// shared_ptr and weak_ptr implementation details -*- C++ -*-
-// Copyright (C) 2007-2013 Free Software Foundation, Inc.
+// Copyright (C) 2007-2014 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
#ifndef _SHARED_PTR_BASE_H
#define _SHARED_PTR_BASE_H 1
+#include <bits/allocated_ptr.h>
+#include <ext/aligned_buffer.h>
+
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
{ delete this; }
virtual void*
- _M_get_deleter(const std::type_info&) = 0;
+ _M_get_deleter(const std::type_info&) noexcept = 0;
void
_M_add_ref_copy()
void
_M_add_ref_lock();
-
+
+ bool
+ _M_add_ref_lock_nothrow();
+
void
_M_release() noexcept
{
_Sp_counted_base<_S_single>::
_M_add_ref_lock()
{
- if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)
- {
- _M_use_count = 0;
- __throw_bad_weak_ptr();
- }
+ if (_M_use_count == 0)
+ __throw_bad_weak_ptr();
+ ++_M_use_count;
}
template<>
_M_add_ref_lock()
{
// Perform lock-free add-if-not-zero operation.
- _Atomic_word __count = _M_use_count;
+ _Atomic_word __count = _M_get_use_count();
do
{
if (__count == 0)
__ATOMIC_RELAXED));
}
+ template<>
+ inline bool
+ _Sp_counted_base<_S_single>::
+ _M_add_ref_lock_nothrow()
+ {
+ if (_M_use_count == 0)
+ return false;
+ ++_M_use_count;
+ return true;
+ }
+
+ template<>
+ inline bool
+ _Sp_counted_base<_S_mutex>::
+ _M_add_ref_lock_nothrow()
+ {
+ __gnu_cxx::__scoped_lock sentry(*this);
+ if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)
+ {
+ _M_use_count = 0;
+ return false;
+ }
+ return true;
+ }
+
+ template<>
+ inline bool
+ _Sp_counted_base<_S_atomic>::
+ _M_add_ref_lock_nothrow()
+ {
+ // Perform lock-free add-if-not-zero operation.
+ _Atomic_word __count = _M_get_use_count();
+ do
+ {
+ if (__count == 0)
+ return false;
+ // Replace the current counter value with the old value + 1, as
+ // long as it's not changed meanwhile.
+ }
+ while (!__atomic_compare_exchange_n(&_M_use_count, &__count, __count + 1,
+ true, __ATOMIC_ACQ_REL,
+ __ATOMIC_RELAXED));
+ return true;
+ }
+
+ template<>
+ inline void
+ _Sp_counted_base<_S_single>::_M_add_ref_copy()
+ { ++_M_use_count; }
+
+ template<>
+ inline void
+ _Sp_counted_base<_S_single>::_M_release() noexcept
+ {
+ if (--_M_use_count == 0)
+ {
+ _M_dispose();
+ if (--_M_weak_count == 0)
+ _M_destroy();
+ }
+ }
+
+ template<>
+ inline void
+ _Sp_counted_base<_S_single>::_M_weak_add_ref() noexcept
+ { ++_M_weak_count; }
+
+ template<>
+ inline void
+ _Sp_counted_base<_S_single>::_M_weak_release() noexcept
+ {
+ if (--_M_weak_count == 0)
+ _M_destroy();
+ }
+
+ template<>
+ inline long
+ _Sp_counted_base<_S_single>::_M_get_use_count() const noexcept
+ { return _M_use_count; }
+
// Forward declarations.
template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
{
public:
explicit
- _Sp_counted_ptr(_Ptr __p)
+ _Sp_counted_ptr(_Ptr __p) noexcept
: _M_ptr(__p) { }
virtual void
{ delete this; }
virtual void*
- _M_get_deleter(const std::type_info&)
- { return 0; }
+ _M_get_deleter(const std::type_info&) noexcept
+ { return nullptr; }
_Sp_counted_ptr(const _Sp_counted_ptr&) = delete;
_Sp_counted_ptr& operator=(const _Sp_counted_ptr&) = delete;
- protected:
- _Ptr _M_ptr; // copy constructor must not throw
+ private:
+ _Ptr _M_ptr;
};
template<>
inline void
_Sp_counted_ptr<nullptr_t, _S_atomic>::_M_dispose() noexcept { }
+ template<int _Nm, typename _Tp,
+ bool __use_ebo = !__is_final(_Tp) && __is_empty(_Tp)>
+ struct _Sp_ebo_helper;
+
+ /// Specialization using EBO.
+ template<int _Nm, typename _Tp>
+ struct _Sp_ebo_helper<_Nm, _Tp, true> : private _Tp
+ {
+ explicit _Sp_ebo_helper(const _Tp& __tp) : _Tp(__tp) { }
+
+ static _Tp&
+ _S_get(_Sp_ebo_helper& __eboh) { return static_cast<_Tp&>(__eboh); }
+ };
+
+ /// Specialization not using EBO.
+ template<int _Nm, typename _Tp>
+ struct _Sp_ebo_helper<_Nm, _Tp, false>
+ {
+ explicit _Sp_ebo_helper(const _Tp& __tp) : _M_tp(__tp) { }
+
+ static _Tp&
+ _S_get(_Sp_ebo_helper& __eboh)
+ { return __eboh._M_tp; }
+
+ private:
+ _Tp _M_tp;
+ };
+
// Support for custom deleter and/or allocator
template<typename _Ptr, typename _Deleter, typename _Alloc, _Lock_policy _Lp>
class _Sp_counted_deleter final : public _Sp_counted_base<_Lp>
{
- // Helper class that stores the Deleter and also acts as an allocator.
- // Used to dispose of the owned pointer and the internal refcount
- // Requires that copies of _Alloc can free each other's memory.
- struct _My_Deleter
- : public _Alloc // copy constructor must not throw
+ class _Impl : _Sp_ebo_helper<0, _Deleter>, _Sp_ebo_helper<1, _Alloc>
{
- _Deleter _M_del; // copy constructor must not throw
- _My_Deleter(_Deleter __d, const _Alloc& __a)
- : _Alloc(__a), _M_del(__d) { }
+ typedef _Sp_ebo_helper<0, _Deleter> _Del_base;
+ typedef _Sp_ebo_helper<1, _Alloc> _Alloc_base;
+
+ public:
+ _Impl(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
+ : _M_ptr(__p), _Del_base(__d), _Alloc_base(__a)
+ { }
+
+ _Deleter& _M_del() noexcept { return _Del_base::_S_get(*this); }
+ _Alloc& _M_alloc() noexcept { return _Alloc_base::_S_get(*this); }
+
+ _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)
- : _M_ptr(__p), _M_del(__d, _Alloc()) { }
+ _Sp_counted_deleter(_Ptr __p, _Deleter __d) noexcept
+ : _M_impl(__p, __d, _Alloc()) { }
// __d(__p) must not throw.
- _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a)
- : _M_ptr(__p), _M_del(__d, __a) { }
+ _Sp_counted_deleter(_Ptr __p, _Deleter __d, const _Alloc& __a) noexcept
+ : _M_impl(__p, __d, __a) { }
~_Sp_counted_deleter() noexcept { }
virtual void
_M_dispose() noexcept
- { _M_del._M_del(_M_ptr); }
+ { _M_impl._M_del()(_M_impl._M_ptr); }
virtual void
_M_destroy() noexcept
{
- typedef typename allocator_traits<_Alloc>::template
- rebind_traits<_Sp_counted_deleter> _Alloc_traits;
- typename _Alloc_traits::allocator_type __a(_M_del);
- _Alloc_traits::destroy(__a, this);
- _Alloc_traits::deallocate(__a, this, 1);
+ __allocator_type __a(_M_impl._M_alloc());
+ __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
+ this->~_Sp_counted_deleter();
}
virtual void*
- _M_get_deleter(const std::type_info& __ti)
+ _M_get_deleter(const std::type_info& __ti) noexcept
{
#ifdef __GXX_RTTI
- return __ti == typeid(_Deleter) ? &_M_del._M_del : 0;
+ return __ti == typeid(_Deleter) ? &_M_impl._M_del() : nullptr;
#else
- return 0;
+ return nullptr;
#endif
}
- protected:
- _Ptr _M_ptr; // copy constructor must not throw
- _My_Deleter _M_del; // copy constructor must not throw
+ private:
+ _Impl _M_impl;
};
// helpers for make_shared / allocate_shared
template<typename _Tp, typename _Alloc, _Lock_policy _Lp>
class _Sp_counted_ptr_inplace final : public _Sp_counted_base<_Lp>
{
- // Helper class that stores the pointer and also acts as an allocator.
- // Used to dispose of the owned pointer and the internal refcount
- // Requires that copies of _Alloc can free each other's memory.
- struct _Impl
- : public _Alloc // copy constructor must not throw
+ class _Impl : _Sp_ebo_helper<0, _Alloc>
{
- _Impl(_Alloc __a) : _Alloc(__a), _M_ptr() { }
- _Tp* _M_ptr;
+ typedef _Sp_ebo_helper<0, _Alloc> _A_base;
+
+ public:
+ explicit _Impl(_Alloc __a) noexcept : _A_base(__a) { }
+
+ _Alloc& _M_alloc() noexcept { return _A_base::_S_get(*this); }
+
+ __gnu_cxx::__aligned_buffer<_Tp> _M_storage;
};
public:
+ using __allocator_type = __alloc_rebind<_Alloc, _Sp_counted_ptr_inplace>;
+
template<typename... _Args>
_Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
- : _M_impl(__a), _M_storage()
+ : _M_impl(__a)
{
- _M_impl._M_ptr = static_cast<_Tp*>(static_cast<void*>(&_M_storage));
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 2070. allocate_shared should use allocator_traits<A>::construct
- allocator_traits<_Alloc>::construct(__a, _M_impl._M_ptr,
+ allocator_traits<_Alloc>::construct(__a, _M_ptr(),
std::forward<_Args>(__args)...); // might throw
}
virtual void
_M_dispose() noexcept
- { allocator_traits<_Alloc>::destroy(_M_impl, _M_impl._M_ptr); }
+ {
+ allocator_traits<_Alloc>::destroy(_M_impl._M_alloc(), _M_ptr());
+ }
// Override because the allocator needs to know the dynamic type
virtual void
_M_destroy() noexcept
{
- typedef typename allocator_traits<_Alloc>::template
- rebind_traits<_Sp_counted_ptr_inplace> _Alloc_traits;
- typename _Alloc_traits::allocator_type __a(_M_impl);
- _Alloc_traits::destroy(__a, this);
- _Alloc_traits::deallocate(__a, this, 1);
+ __allocator_type __a(_M_impl._M_alloc());
+ __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
+ this->~_Sp_counted_ptr_inplace();
}
// Sneaky trick so __shared_ptr can get the managed pointer
_M_get_deleter(const std::type_info& __ti) noexcept
{
#ifdef __GXX_RTTI
- return __ti == typeid(_Sp_make_shared_tag)
- ? static_cast<void*>(&_M_storage)
- : 0;
-#else
- return 0;
+ if (__ti == typeid(_Sp_make_shared_tag))
+ return const_cast<typename remove_cv<_Tp>::type*>(_M_ptr());
#endif
+ return nullptr;
}
private:
+ _Tp* _M_ptr() noexcept { return _M_impl._M_storage._M_ptr(); }
+
_Impl _M_impl;
- typename aligned_storage<sizeof(_Tp), alignment_of<_Tp>::value>::type
- _M_storage;
};
+
template<_Lock_policy _Lp>
class __shared_count
{
}
template<typename _Ptr, typename _Deleter>
- __shared_count(_Ptr __p, _Deleter __d) : _M_pi(0)
- {
- // The allocator's value_type doesn't matter, will rebind it anyway.
- typedef std::allocator<int> _Alloc;
- typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
- typedef typename allocator_traits<_Alloc>::template
- rebind_traits<_Sp_cd_type> _Alloc_traits;
- typename _Alloc_traits::allocator_type __a;
- _Sp_cd_type* __mem = 0;
- __try
- {
- __mem = _Alloc_traits::allocate(__a, 1);
- _Alloc_traits::construct(__a, __mem, __p, std::move(__d));
- _M_pi = __mem;
- }
- __catch(...)
- {
- __d(__p); // Call _Deleter on __p.
- if (__mem)
- _Alloc_traits::deallocate(__a, __mem, 1);
- __throw_exception_again;
- }
- }
+ __shared_count(_Ptr __p, _Deleter __d)
+ : __shared_count(__p, std::move(__d), allocator<void>())
+ { }
template<typename _Ptr, typename _Deleter, typename _Alloc>
__shared_count(_Ptr __p, _Deleter __d, _Alloc __a) : _M_pi(0)
{
typedef _Sp_counted_deleter<_Ptr, _Deleter, _Alloc, _Lp> _Sp_cd_type;
- typedef typename allocator_traits<_Alloc>::template
- rebind_traits<_Sp_cd_type> _Alloc_traits;
- typename _Alloc_traits::allocator_type __a2(__a);
- _Sp_cd_type* __mem = 0;
__try
{
- __mem = _Alloc_traits::allocate(__a2, 1);
- _Alloc_traits::construct(__a2, __mem,
- __p, std::move(__d), std::move(__a));
+ typename _Sp_cd_type::__allocator_type __a2(__a);
+ auto __guard = std::__allocate_guarded(__a2);
+ _Sp_cd_type* __mem = __guard.get();
+ ::new (__mem) _Sp_cd_type(__p, std::move(__d), std::move(__a));
_M_pi = __mem;
+ __guard = nullptr;
}
__catch(...)
{
__d(__p); // Call _Deleter on __p.
- if (__mem)
- _Alloc_traits::deallocate(__a2, __mem, 1);
__throw_exception_again;
}
}
: _M_pi(0)
{
typedef _Sp_counted_ptr_inplace<_Tp, _Alloc, _Lp> _Sp_cp_type;
- typedef typename allocator_traits<_Alloc>::template
- rebind_traits<_Sp_cp_type> _Alloc_traits;
- typename _Alloc_traits::allocator_type __a2(__a);
- _Sp_cp_type* __mem = _Alloc_traits::allocate(__a2, 1);
- __try
- {
- _Alloc_traits::construct(__a2, __mem, std::move(__a),
- std::forward<_Args>(__args)...);
- _M_pi = __mem;
- }
- __catch(...)
- {
- _Alloc_traits::deallocate(__a2, __mem, 1);
- __throw_exception_again;
- }
+ typename _Sp_cp_type::__allocator_type __a2(__a);
+ auto __guard = std::__allocate_guarded(__a2);
+ _Sp_cp_type* __mem = __guard.get();
+ ::new (__mem) _Sp_cp_type(std::move(__a),
+ std::forward<_Args>(__args)...);
+ _M_pi = __mem;
+ __guard = nullptr;
}
#if _GLIBCXX_USE_DEPRECATED
// Special case for unique_ptr<_Tp,_Del> to provide the strong guarantee.
template<typename _Tp, typename _Del>
explicit
- __shared_count(std::unique_ptr<_Tp, _Del>&& __r)
- : _M_pi(_S_create_from_up(std::move(__r)))
- { __r.release(); }
+ __shared_count(std::unique_ptr<_Tp, _Del>&& __r) : _M_pi(0)
+ {
+ using _Ptr = typename unique_ptr<_Tp, _Del>::pointer;
+ using _Del2 = typename conditional<is_reference<_Del>::value,
+ reference_wrapper<typename remove_reference<_Del>::type>,
+ _Del>::type;
+ using _Sp_cd_type
+ = _Sp_counted_deleter<_Ptr, _Del2, allocator<void>, _Lp>;
+ using _Alloc = allocator<_Sp_cd_type>;
+ using _Alloc_traits = allocator_traits<_Alloc>;
+ _Alloc __a;
+ _Sp_cd_type* __mem = _Alloc_traits::allocate(__a, 1);
+ _Alloc_traits::construct(__a, __mem, __r.release(),
+ __r.get_deleter()); // non-throwing
+ _M_pi = __mem;
+ }
// Throw bad_weak_ptr when __r._M_get_use_count() == 0.
explicit __shared_count(const __weak_count<_Lp>& __r);
+ // Does not throw if __r._M_get_use_count() == 0, caller must check.
+ explicit __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t);
+
~__shared_count() noexcept
{
- if (_M_pi != 0)
+ if (_M_pi != nullptr)
_M_pi->_M_release();
}
void*
_M_get_deleter(const std::type_info& __ti) const noexcept
- { return _M_pi ? _M_pi->_M_get_deleter(__ti) : 0; }
+ { return _M_pi ? _M_pi->_M_get_deleter(__ti) : nullptr; }
bool
_M_less(const __shared_count& __rhs) const noexcept
private:
friend class __weak_count<_Lp>;
- template<typename _Tp, typename _Del>
- static _Sp_counted_base<_Lp>*
- _S_create_from_up(std::unique_ptr<_Tp, _Del>&& __r,
- typename std::enable_if<!std::is_reference<_Del>::value>::type* = 0)
- {
- typedef typename unique_ptr<_Tp, _Del>::pointer _Ptr;
- return new _Sp_counted_deleter<_Ptr, _Del, std::allocator<void>,
- _Lp>(__r.get(), __r.get_deleter());
- }
-
- template<typename _Tp, typename _Del>
- static _Sp_counted_base<_Lp>*
- _S_create_from_up(std::unique_ptr<_Tp, _Del>&& __r,
- typename std::enable_if<std::is_reference<_Del>::value>::type* = 0)
- {
- typedef typename unique_ptr<_Tp, _Del>::pointer _Ptr;
- typedef typename std::remove_reference<_Del>::type _Del1;
- typedef std::reference_wrapper<_Del1> _Del2;
- return new _Sp_counted_deleter<_Ptr, _Del2, std::allocator<void>,
- _Lp>(__r.get(), std::ref(__r.get_deleter()));
- }
-
_Sp_counted_base<_Lp>* _M_pi;
};
// Now that __weak_count is defined we can define this constructor:
template<_Lock_policy _Lp>
- inline __shared_count<_Lp>:: __shared_count(const __weak_count<_Lp>& __r)
+ inline
+ __shared_count<_Lp>::__shared_count(const __weak_count<_Lp>& __r)
: _M_pi(__r._M_pi)
{
- if (_M_pi != 0)
+ if (_M_pi != nullptr)
_M_pi->_M_add_ref_lock();
else
__throw_bad_weak_ptr();
}
+ // Now that __weak_count is defined we can define this constructor:
+ template<_Lock_policy _Lp>
+ inline
+ __shared_count<_Lp>::
+ __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t)
+ : _M_pi(__r._M_pi)
+ {
+ if (_M_pi != nullptr)
+ if (!_M_pi->_M_add_ref_lock_nothrow())
+ _M_pi = nullptr;
+ }
// Support for enable_shared_from_this.
: _M_ptr(__p), _M_refcount(__p)
{
__glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
+ static_assert( !is_void<_Tp1>::value, "incomplete type" );
static_assert( sizeof(_Tp1) > 0, "incomplete type" );
__enable_shared_from_this_helper(_M_refcount, __p, __p);
}
: _M_ptr(__r.get()), _M_refcount()
{
__glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
- auto __tmp = std::__addressof(*__r.get());
+ auto __raw = _S_raw_ptr(__r.get());
_M_refcount = __shared_count<_Lp>(std::move(__r));
- __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp);
+ __enable_shared_from_this_helper(_M_refcount, __raw, __raw);
}
#if _GLIBCXX_USE_DEPRECATED
__shared_ptr(std::auto_ptr<_Tp1>&& __r);
#endif
- /* TODO: use delegating constructor */
- constexpr __shared_ptr(nullptr_t) noexcept
- : _M_ptr(0), _M_refcount()
- { }
+ constexpr __shared_ptr(nullptr_t) noexcept : __shared_ptr() { }
template<typename _Tp1>
__shared_ptr&
{
void operator()(_Tp* __ptr)
{
- typedef allocator_traits<_Alloc> _Alloc_traits;
- _Alloc_traits::destroy(_M_alloc, __ptr);
- _Alloc_traits::deallocate(_M_alloc, __ptr, 1);
+ __allocated_ptr<_Alloc> __guard{ _M_alloc, __ptr };
+ allocator_traits<_Alloc>::destroy(_M_alloc, __guard.get());
}
_Alloc _M_alloc;
};
__shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
_Args&&... __args)
: _M_ptr(), _M_refcount()
- {
- typedef typename _Alloc::template rebind<_Tp>::other _Alloc2;
- _Deleter<_Alloc2> __del = { _Alloc2(__a) };
- typedef allocator_traits<_Alloc2> __traits;
- _M_ptr = __traits::allocate(__del._M_alloc, 1);
- __try
- {
- // _GLIBCXX_RESOLVE_LIB_DEFECTS
- // 2070. allocate_shared should use allocator_traits<A>::construct
- __traits::construct(__del._M_alloc, _M_ptr,
- std::forward<_Args>(__args)...);
- }
- __catch(...)
- {
- __traits::deallocate(__del._M_alloc, _M_ptr, 1);
- __throw_exception_again;
- }
- __shared_count<_Lp> __count(_M_ptr, __del, __del._M_alloc);
- _M_refcount._M_swap(__count);
+ {
+ typedef typename allocator_traits<_Alloc>::template
+ rebind_traits<_Tp> __traits;
+ _Deleter<typename __traits::allocator_type> __del = { __a };
+ auto __guard = std::__allocate_guarded(__del._M_alloc);
+ _M_ptr = __guard.get();
+ // _GLIBCXX_RESOLVE_LIB_DEFECTS
+ // 2070. allocate_shared should use allocator_traits<A>::construct
+ __traits::construct(__del._M_alloc, _M_ptr,
+ std::forward<_Args>(__args)...);
+ __guard = nullptr;
+ __shared_count<_Lp> __count(_M_ptr, __del, __del._M_alloc);
+ _M_refcount._M_swap(__count);
__enable_shared_from_this_helper(_M_refcount, _M_ptr, _M_ptr);
- }
+ }
#endif
template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
friend __shared_ptr<_Tp1, _Lp1>
__allocate_shared(const _Alloc& __a, _Args&&... __args);
+ // This constructor is used by __weak_ptr::lock() and
+ // shared_ptr::shared_ptr(const weak_ptr&, std::nothrow_t).
+ __shared_ptr(const __weak_ptr<_Tp, _Lp>& __r, std::nothrow_t)
+ : _M_refcount(__r._M_refcount, std::nothrow)
+ {
+ _M_ptr = _M_refcount._M_get_use_count() ? __r._M_ptr : nullptr;
+ }
+
+ friend class __weak_ptr<_Tp, _Lp>;
+
private:
void*
_M_get_deleter(const std::type_info& __ti) const noexcept
{ return _M_refcount._M_get_deleter(__ti); }
+ template<typename _Tp1>
+ static _Tp1*
+ _S_raw_ptr(_Tp1* __ptr)
+ { return __ptr; }
+
+ template<typename _Tp1>
+ static auto
+ _S_raw_ptr(_Tp1 __ptr) -> decltype(std::__addressof(*__ptr))
+ { return std::__addressof(*__ptr); }
+
template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
: public _Sp_less<__shared_ptr<_Tp, _Lp>>
{ };
- // 2.2.3.8 shared_ptr specialized algorithms.
+ // 20.7.2.2.8 shared_ptr specialized algorithms.
template<typename _Tp, _Lock_policy _Lp>
inline void
swap(__shared_ptr<_Tp, _Lp>& __a, __shared_ptr<_Tp, _Lp>& __b) noexcept
{ __a.swap(__b); }
- // 2.2.3.9 shared_ptr casts
+ // 20.7.2.2.9 shared_ptr casts
// The seemingly equivalent code:
// shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
__shared_ptr<_Tp, _Lp>
lock() const noexcept
- {
-#ifdef __GTHREADS
- // Optimization: avoid throw overhead.
- if (expired())
- return __shared_ptr<element_type, _Lp>();
-
- __try
- {
- return __shared_ptr<element_type, _Lp>(*this);
- }
- __catch(const bad_weak_ptr&)
- {
- // Q: How can we get here?
- // A: Another thread may have invalidated r after the
- // use_count test above.
- return __shared_ptr<element_type, _Lp>();
- }
-
-#else
- // Optimization: avoid try/catch overhead when single threaded.
- return expired() ? __shared_ptr<element_type, _Lp>()
- : __shared_ptr<element_type, _Lp>(*this);
-
-#endif
- } // XXX MT
+ { return __shared_ptr<element_type, _Lp>(*this, std::nothrow); }
long
use_count() const noexcept
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