> + typename enable_if<__has_esft_base<_Yp2>::value>::type + _M_enable_shared_from_this_with(_Yp* __p) noexcept { if (auto __base = __enable_shared_from_this_base(_M_refcount, __p)) - __base->_M_weak_assign(const_cast<_Yp*>(__p), _M_refcount); + __base->_M_weak_assign(const_cast<_Yp2*>(__p), _M_refcount); } - template<typename _Yp> - typename enable_if<!__has_esft_base<_Yp>::value>::type - _M_enable_shared_from_this_with(const _Yp*) noexcept + template<typename _Yp, typename _Yp2 = typename remove_cv<_Yp>::type> + typename enable_if<!__has_esft_base<_Yp2>::value>::type + _M_enable_shared_from_this_with(_Yp*) noexcept { } void* diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc index 0f77726..3f8a6a5 100644 --- a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc +++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc @@ -32,9 +32,9 @@ test01() { struct X : public std::enable_shared_from_this<X> { }; using CX = const X; - std::shared_ptr<CX> p(new X); + std::shared_ptr<CX> p(new CX); VERIFY( share_ownership(p->shared_from_this(), p) ); - p.reset(new CX); + p.reset(new X); VERIFY( share_ownership(p->shared_from_this(), p) ); auto p2 = std::const_pointer_cast<X>(p)->shared_from_this(); VERIFY( share_ownership(p2, p) ); diff --git a/libstdc++-v3/testsuite/20_util/shared_ptr/cons/80229.cc b/libstdc++-v3/testsuite/20_util/shared_ptr/cons/80229.cc new file mode 100644 index 0000000..7b89066 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/shared_ptr/cons/80229.cc @@ -0,0 +1,26 @@ +// Copyright (C) 2017 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// <http://www.gnu.org/licenses/>. + +// { dg-do compile { target c++11 } } + +#include <memory> + +// PR libstdc++/80229 + +void del(void(*)()); +void the_func(); +std::shared_ptr<void()> ee(&the_func, &del);