Exceptions

Namespaces
	std::__exception_ptr

Classes
class	std::__exception_ptr::exception_ptr
	An opaque pointer to an arbitrary exception. More...
class	std::exception
	STL class.
class	std::bad_exception
	STL class.
class	std::bad_alloc
	STL class.
class	std::bad_cast
	STL class.
class	std::bad_typeid
	STL class.

Typedefs
typedef void(*	std::terminate_handler )()
	If you write a replacement terminate handler, it must be of this type. More...
typedef void(*	std::unexpected_handler )()
	If you write a replacement unexpected handler, it must be of this type. More...

Functions
exception_ptr	std::current_exception () _GLIBCXX_USE_NOEXCEPT
void	std::rethrow_exception (exception_ptr) __attribute__((__noreturn__))
	Throw the object pointed to by the exception_ptr. More...
template<typename _Ex >
exception_ptr	std::copy_exception (_Ex __ex) _GLIBCXX_USE_NOEXCEPT
	Obtain an exception_ptr pointing to a copy of the supplied object. More...
template<typename _Ex >
exception_ptr	std::make_exception_ptr (_Ex __ex) _GLIBCXX_USE_NOEXCEPT
	Obtain an exception_ptr pointing to a copy of the supplied object. More...
namespace std	_GLIBCXX_VISIBILITY (default)
terminate_handler	std::set_terminate (terminate_handler) _GLIBCXX_USE_NOEXCEPT
	Takes a new handler function as an argument, returns the old function. More...
void	std::terminate () _GLIBCXX_USE_NOEXCEPT __attribute__((__noreturn__))
unexpected_handler	std::set_unexpected (unexpected_handler) _GLIBCXX_USE_NOEXCEPT
	Takes a new handler function as an argument, returns the old function. More...
void	std::unexpected () __attribute__((__noreturn__))
bool	std::uncaught_exception () _GLIBCXX_USE_NOEXCEPT __attribute__((__pure__))
_GLIBCXX_BEGIN_NAMESPACE_VERSION void	__gnu_cxx::__verbose_terminate_handler ()
	A replacement for the standard terminate_handler which prints more information about the terminating exception (if any) on stderr. More...

Detailed Description

Classes and functions for reporting errors via exception classes.

Typedef Documentation

typedef void(* std::terminate_handler)()

If you write a replacement terminate handler, it must be of this type.

typedef void(* std::unexpected_handler)()

If you write a replacement unexpected handler, it must be of this type.

Function Documentation

_GLIBCXX_BEGIN_NAMESPACE_VERSION void __gnu_cxx::__verbose_terminate_handler

(

)

A replacement for the standard terminate_handler which prints more information about the terminating exception (if any) on stderr.

Call

std::set_terminate(__gnu_cxx::__verbose_terminate_handler)

to use. For more info, see http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt02ch06s02.html

In 3.4 and later, this is on by default.

namespace std _GLIBCXX_VISIBILITY

(

default

)

Exception possibly thrown by shared_ptr.

static_pointer_cast

const_pointer_cast

dynamic_pointer_cast

std::hash specialization for __shared_ptr.

Thown by exception safety machinery.

Base class for checking address and label information about allocations. Create a std::map between the allocated address (void*) and a datum for annotations, which are a pair of numbers corresponding to label and allocated size.

Base struct for condition policy.

Requires a public member function with the signature void throw_conditionally()

Base class for incremental control and throw.

Never enter the condition.

Always enter the condition.

Enter the nth condition.

Base class for random probability control and throw.

Group condition.

Never enter the condition.

Always enter the condition.

Class with exception generation control. Intended to be used as a value_type in templatized code.

Note: Destructor not allowed to throw.

Type throwing via limit condition.

Type throwing via random condition.

Allocator class with logging and exception generation control. Intended to be used as an allocator_type in templatized code.

Note: Deallocate not allowed to throw.

Allocator throwing via limit condition.

Allocator throwing via random condition.

Exception possibly thrown by shared_ptr.

{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

#if _GLIBCXX_USE_DEPRECATED
  template<typename> class auto_ptr;
#endif

  class bad_weak_ptr : public std::exception
  {
  public:
    virtual char const*
    what() const noexcept;

    virtual ~bad_weak_ptr() noexcept;    
  };

  // Substitute for bad_weak_ptr object in the case of -fno-exceptions.
  inline void
  __throw_bad_weak_ptr()
  { _GLIBCXX_THROW_OR_ABORT(bad_weak_ptr()); }

  using __gnu_cxx::_Lock_policy;
  using __gnu_cxx::__default_lock_policy;
  using __gnu_cxx::_S_single;
  using __gnu_cxx::_S_mutex;
  using __gnu_cxx::_S_atomic;

  // Empty helper class except when the template argument is _S_mutex.
  template<_Lock_policy _Lp>
    class _Mutex_base
    {
    protected:
      // The atomic policy uses fully-fenced builtins, single doesn't care.
      enum { _S_need_barriers = 0 };
    };

  template<>
    class _Mutex_base<_S_mutex>
    : public __gnu_cxx::__mutex
    {
    protected:
      // This policy is used when atomic builtins are not available.
      // The replacement atomic operations might not have the necessary
      // memory barriers.
      enum { _S_need_barriers = 1 };
    };

  template<_Lock_policy _Lp = __default_lock_policy>
    class _Sp_counted_base
    : public _Mutex_base<_Lp>
    {
    public:  
      _Sp_counted_base() noexcept
      : _M_use_count(1), _M_weak_count(1) { }
      
      virtual
      ~_Sp_counted_base() noexcept
      { }
  
      // Called when _M_use_count drops to zero, to release the resources
      // managed by *this.
      virtual void
      _M_dispose() noexcept = 0;
      
      // Called when _M_weak_count drops to zero.
      virtual void
      _M_destroy() noexcept
      { delete this; }
      
      virtual void*
      _M_get_deleter(const std::type_info&) = 0;

      void
      _M_add_ref_copy()
      { __gnu_cxx::__atomic_add_dispatch(&_M_use_count, 1); }
  
      void
      _M_add_ref_lock();
      
      void
      _M_release() noexcept
      {
        // Be race-detector-friendly.  For more info see bits/c++config.
        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);
    if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1)
      {
            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
        _M_dispose();
        // There must be a memory barrier between dispose() and destroy()
        // to ensure that the effects of dispose() are observed in the
        // thread that runs destroy().
        // See http://gcc.gnu.org/ml/libstdc++/2005-11/msg00136.html
        if (_Mutex_base<_Lp>::_S_need_barriers)
          {
            _GLIBCXX_READ_MEM_BARRIER;
            _GLIBCXX_WRITE_MEM_BARRIER;
          }

            // Be race-detector-friendly.  For more info see bits/c++config.
            _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
        if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count,
                               -1) == 1)
              {
                _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
            _M_destroy();
              }
      }
      }
  
      void
      _M_weak_add_ref() noexcept
      { __gnu_cxx::__atomic_add_dispatch(&_M_weak_count, 1); }

      void
      _M_weak_release() noexcept
      {
        // Be race-detector-friendly. For more info see bits/c++config.
        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
    if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count, -1) == 1)
      {
            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
        if (_Mutex_base<_Lp>::_S_need_barriers)
          {
            // See _M_release(),
            // destroy() must observe results of dispose()
            _GLIBCXX_READ_MEM_BARRIER;
            _GLIBCXX_WRITE_MEM_BARRIER;
          }
        _M_destroy();
      }
      }
  
      long
      _M_get_use_count() const noexcept
      {
        // No memory barrier is used here so there is no synchronization
        // with other threads.
        return __atomic_load_n(&_M_use_count, __ATOMIC_RELAXED);
      }

    private:  
      _Sp_counted_base(_Sp_counted_base const&) = delete;
      _Sp_counted_base& operator=(_Sp_counted_base const&) = delete;

      _Atomic_word  _M_use_count;     // #shared
      _Atomic_word  _M_weak_count;    // #weak + (#shared != 0)
    };

  template<>
    inline void
    _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();
    }
    }

  template<>
    inline void
    _Sp_counted_base<_S_mutex>::
    _M_add_ref_lock()
    {
      __gnu_cxx::__scoped_lock sentry(*this);
      if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, 1) == 0)
    {
      _M_use_count = 0;
      __throw_bad_weak_ptr();
    }
    }

  template<> 
    inline void
    _Sp_counted_base<_S_atomic>::
    _M_add_ref_lock()
    {
      // Perform lock-free add-if-not-zero operation.
      _Atomic_word __count = _M_get_use_count();
      do
    {
      if (__count == 0)
        __throw_bad_weak_ptr();
      // 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));
    }


  // Forward declarations.
  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
    class __shared_ptr;

  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
    class __weak_ptr;

  template<typename _Tp, _Lock_policy _Lp = __default_lock_policy>
    class __enable_shared_from_this;

  template<typename _Tp>
    class shared_ptr;

  template<typename _Tp>
    class weak_ptr;

  template<typename _Tp>
    struct owner_less;

  template<typename _Tp>
    class enable_shared_from_this;

  template<_Lock_policy _Lp = __default_lock_policy>
    class __weak_count;

  template<_Lock_policy _Lp = __default_lock_policy>
    class __shared_count;


  // Counted ptr with no deleter or allocator support
  template<typename _Ptr, _Lock_policy _Lp>
    class _Sp_counted_ptr final : public _Sp_counted_base<_Lp>
    {
    public:
      explicit
      _Sp_counted_ptr(_Ptr __p)
      : _M_ptr(__p) { }

      virtual void
      _M_dispose() noexcept
      { delete _M_ptr; }

      virtual void
      _M_destroy() noexcept
      { delete this; }

      virtual void*
      _M_get_deleter(const std::type_info&)
      { return 0; }

      _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
    };

  template<>
    inline void
    _Sp_counted_ptr<nullptr_t, _S_single>::_M_dispose() noexcept { }

  template<>
    inline void
    _Sp_counted_ptr<nullptr_t, _S_mutex>::_M_dispose() noexcept { }

  template<>
    inline void
    _Sp_counted_ptr<nullptr_t, _S_atomic>::_M_dispose() noexcept { }

  // 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
      {
    _Deleter _M_del;        // copy constructor must not throw
    _My_Deleter(_Deleter __d, const _Alloc& __a)
    : _Alloc(__a), _M_del(__d) { }
      };

    public:
      // __d(__p) must not throw.
      _Sp_counted_deleter(_Ptr __p, _Deleter __d)
      : _M_ptr(__p), _M_del(__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() noexcept { }

      virtual void
      _M_dispose() noexcept
      { _M_del._M_del(_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);
      }

      virtual void*
      _M_get_deleter(const std::type_info& __ti)
      {
#ifdef __GXX_RTTI
        return __ti == typeid(_Deleter) ? &_M_del._M_del : 0;
#else
        return 0;
#endif
      }

    protected:
      _Ptr             _M_ptr;  // copy constructor must not throw
      _My_Deleter      _M_del;  // copy constructor must not throw
    };

  // helpers for make_shared / allocate_shared

  struct _Sp_make_shared_tag { };

  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
      {
    _Impl(_Alloc __a) : _Alloc(__a), _M_ptr() { }
    _Tp* _M_ptr;
      };

    public:
      template<typename... _Args>
    _Sp_counted_ptr_inplace(_Alloc __a, _Args&&... __args)
    : _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,
          std::forward<_Args>(__args)...); // might throw
    }

      ~_Sp_counted_ptr_inplace() noexcept { }

      virtual void
      _M_dispose() noexcept
      { allocator_traits<_Alloc>::destroy(_M_impl, _M_impl._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);
      }

      // Sneaky trick so __shared_ptr can get the managed pointer
      virtual void*
      _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;
#endif
      }

    private:
      _Impl _M_impl;
      typename aligned_storage<sizeof(_Tp), alignment_of<_Tp>::value>::type
    _M_storage;
    };

  template<_Lock_policy _Lp>
    class __shared_count
    {
    public:
      constexpr __shared_count() noexcept : _M_pi(0)
      { }

      template<typename _Ptr>
        explicit
    __shared_count(_Ptr __p) : _M_pi(0)
    {
      __try
        {
          _M_pi = new _Sp_counted_ptr<_Ptr, _Lp>(__p);
        }
      __catch(...)
        {
          delete __p;
          __throw_exception_again;
        }
    }

      template<typename _Ptr, typename _Deleter>
    __shared_count(_Ptr __p, _Deleter __d)
    : __shared_count(__p, std::move(__d), allocator<int>())
    { }

      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));
          _M_pi = __mem;
        }
      __catch(...)
        {
          __d(__p); // Call _Deleter on __p.
          if (__mem)
            _Alloc_traits::deallocate(__a2, __mem, 1);
          __throw_exception_again;
        }
    }

      template<typename _Tp, typename _Alloc, typename... _Args>
    __shared_count(_Sp_make_shared_tag, _Tp*, const _Alloc& __a,
               _Args&&... __args)
    : _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;
        }
    }

#if _GLIBCXX_USE_DEPRECATED
      // Special case for auto_ptr<_Tp> to provide the strong guarantee.
      template<typename _Tp>
        explicit
    __shared_count(std::auto_ptr<_Tp>&& __r);
#endif

      // 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(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);

      ~__shared_count() noexcept
      {
    if (_M_pi != nullptr)
      _M_pi->_M_release();
      }

      __shared_count(const __shared_count& __r) noexcept
      : _M_pi(__r._M_pi)
      {
    if (_M_pi != 0)
      _M_pi->_M_add_ref_copy();
      }

      __shared_count&
      operator=(const __shared_count& __r) noexcept
      {
    _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
    if (__tmp != _M_pi)
      {
        if (__tmp != 0)
          __tmp->_M_add_ref_copy();
        if (_M_pi != 0)
          _M_pi->_M_release();
        _M_pi = __tmp;
      }
    return *this;
      }

      void
      _M_swap(__shared_count& __r) noexcept
      {
    _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
    __r._M_pi = _M_pi;
    _M_pi = __tmp;
      }

      long
      _M_get_use_count() const noexcept
      { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }

      bool
      _M_unique() const noexcept
      { return this->_M_get_use_count() == 1; }

      void*
      _M_get_deleter(const std::type_info& __ti) const noexcept
      { return _M_pi ? _M_pi->_M_get_deleter(__ti) : 0; }

      bool
      _M_less(const __shared_count& __rhs) const noexcept
      { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }

      bool
      _M_less(const __weak_count<_Lp>& __rhs) const noexcept
      { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }

      // Friend function injected into enclosing namespace and found by ADL
      friend inline bool
      operator==(const __shared_count& __a, const __shared_count& __b) noexcept
      { return __a._M_pi == __b._M_pi; }

    private:
      friend class __weak_count<_Lp>;

      _Sp_counted_base<_Lp>*  _M_pi;
    };


  template<_Lock_policy _Lp>
    class __weak_count
    {
    public:
      constexpr __weak_count() noexcept : _M_pi(0)
      { }

      __weak_count(const __shared_count<_Lp>& __r) noexcept
      : _M_pi(__r._M_pi)
      {
    if (_M_pi != 0)
      _M_pi->_M_weak_add_ref();
      }

      __weak_count(const __weak_count<_Lp>& __r) noexcept
      : _M_pi(__r._M_pi)
      {
    if (_M_pi != 0)
      _M_pi->_M_weak_add_ref();
      }

      ~__weak_count() noexcept
      {
    if (_M_pi != 0)
      _M_pi->_M_weak_release();
      }

      __weak_count<_Lp>&
      operator=(const __shared_count<_Lp>& __r) noexcept
      {
    _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
    if (__tmp != 0)
      __tmp->_M_weak_add_ref();
    if (_M_pi != 0)
      _M_pi->_M_weak_release();
    _M_pi = __tmp;
    return *this;
      }

      __weak_count<_Lp>&
      operator=(const __weak_count<_Lp>& __r) noexcept
      {
    _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
    if (__tmp != 0)
      __tmp->_M_weak_add_ref();
    if (_M_pi != 0)
      _M_pi->_M_weak_release();
    _M_pi = __tmp;
    return *this;
      }

      void
      _M_swap(__weak_count<_Lp>& __r) noexcept
      {
    _Sp_counted_base<_Lp>* __tmp = __r._M_pi;
    __r._M_pi = _M_pi;
    _M_pi = __tmp;
      }

      long
      _M_get_use_count() const noexcept
      { return _M_pi != 0 ? _M_pi->_M_get_use_count() : 0; }

      bool
      _M_less(const __weak_count& __rhs) const noexcept
      { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }

      bool
      _M_less(const __shared_count<_Lp>& __rhs) const noexcept
      { return std::less<_Sp_counted_base<_Lp>*>()(this->_M_pi, __rhs._M_pi); }

      // Friend function injected into enclosing namespace and found by ADL
      friend inline bool
      operator==(const __weak_count& __a, const __weak_count& __b) noexcept
      { return __a._M_pi == __b._M_pi; }

    private:
      friend class __shared_count<_Lp>;

      _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)
    : _M_pi(__r._M_pi)
    {
      if (_M_pi != 0)
    _M_pi->_M_add_ref_lock();
      else
    __throw_bad_weak_ptr();
    }


  // Support for enable_shared_from_this.

  // Friend of __enable_shared_from_this.
  template<_Lock_policy _Lp, typename _Tp1, typename _Tp2>
    void
    __enable_shared_from_this_helper(const __shared_count<_Lp>&,
                     const __enable_shared_from_this<_Tp1,
                     _Lp>*, const _Tp2*) noexcept;

  // Friend of enable_shared_from_this.
  template<typename _Tp1, typename _Tp2>
    void
    __enable_shared_from_this_helper(const __shared_count<>&,
                     const enable_shared_from_this<_Tp1>*,
                     const _Tp2*) noexcept;

  template<_Lock_policy _Lp>
    inline void
    __enable_shared_from_this_helper(const __shared_count<_Lp>&, ...) noexcept
    { }


  template<typename _Tp, _Lock_policy _Lp>
    class __shared_ptr
    {
    public:
      typedef _Tp   element_type;

      constexpr __shared_ptr() noexcept
      : _M_ptr(0), _M_refcount()
      { }

      template<typename _Tp1>
    explicit __shared_ptr(_Tp1* __p)
        : _M_ptr(__p), _M_refcount(__p)
    {
      __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
      static_assert( sizeof(_Tp1) > 0, "incomplete type" );
      __enable_shared_from_this_helper(_M_refcount, __p, __p);
    }

      template<typename _Tp1, typename _Deleter>
    __shared_ptr(_Tp1* __p, _Deleter __d)
    : _M_ptr(__p), _M_refcount(__p, __d)
    {
      __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
      // TODO requires _Deleter CopyConstructible and __d(__p) well-formed
      __enable_shared_from_this_helper(_M_refcount, __p, __p);
    }

      template<typename _Tp1, typename _Deleter, typename _Alloc>
    __shared_ptr(_Tp1* __p, _Deleter __d, _Alloc __a)
    : _M_ptr(__p), _M_refcount(__p, __d, std::move(__a))
    {
      __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
      // TODO requires _Deleter CopyConstructible and __d(__p) well-formed
      __enable_shared_from_this_helper(_M_refcount, __p, __p);
    }

      template<typename _Deleter>
    __shared_ptr(nullptr_t __p, _Deleter __d)
    : _M_ptr(0), _M_refcount(__p, __d)
    { }

      template<typename _Deleter, typename _Alloc>
        __shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a)
    : _M_ptr(0), _M_refcount(__p, __d, std::move(__a))
    { }

      template<typename _Tp1>
    __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r, _Tp* __p) noexcept
    : _M_ptr(__p), _M_refcount(__r._M_refcount) // never throws
    { }

      __shared_ptr(const __shared_ptr&) noexcept = default;
      __shared_ptr& operator=(const __shared_ptr&) noexcept = default;
      ~__shared_ptr() = default;

      template<typename _Tp1, typename = typename
           std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
    __shared_ptr(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
    : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
    { }

      __shared_ptr(__shared_ptr&& __r) noexcept
      : _M_ptr(__r._M_ptr), _M_refcount()
      {
    _M_refcount._M_swap(__r._M_refcount);
    __r._M_ptr = 0;
      }

      template<typename _Tp1, typename = typename
           std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
    __shared_ptr(__shared_ptr<_Tp1, _Lp>&& __r) noexcept
    : _M_ptr(__r._M_ptr), _M_refcount()
    {
      _M_refcount._M_swap(__r._M_refcount);
      __r._M_ptr = 0;
    }

      template<typename _Tp1>
    explicit __shared_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
    : _M_refcount(__r._M_refcount) // may throw
    {
      __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)

      // It is now safe to copy __r._M_ptr, as
      // _M_refcount(__r._M_refcount) did not throw.
      _M_ptr = __r._M_ptr;
    }

      // If an exception is thrown this constructor has no effect.
      template<typename _Tp1, typename _Del>
    __shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r)
    : _M_ptr(__r.get()), _M_refcount()
    {
      __glibcxx_function_requires(_ConvertibleConcept<_Tp1*, _Tp*>)
      auto __tmp = __r.get();
      _M_refcount = __shared_count<_Lp>(std::move(__r));
      __enable_shared_from_this_helper(_M_refcount, __tmp, __tmp);
    }

#if _GLIBCXX_USE_DEPRECATED
      // Postcondition: use_count() == 1 and __r.get() == 0
      template<typename _Tp1>
    __shared_ptr(std::auto_ptr<_Tp1>&& __r);
#endif

      /* TODO: use delegating constructor */
      constexpr __shared_ptr(nullptr_t) noexcept
      : _M_ptr(0), _M_refcount()
      { }

      template<typename _Tp1>
    __shared_ptr&
    operator=(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
    {
      _M_ptr = __r._M_ptr;
      _M_refcount = __r._M_refcount; // __shared_count::op= doesn't throw
      return *this;
    }

#if _GLIBCXX_USE_DEPRECATED
      template<typename _Tp1>
    __shared_ptr&
    operator=(std::auto_ptr<_Tp1>&& __r)
    {
      __shared_ptr(std::move(__r)).swap(*this);
      return *this;
    }
#endif

      __shared_ptr&
      operator=(__shared_ptr&& __r) noexcept
      {
    __shared_ptr(std::move(__r)).swap(*this);
    return *this;
      }

      template<class _Tp1>
    __shared_ptr&
    operator=(__shared_ptr<_Tp1, _Lp>&& __r) noexcept
    {
      __shared_ptr(std::move(__r)).swap(*this);
      return *this;
    }

      template<typename _Tp1, typename _Del>
    __shared_ptr&
    operator=(std::unique_ptr<_Tp1, _Del>&& __r)
    {
      __shared_ptr(std::move(__r)).swap(*this);
      return *this;
    }

      void
      reset() noexcept
      { __shared_ptr().swap(*this); }

      template<typename _Tp1>
    void
    reset(_Tp1* __p) // _Tp1 must be complete.
    {
      // Catch self-reset errors.
      _GLIBCXX_DEBUG_ASSERT(__p == 0 || __p != _M_ptr);
      __shared_ptr(__p).swap(*this);
    }

      template<typename _Tp1, typename _Deleter>
    void
    reset(_Tp1* __p, _Deleter __d)
    { __shared_ptr(__p, __d).swap(*this); }

      template<typename _Tp1, typename _Deleter, typename _Alloc>
    void
        reset(_Tp1* __p, _Deleter __d, _Alloc __a)
        { __shared_ptr(__p, __d, std::move(__a)).swap(*this); }

      // Allow class instantiation when _Tp is [cv-qual] void.
      typename std::add_lvalue_reference<_Tp>::type
      operator*() const noexcept
      {
    _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
    return *_M_ptr;
      }

      _Tp*
      operator->() const noexcept
      {
    _GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
    return _M_ptr;
      }

      _Tp*
      get() const noexcept
      { return _M_ptr; }

      explicit operator bool() const // never throws
      { return _M_ptr == 0 ? false : true; }

      bool
      unique() const noexcept
      { return _M_refcount._M_unique(); }

      long
      use_count() const noexcept
      { return _M_refcount._M_get_use_count(); }

      void
      swap(__shared_ptr<_Tp, _Lp>& __other) noexcept
      {
    std::swap(_M_ptr, __other._M_ptr);
    _M_refcount._M_swap(__other._M_refcount);
      }

      template<typename _Tp1>
    bool
    owner_before(__shared_ptr<_Tp1, _Lp> const& __rhs) const
    { return _M_refcount._M_less(__rhs._M_refcount); }

      template<typename _Tp1>
    bool
    owner_before(__weak_ptr<_Tp1, _Lp> const& __rhs) const
    { return _M_refcount._M_less(__rhs._M_refcount); }

#ifdef __GXX_RTTI
    protected:
      // This constructor is non-standard, it is used by allocate_shared.
      template<typename _Alloc, typename... _Args>
    __shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a,
             _Args&&... __args)
    : _M_ptr(), _M_refcount(__tag, (_Tp*)0, __a,
                std::forward<_Args>(__args)...)
    {
      // _M_ptr needs to point to the newly constructed object.
      // This relies on _Sp_counted_ptr_inplace::_M_get_deleter.
      void* __p = _M_refcount._M_get_deleter(typeid(__tag));
      _M_ptr = static_cast<_Tp*>(__p);
      __enable_shared_from_this_helper(_M_refcount, _M_ptr, _M_ptr);
    }
#else
      template<typename _Alloc>
        struct _Deleter
        {
          void operator()(_Tp* __ptr)
          {
        typedef allocator_traits<_Alloc> _Alloc_traits;
        _Alloc_traits::destroy(_M_alloc, __ptr);
        _Alloc_traits::deallocate(_M_alloc, __ptr, 1);
          }
          _Alloc _M_alloc;
        };

      template<typename _Alloc, typename... _Args>
    __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);
      __enable_shared_from_this_helper(_M_refcount, _M_ptr, _M_ptr);
        }
#endif

      template<typename _Tp1, _Lock_policy _Lp1, typename _Alloc,
           typename... _Args>
    friend __shared_ptr<_Tp1, _Lp1>
    __allocate_shared(const _Alloc& __a, _Args&&... __args);

    private:
      void*
      _M_get_deleter(const std::type_info& __ti) const noexcept
      { return _M_refcount._M_get_deleter(__ti); }

      template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
      template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;

      template<typename _Del, typename _Tp1, _Lock_policy _Lp1>
    friend _Del* get_deleter(const __shared_ptr<_Tp1, _Lp1>&) noexcept;

      _Tp*         _M_ptr;         // Contained pointer.
      __shared_count<_Lp>  _M_refcount;    // Reference counter.
    };


  // 20.7.2.2.7 shared_ptr comparisons
  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
    inline bool
    operator==(const __shared_ptr<_Tp1, _Lp>& __a,
           const __shared_ptr<_Tp2, _Lp>& __b) noexcept
    { return __a.get() == __b.get(); }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
    { return !__a; }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
    { return !__a; }

  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
    inline bool
    operator!=(const __shared_ptr<_Tp1, _Lp>& __a,
           const __shared_ptr<_Tp2, _Lp>& __b) noexcept
    { return __a.get() != __b.get(); }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator!=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
    { return (bool)__a; }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator!=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
    { return (bool)__a; }

  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
    inline bool
    operator<(const __shared_ptr<_Tp1, _Lp>& __a,
          const __shared_ptr<_Tp2, _Lp>& __b) noexcept
    {
      typedef typename std::common_type<_Tp1*, _Tp2*>::type _CT;
      return std::less<_CT>()(__a.get(), __b.get());
    }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator<(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
    { return std::less<_Tp*>()(__a.get(), nullptr); }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator<(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
    { return std::less<_Tp*>()(nullptr, __a.get()); }

  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
    inline bool
    operator<=(const __shared_ptr<_Tp1, _Lp>& __a,
           const __shared_ptr<_Tp2, _Lp>& __b) noexcept
    { return !(__b < __a); }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator<=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
    { return !(nullptr < __a); }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator<=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
    { return !(__a < nullptr); }

  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
    inline bool
    operator>(const __shared_ptr<_Tp1, _Lp>& __a,
          const __shared_ptr<_Tp2, _Lp>& __b) noexcept
    { return (__b < __a); }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator>(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
    { return std::less<_Tp*>()(nullptr, __a.get()); }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator>(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
    { return std::less<_Tp*>()(__a.get(), nullptr); }

  template<typename _Tp1, typename _Tp2, _Lock_policy _Lp>
    inline bool
    operator>=(const __shared_ptr<_Tp1, _Lp>& __a,
           const __shared_ptr<_Tp2, _Lp>& __b) noexcept
    { return !(__a < __b); }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator>=(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
    { return !(__a < nullptr); }

  template<typename _Tp, _Lock_policy _Lp>
    inline bool
    operator>=(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
    { return !(nullptr < __a); }

  template<typename _Sp>
    struct _Sp_less : public binary_function<_Sp, _Sp, bool>
    {
      bool
      operator()(const _Sp& __lhs, const _Sp& __rhs) const noexcept
      {
    typedef typename _Sp::element_type element_type;
    return std::less<element_type*>()(__lhs.get(), __rhs.get());
      }
    };

  template<typename _Tp, _Lock_policy _Lp>
    struct less<__shared_ptr<_Tp, _Lp>>
    : public _Sp_less<__shared_ptr<_Tp, _Lp>>
    { };

  // 2.2.3.8 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

  // The seemingly equivalent code:
  // shared_ptr<_Tp, _Lp>(static_cast<_Tp*>(__r.get()))
  // will eventually result in undefined behaviour, attempting to
  // delete the same object twice.
  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
    inline __shared_ptr<_Tp, _Lp>
    static_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
    { return __shared_ptr<_Tp, _Lp>(__r, static_cast<_Tp*>(__r.get())); }

  // The seemingly equivalent code:
  // shared_ptr<_Tp, _Lp>(const_cast<_Tp*>(__r.get()))
  // will eventually result in undefined behaviour, attempting to
  // delete the same object twice.
  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
    inline __shared_ptr<_Tp, _Lp>
    const_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
    { return __shared_ptr<_Tp, _Lp>(__r, const_cast<_Tp*>(__r.get())); }

  // The seemingly equivalent code:
  // shared_ptr<_Tp, _Lp>(dynamic_cast<_Tp*>(__r.get()))
  // will eventually result in undefined behaviour, attempting to
  // delete the same object twice.
  template<typename _Tp, typename _Tp1, _Lock_policy _Lp>
    inline __shared_ptr<_Tp, _Lp>
    dynamic_pointer_cast(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
    {
      if (_Tp* __p = dynamic_cast<_Tp*>(__r.get()))
    return __shared_ptr<_Tp, _Lp>(__r, __p);
      return __shared_ptr<_Tp, _Lp>();
    }


  template<typename _Tp, _Lock_policy _Lp>
    class __weak_ptr
    {
    public:
      typedef _Tp element_type;

      constexpr __weak_ptr() noexcept
      : _M_ptr(0), _M_refcount()
      { }

      __weak_ptr(const __weak_ptr&) noexcept = default;
      __weak_ptr& operator=(const __weak_ptr&) noexcept = default;
      ~__weak_ptr() = default;

      // The "obvious" converting constructor implementation:
      //
      //  template<typename _Tp1>
      //    __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r)
      //    : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount) // never throws
      //    { }
      //
      // has a serious problem.
      //
      //  __r._M_ptr may already have been invalidated. The _M_ptr(__r._M_ptr)
      //  conversion may require access to *__r._M_ptr (virtual inheritance).
      //
      // It is not possible to avoid spurious access violations since
      // in multithreaded programs __r._M_ptr may be invalidated at any point.
      template<typename _Tp1, typename = typename
           std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
    __weak_ptr(const __weak_ptr<_Tp1, _Lp>& __r) noexcept
    : _M_refcount(__r._M_refcount)
        { _M_ptr = __r.lock().get(); }

      template<typename _Tp1, typename = typename
           std::enable_if<std::is_convertible<_Tp1*, _Tp*>::value>::type>
    __weak_ptr(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
    : _M_ptr(__r._M_ptr), _M_refcount(__r._M_refcount)
    { }

      template<typename _Tp1>
    __weak_ptr&
    operator=(const __weak_ptr<_Tp1, _Lp>& __r) noexcept
    {
      _M_ptr = __r.lock().get();
      _M_refcount = __r._M_refcount;
      return *this;
    }

      template<typename _Tp1>
    __weak_ptr&
    operator=(const __shared_ptr<_Tp1, _Lp>& __r) noexcept
    {
      _M_ptr = __r._M_ptr;
      _M_refcount = __r._M_refcount;
      return *this;
    }

      __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

      long
      use_count() const noexcept
      { return _M_refcount._M_get_use_count(); }

      bool
      expired() const noexcept
      { return _M_refcount._M_get_use_count() == 0; }

      template<typename _Tp1>
    bool
    owner_before(const __shared_ptr<_Tp1, _Lp>& __rhs) const
    { return _M_refcount._M_less(__rhs._M_refcount); }

      template<typename _Tp1>
    bool
    owner_before(const __weak_ptr<_Tp1, _Lp>& __rhs) const
    { return _M_refcount._M_less(__rhs._M_refcount); }

      void
      reset() noexcept
      { __weak_ptr().swap(*this); }

      void
      swap(__weak_ptr& __s) noexcept
      {
    std::swap(_M_ptr, __s._M_ptr);
    _M_refcount._M_swap(__s._M_refcount);
      }

    private:
      // Used by __enable_shared_from_this.
      void
      _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept
      {
    _M_ptr = __ptr;
    _M_refcount = __refcount;
      }

      template<typename _Tp1, _Lock_policy _Lp1> friend class __shared_ptr;
      template<typename _Tp1, _Lock_policy _Lp1> friend class __weak_ptr;
      friend class __enable_shared_from_this<_Tp, _Lp>;
      friend class enable_shared_from_this<_Tp>;

      _Tp*       _M_ptr;         // Contained pointer.
      __weak_count<_Lp>  _M_refcount;    // Reference counter.
    };

  // 20.7.2.3.6 weak_ptr specialized algorithms.
  template<typename _Tp, _Lock_policy _Lp>
    inline void
    swap(__weak_ptr<_Tp, _Lp>& __a, __weak_ptr<_Tp, _Lp>& __b) noexcept
    { __a.swap(__b); }

  template<typename _Tp, typename _Tp1>
    struct _Sp_owner_less : public binary_function<_Tp, _Tp, bool>
    {
      bool
      operator()(const _Tp& __lhs, const _Tp& __rhs) const
      { return __lhs.owner_before(__rhs); }

      bool
      operator()(const _Tp& __lhs, const _Tp1& __rhs) const
      { return __lhs.owner_before(__rhs); }

      bool
      operator()(const _Tp1& __lhs, const _Tp& __rhs) const
      { return __lhs.owner_before(__rhs); }
    };

  template<typename _Tp, _Lock_policy _Lp>
    struct owner_less<__shared_ptr<_Tp, _Lp>>
    : public _Sp_owner_less<__shared_ptr<_Tp, _Lp>, __weak_ptr<_Tp, _Lp>>
    { };

  template<typename _Tp, _Lock_policy _Lp>
    struct owner_less<__weak_ptr<_Tp, _Lp>>
    : public _Sp_owner_less<__weak_ptr<_Tp, _Lp>, __shared_ptr<_Tp, _Lp>>
    { };


  template<typename _Tp, _Lock_policy _Lp>
    class __enable_shared_from_this
    {
    protected:
      constexpr __enable_shared_from_this() noexcept { }

      __enable_shared_from_this(const __enable_shared_from_this&) noexcept { }

      __enable_shared_from_this&
      operator=(const __enable_shared_from_this&) noexcept
      { return *this; }

      ~__enable_shared_from_this() { }

    public:
      __shared_ptr<_Tp, _Lp>
      shared_from_this()
      { return __shared_ptr<_Tp, _Lp>(this->_M_weak_this); }

      __shared_ptr<const _Tp, _Lp>
      shared_from_this() const
      { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }

    private:
      template<typename _Tp1>
    void
    _M_weak_assign(_Tp1* __p, const __shared_count<_Lp>& __n) const noexcept
    { _M_weak_this._M_assign(__p, __n); }

      template<typename _Tp1>
    friend void
    __enable_shared_from_this_helper(const __shared_count<_Lp>& __pn,
                     const __enable_shared_from_this* __pe,
                     const _Tp1* __px) noexcept
    {
      if (__pe != 0)
        __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn);
    }

      mutable __weak_ptr<_Tp, _Lp>  _M_weak_this;
    };


  template<typename _Tp, _Lock_policy _Lp, typename _Alloc, typename... _Args>
    inline __shared_ptr<_Tp, _Lp>
    __allocate_shared(const _Alloc& __a, _Args&&... __args)
    {
      return __shared_ptr<_Tp, _Lp>(_Sp_make_shared_tag(), __a,
                    std::forward<_Args>(__args)...);
    }

  template<typename _Tp, _Lock_policy _Lp, typename... _Args>
    inline __shared_ptr<_Tp, _Lp>
    __make_shared(_Args&&... __args)
    {
      typedef typename std::remove_const<_Tp>::type _Tp_nc;
      return std::__allocate_shared<_Tp, _Lp>(std::allocator<_Tp_nc>(),
                          std::forward<_Args>(__args)...);
    }

  template<typename _Tp, _Lock_policy _Lp>
    struct hash<__shared_ptr<_Tp, _Lp>>
    : public __hash_base<size_t, __shared_ptr<_Tp, _Lp>>
    {
      size_t
      operator()(const __shared_ptr<_Tp, _Lp>& __s) const noexcept
      { return std::hash<_Tp*>()(__s.get()); }
    };

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

template<typename _Ex >

exception_ptr std::copy_exception

(

_Ex

__ex

)

Obtain an exception_ptr pointing to a copy of the supplied object.

    {
      __try
    {
#ifdef __EXCEPTIONS
      throw __ex;
#endif
    }
      __catch(...)
    {
      return current_exception();
    }
    }

exception_ptr std::current_exception

(

)

Obtain an exception_ptr to the currently handled exception. If there is none, or the currently handled exception is foreign, return the null value.

template<typename _Ex >

exception_ptr std::make_exception_ptr

(

_Ex

__ex

)

Obtain an exception_ptr pointing to a copy of the supplied object.

    { return std::copy_exception<_Ex>(__ex); }

void std::rethrow_exception

(

exception_ptr

)

Throw the object pointed to by the exception_ptr.

terminate_handler std::set_terminate

(

terminate_handler

)

Takes a new handler function as an argument, returns the old function.

unexpected_handler std::set_unexpected

(

unexpected_handler

)

Takes a new handler function as an argument, returns the old function.

void std::terminate

(

)

The runtime will call this function if exception handling must be abandoned for any reason. It can also be called by the user.

bool std::uncaught_exception

(

)

[18.6.4]/1: 'Returns true after completing evaluation of a throw-expression until either completing initialization of the exception-declaration in the matching handler or entering unexpected() due to the throw; or after entering terminate() for any reason other than an explicit call to terminate(). [Note: This includes stack unwinding [15.2]. end note]'

2: 'When uncaught_exception() is true, throwing an exception can result in a call of terminate() (15.5.1).'

void std::unexpected

(

)

The runtime will call this function if an exception is thrown which violates the function's exception specification.