PR libstdc++/88782 avoid ODR problems in std::make_shared
The old version of _Sp_counted_ptr_inplace::_M_get_deleter (up to GCC 8.2.0) expects to be passed a real std::typeinfo object, so mixing that with the new definition of the __shared_ptr constructor (which always passes the fake tag) leads to accessing the fake object as a real std::typeinfo. Instead of trying to make it safe to mix the old and new definitions, just stop using that function. By passing a reference to __shared_ptr::_M_ptr to the __shared_count constructor it can be set directly, without needing to obtain the pointer via the _M_get_deleter back-channel. This avoids a virtual dispatch (which fixes PR 87514). This means that code built against new libstdc++ headers doesn't use _M_get_deleter at all, and so make_shared works the same whether RTTI is enabled or not. Also change _M_get_deleter so that it checks for a real type_info object even when RTTI is disabled, by calling a library function. Unless libstdc++ itself is built without RTTI that library function will be able to test if it's the right type_info. This means the new definition of _M_get_deleter can handle both the fake type_info tag and a real type_info object, even if built without RTTI. If linking to objects built against older versions of libstdc++ then if all objects use -frtti or all use -fno-rtti, then the caller of _M_get_deleter and the definition of _M_get_deleter will be consistent and it will work. If mixing -frtti with -fno-rtti it can still fail if the linker picks an old definition of _M_get_deleter and an old __shared_ptr constructor that are incompatible. In that some or all objects might need to be recompiled. PR libstdc++/87514 PR libstdc++/87520 PR libstdc++/88782 * config/abi/pre/gnu.ver (GLIBCXX_3.4.26): Export new symbol. * include/bits/shared_ptr.h (shared_ptr(_Sp_make_shared_tag, const Alloc&, Args&&...)) (allocate_shared): Change to use new tag type. * include/bits/shared_ptr_base.h (_Sp_make_shared_tag::_S_eq): Declare new member function. (_Sp_alloc_shared_tag): Define new type. (_Sp_counted_ptr_inplace): Declare __shared_count<_Lp> as a friend. (_Sp_counted_ptr_inplace::_M_get_deleter) [!__cpp_rtti]: Use _Sp_make_shared_tag::_S_eq to check type_info. (__shared_count(Ptr, Deleter),__shared_count(Ptr, Deleter, Alloc)): Constrain to prevent being called with _Sp_alloc_shared_tag. (__shared_count(_Sp_make_shared_tag, const _Alloc&, Args&&...)): Replace constructor with ... (__shared_count(Tp*&, _Sp_alloc_shared_tag<_Alloc>, Args&&...)): Use reference parameter so address of the new object can be returned to the caller. Obtain the allocator from the tag type. (__shared_ptr(_Sp_make_shared_tag, const Alloc&, Args&&...)): Replace constructor with ... (__shared_ptr(_Sp_alloc_shared_tag<Alloc>, Args&&...)): Pass _M_ptr to the __shared_count constructor. (__allocate_shared): Change to use new tag type. * src/c++11/shared_ptr.cc (_Sp_make_shared_tag::_S_eq): Define. From-SVN: r268086
This commit is contained in:
Jonathan Wakely
Jonathan Wakely
parent
dea93fc60d
commit
fb54aa5915
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@ -1,3 +1,32 @@
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2019-01-18 Jonathan Wakely <jwakely@redhat.com>
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PR libstdc++/87514
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PR libstdc++/87520
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PR libstdc++/88782
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* config/abi/pre/gnu.ver (GLIBCXX_3.4.26): Export new symbol.
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* include/bits/shared_ptr.h
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(shared_ptr(_Sp_make_shared_tag, const Alloc&, Args&&...))
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(allocate_shared): Change to use new tag type.
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* include/bits/shared_ptr_base.h (_Sp_make_shared_tag::_S_eq):
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Declare new member function.
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(_Sp_alloc_shared_tag): Define new type.
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(_Sp_counted_ptr_inplace): Declare __shared_count<_Lp> as a friend.
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(_Sp_counted_ptr_inplace::_M_get_deleter) [!__cpp_rtti]: Use
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_Sp_make_shared_tag::_S_eq to check type_info.
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(__shared_count(Ptr, Deleter),__shared_count(Ptr, Deleter, Alloc)):
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Constrain to prevent being called with _Sp_alloc_shared_tag.
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(__shared_count(_Sp_make_shared_tag, const _Alloc&, Args&&...)):
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Replace constructor with ...
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(__shared_count(Tp*&, _Sp_alloc_shared_tag<_Alloc>, Args&&...)): Use
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reference parameter so address of the new object can be returned to
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the caller. Obtain the allocator from the tag type.
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(__shared_ptr(_Sp_make_shared_tag, const Alloc&, Args&&...)): Replace
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constructor with ...
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(__shared_ptr(_Sp_alloc_shared_tag<Alloc>, Args&&...)): Pass _M_ptr
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to the __shared_count constructor.
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(__allocate_shared): Change to use new tag type.
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* src/c++11/shared_ptr.cc (_Sp_make_shared_tag::_S_eq): Define.
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2019-01-17 Jonathan Wakely <jwakely@redhat.com>
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* src/c++17/fs_ops.cc
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@ -2235,6 +2235,9 @@ GLIBCXX_3.4.26 {
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_ZNSolsEDn;
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_ZNSt13basic_ostreamIwSt11char_traitsIwEElsEDn;
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# _Sp_make_shared_tag::_S_eq
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_ZNSt19_Sp_make_shared_tag5_S_eqERKSt9type_info;
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} GLIBCXX_3.4.25;
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# Symbols in the support library (libsupc++) have their own tag.
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@ -355,9 +355,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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private:
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// This constructor is non-standard, it is used by allocate_shared.
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template<typename _Alloc, typename... _Args>
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shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
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_Args&&... __args)
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: __shared_ptr<_Tp>(__tag, __a, std::forward<_Args>(__args)...)
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shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
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: __shared_ptr<_Tp>(__tag, std::forward<_Args>(__args)...)
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{ }
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template<typename _Yp, typename _Alloc, typename... _Args>
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@ -699,7 +698,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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inline shared_ptr<_Tp>
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allocate_shared(const _Alloc& __a, _Args&&... __args)
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{
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return shared_ptr<_Tp>(_Sp_make_shared_tag(), __a,
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return shared_ptr<_Tp>(_Sp_alloc_shared_tag<_Alloc>{__a},
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std::forward<_Args>(__args)...);
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}
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@ -501,8 +501,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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struct _Sp_make_shared_tag
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{
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private:
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template<typename _Tp, _Lock_policy _Lp>
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friend class __shared_ptr;
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template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
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friend class _Sp_counted_ptr_inplace;
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@ -512,8 +510,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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alignas(type_info) static constexpr char __tag[sizeof(type_info)] = { };
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return reinterpret_cast<const type_info&>(__tag);
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}
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static bool _S_eq(const type_info&) noexcept;
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};
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template<typename _Alloc>
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struct _Sp_alloc_shared_tag
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{
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const _Alloc& _M_a;
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};
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template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
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class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp>
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{
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@ -560,24 +566,31 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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this->~_Sp_counted_ptr_inplace();
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}
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// Sneaky trick so __shared_ptr can get the managed pointer.
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private:
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friend class __shared_count<_Lp>; // To be able to call _M_ptr().
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// No longer used, but code compiled against old libstdc++ headers
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// might still call it from __shared_ptr ctor to get the pointer out.
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virtual void*
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_M_get_deleter(const std::type_info& __ti) noexcept override
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{
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auto __ptr = const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
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// Check for the fake type_info first, so we don't try to access it
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// as a real type_info object.
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if (&__ti == &_Sp_make_shared_tag::_S_ti())
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return const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
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// as a real type_info object. Otherwise, check if it's the real
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// type_info for this class. With RTTI enabled we can check directly,
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// or call a library function to do it.
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if (&__ti == &_Sp_make_shared_tag::_S_ti()
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||
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#if __cpp_rtti
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// Callers compiled with old libstdc++ headers and RTTI enabled
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// might pass this instead:
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else if (__ti == typeid(_Sp_make_shared_tag))
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return const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
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__ti == typeid(_Sp_make_shared_tag)
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#else
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_Sp_make_shared_tag::_S_eq(__ti)
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#endif
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)
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return __ptr;
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return nullptr;
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}
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private:
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_Tp* _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); }
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_Impl _M_impl;
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@ -593,6 +606,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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template<_Lock_policy _Lp>
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class __shared_count
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{
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template<typename _Tp>
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struct __not_alloc_shared_tag { using type = void; };
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template<typename _Tp>
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struct __not_alloc_shared_tag<_Sp_alloc_shared_tag<_Tp>> { };
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public:
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constexpr __shared_count() noexcept : _M_pi(0)
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{ }
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@ -622,12 +641,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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: __shared_count(__p, __sp_array_delete{}, allocator<void>())
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{ }
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template<typename _Ptr, typename _Deleter>
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template<typename _Ptr, typename _Deleter,
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typename = typename __not_alloc_shared_tag<_Deleter>::type>
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__shared_count(_Ptr __p, _Deleter __d)
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: __shared_count(__p, std::move(__d), allocator<void>())
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{ }
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template<typename _Ptr, typename _Deleter, typename _Alloc>
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template<typename _Ptr, typename _Deleter, typename _Alloc,
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typename = typename __not_alloc_shared_tag<_Deleter>::type>
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__shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
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{
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typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
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@ -648,17 +669,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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}
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template<typename _Tp, typename _Alloc, typename... _Args>
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__shared_count(_Sp_make_shared_tag, _Tp*, const _Alloc& __a,
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__shared_count(_Tp*& __p, _Sp_alloc_shared_tag<_Alloc> __a,
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_Args&&... __args)
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: _M_pi(0)
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{
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typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type;
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typename _Sp_cp_type::__allocator_type __a2(__a);
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typename _Sp_cp_type::__allocator_type __a2(__a._M_a);
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auto __guard = std::__allocate_guarded(__a2);
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_Sp_cp_type* __mem = __guard.get();
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::new (__mem) _Sp_cp_type(__a, std::forward<_Args>(__args)...);
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_M_pi = __mem;
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auto __pi = ::new (__mem)
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_Sp_cp_type(__a._M_a, std::forward<_Args>(__args)...);
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__guard = nullptr;
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_M_pi = __pi;
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__p = __pi->_M_ptr();
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}
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#if _GLIBCXX_USE_DEPRECATED
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@ -1318,17 +1340,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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protected:
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// This constructor is non-standard, it is used by allocate_shared.
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template<typename _Alloc, typename... _Args>
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__shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
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_Args&&... __args)
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: _M_ptr(), _M_refcount(__tag, (_Tp*)0, __a,
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std::forward<_Args>(__args)...)
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{
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// _M_ptr needs to point to the newly constructed object.
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// This relies on _Sp_counted_ptr_inplace::_M_get_deleter.
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void* __p = _M_refcount._M_get_deleter(_Sp_make_shared_tag::_S_ti());
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_M_ptr = static_cast<_Tp*>(__p);
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_M_enable_shared_from_this_with(_M_ptr);
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}
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__shared_ptr(_Sp_alloc_shared_tag<_Alloc> __tag, _Args&&... __args)
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: _M_ptr(), _M_refcount(_M_ptr, __tag, std::forward<_Args>(__args)...)
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{ _M_enable_shared_from_this_with(_M_ptr); }
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template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
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typename... _Args>
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@ -1808,7 +1822,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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inline __shared_ptr<_Tp, _Lp>
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__allocate_shared(const _Alloc& __a, _Args&&... __args)
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{
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return __shared_ptr<_Tp, _Lp>(_Sp_make_shared_tag(), __a,
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return __shared_ptr<_Tp, _Lp>(_Sp_alloc_shared_tag<_Alloc>{__a},
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std::forward<_Args>(__args)...);
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}
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@ -94,5 +94,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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}
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#endif
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bool
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_Sp_make_shared_tag::_S_eq(const type_info& ti) noexcept
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{
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#if __cpp_rtti
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return ti == typeid(_Sp_make_shared_tag);
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#else
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// If libstdc++ itself is built with -fno-rtti then just assume that
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// make_shared and allocate_shared will never be used with -frtti.
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return false;
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#endif
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}
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace
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