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re PR libstdc++/3946 (auto_ptr_ref constructor allows dangerous conversion)

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2002-07-03  Jack Reeves  <jackw_reeves@hotmail.com>
            Kenny Simpson  <theonetruekenny@yahoo.com>
            Phil Edwards  <pme@gcc.gnu.org>

	PR libstdc++/3946
	* testsuite/20_util/auto_ptr.cc (test08):  New test.
	* include/std/std_memory.h (auto_ref_ptr):  Make constructor explicit.
	(auto_ptr::operator auto_ptr_ref):  Fix typo.
	General reformatting and doxygenating of the whole file.

Co-Authored-By: Kenny Simpson <theonetruekenny@yahoo.com>
Co-Authored-By: Phil Edwards <pme@gcc.gnu.org>

From-SVN: r55223
This commit is contained in:
Jack Reeves 2002-07-03 22:25:06 +00:00 committed by Phil Edwards
parent 6f0361e32e
commit 16ad69a19d
3 changed files with 297 additions and 104 deletions
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10
libstdc++-v3/ChangeLog
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@ -1,3 +1,13 @@
2002-07-03 Jack Reeves <jackw_reeves@hotmail.com>
Kenny Simpson <theonetruekenny@yahoo.com>
Phil Edwards <pme@gcc.gnu.org>
PR libstdc++/3946
* testsuite/20_util/auto_ptr.cc (test08): New test.
* include/std/std_memory.h (auto_ref_ptr): Make constructor explicit.
(auto_ptr::operator auto_ptr_ref): Fix typo.
General reformatting and doxygenating of the whole file.
2002-07-03 Benjamin Kosnik <bkoz@redhat.com>
PR libstdc++/7097

373
libstdc++-v3/include/std/std_memory.h
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@ -58,147 +58,314 @@
#include <bits/stl_uninitialized.h>
#include <bits/stl_raw_storage_iter.h>
// Since this entire file is within namespace std, there's no reason to
// waste two spaces along the left column. Thus the leading indentation is
// slightly violated from here on.
namespace std
{
/**
* @if maint
* This is a helper function. The unused second parameter exists to
* permit the real get_temporary_buffer to use template parameter deduction.
*
* XXX This should perhaps use the pool.
* @endif
*/
template <typename _Tp>
pair<_Tp*, ptrdiff_t>
__get_temporary_buffer(ptrdiff_t __len, _Tp*)
{
if (__len > ptrdiff_t(INT_MAX / sizeof(_Tp)))
__len = INT_MAX / sizeof(_Tp);
/**
* @if maint
* This is a helper function. The unused second parameter exists to
* permit the real get_temporary_buffer to use template parameter deduction.
* @endif
*/
template <class _Tp>
pair<_Tp*, ptrdiff_t>
__get_temporary_buffer(ptrdiff_t __len, _Tp*)
{
if (__len > ptrdiff_t(INT_MAX / sizeof(_Tp)))
__len = INT_MAX / sizeof(_Tp);
while (__len > 0) {
_Tp* __tmp = (_Tp*) std::malloc((std::size_t)__len * sizeof(_Tp));
if (__tmp != 0)
return pair<_Tp*, ptrdiff_t>(__tmp, __len);
__len /= 2;
}
return pair<_Tp*, ptrdiff_t>((_Tp*)0, 0);
while (__len > 0) {
_Tp* __tmp = (_Tp*) std::malloc((std::size_t)__len * sizeof(_Tp));
if (__tmp != 0)
return pair<_Tp*, ptrdiff_t>(__tmp, __len);
__len /= 2;
}
/**
* @brief This is a mostly-useless wrapper around malloc().
* @param len The number of objects of type Tp.
* @return See full description.
*
* Reinventing the wheel, but this time with prettier spokes!
*
* This function tries to obtain storage for @c len adjacent Tp objects.
* The objects themselves are not constructed, of course. A pair<> is
* returned containing "the buffer s address and capacity (in the units of
* sizeof(Tp)), or a pair of 0 values if no storage can be obtained."
* Note that the capacity obtained may be less than that requested if the
* memory is unavailable; you should compare len with the .second return
* value.
*/
template <class _Tp>
inline pair<_Tp*, ptrdiff_t> get_temporary_buffer(ptrdiff_t __len) {
return pair<_Tp*, ptrdiff_t>((_Tp*)0, 0);
}
/**
* @brief This is a mostly-useless wrapper around malloc().
* @param len The number of objects of type Tp.
* @return See full description.
*
* Reinventing the wheel, but this time with prettier spokes!
*
* This function tries to obtain storage for @c len adjacent Tp objects.
* The objects themselves are not constructed, of course. A pair<> is
* returned containing "the buffer s address and capacity (in the units of
* sizeof(Tp)), or a pair of 0 values if no storage can be obtained."
* Note that the capacity obtained may be less than that requested if the
* memory is unavailable; you should compare len with the .second return
* value.
*/
template<typename _Tp>
inline pair<_Tp*,ptrdiff_t>
get_temporary_buffer(ptrdiff_t __len)
{
return __get_temporary_buffer(__len, (_Tp*) 0);
}
/**
* @brief The companion to get_temporary_buffer().
* @param p A buffer previously allocated by get_temporary_buffer.
* @return None.
*
* Frees the memory pointed to by p.
*/
template <class _Tp>
void return_temporary_buffer(_Tp* __p) {
/**
* @brief The companion to get_temporary_buffer().
* @param p A buffer previously allocated by get_temporary_buffer.
* @return None.
*
* Frees the memory pointed to by p.
*/
template<typename _Tp>
void
return_temporary_buffer(_Tp* __p)
{
std::free(__p);
}
template <class _Tp1>
/**
* A wrapper class to provide auto_ptr with reference semantics. For
* example, an auto_ptr can be assigned (or constructed from) the result of
* a function which returns an auto_ptr by value.
*
* All the auto_ptr_ref stuff should happen behind the scenes.
*/
template<typename _Tp1>
struct auto_ptr_ref
{
_Tp1* _M_ptr;
auto_ptr_ref(_Tp1* __p) : _M_ptr(__p) {}
explicit
auto_ptr_ref(_Tp1* __p)
: _M_ptr(__p) {}
};
/**
* A simple smart pointer providing strict ownership semantics. (More later.)
* @brief A simple smart pointer providing strict ownership semantics.
*
* The Standard says:
* <pre>
* An @c auto_ptr owns the object it holds a pointer to. Copying an
* @c auto_ptr copies the pointer and transfers ownership to the destination.
* If more than one @c auto_ptr owns the same object at the same time the
* behavior of the program is undefined.
*
* The uses of @c auto_ptr include providing temporary exception-safety for
* dynamically allocated memory, passing ownership of dynamically allocated
* memory to a function, and returning dynamically allocated memory from a
* function. @c auto_ptr does not meet the CopyConstructible and Assignable
* requirements for Standard Library <a href="tables.html#65">container</a>
* elements and thus instantiating a Standard Library container with an
* @c auto_ptr results in undefined behavior.
* </pre>
* Quoted from [20.4.5]/3.
*
* Good examples of what can and cannot be done with auto_ptr can be found
* in the libstdc++ testsuite.
*
* @if maint
* _GLIBCPP_RESOLVE_LIB_DEFECTS
* 127. auto_ptr<> conversion issues
* These resolutions have all been incorporated.
* @endif
*/
template <class _Tp>
template<typename _Tp>
class auto_ptr
{
private:
_Tp* _M_ptr;
public:
/// The pointed-to type.
typedef _Tp element_type;
explicit auto_ptr(_Tp* __p = 0) throw() : _M_ptr(__p) {}
auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) {}
/**
* @brief An %auto_ptr is usually constructed from a raw pointer.
* @param p A pointer (defaults to NULL).
*
* This object now @e owns the object pointed to by @a p.
*/
explicit
auto_ptr(element_type* __p = 0) throw()
: _M_ptr(__p) { }
template <class _Tp1> auto_ptr(auto_ptr<_Tp1>& __a) throw()
: _M_ptr(__a.release()) {}
/**
* @brief An %auto_ptr can be constructed from another %auto_ptr.
* @param a Another %auto_ptr of the same type.
*
* This object now @e owns the object previously owned by @a a, which has
* given up ownsership.
*/
auto_ptr(auto_ptr& __a) throw()
: _M_ptr(__a.release()) { }
auto_ptr& operator=(auto_ptr& __a) throw() {
reset(__a.release());
return *this;
}
/**
* @brief An %auto_ptr can be constructed from another %auto_ptr.
* @param a Another %auto_ptr of a different but related type.
*
* A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
*
* This object now @e owns the object previously owned by @a a, which has
* given up ownsership.
*/
template<typename _Tp1>
auto_ptr(auto_ptr<_Tp1>& __a) throw()
: _M_ptr(__a.release()) { }
template <class _Tp1>
auto_ptr& operator=(auto_ptr<_Tp1>& __a) throw() {
reset(__a.release());
return *this;
}
// Note: The C++ standard says there is supposed to be an empty throw
// specification here, but omitting it is standard conforming. Its
// presence can be detected only if _Tp::~_Tp() throws, but (17.4.3.6/2)
// this is prohibited.
/**
* @brief %auto_ptr assignment operator.
* @param a Another %auto_ptr of the same type.
*
* This object now @e owns the object previously owned by @a a, which has
* given up ownsership. The object that this one @e used to own and
* track has been deleted.
*/
auto_ptr&
operator=(auto_ptr& __a) throw()
{
reset(__a.release());
return *this;
}
/**
* @brief %auto_ptr assignment operator.
* @param a Another %auto_ptr of a different but related type.
*
* A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
*
* This object now @e owns the object previously owned by @a a, which has
* given up ownsership. The object that this one @e used to own and
* track has been deleted.
*/
template <typename _Tp1>
auto_ptr&
operator=(auto_ptr<_Tp1>& __a) throw()
{
reset(__a.release());
return *this;
}
/**
* When the %auto_ptr goes out of scope, the object it owns is deleted.
* If it no longer owns anything (i.e., @c get() is @c NULL), then this
* has no effect.
*
* @if maint
* The C++ standard says there is supposed to be an empty throw
* specification here, but omitting it is standard conforming. Its
* presence can be detected only if _Tp::~_Tp() throws, but this is
* prohibited. [17.4.3.6]/2
* @end maint
*/
~auto_ptr() { delete _M_ptr; }
_Tp& operator*() const throw() {
return *_M_ptr;
}
_Tp* operator->() const throw() {
return _M_ptr;
}
_Tp* get() const throw() {
return _M_ptr;
}
_Tp* release() throw() {
_Tp* __tmp = _M_ptr;
_M_ptr = 0;
return __tmp;
}
void reset(_Tp* __p = 0) throw() {
if (__p != _M_ptr) {
delete _M_ptr;
_M_ptr = __p;
}
}
public:
auto_ptr(auto_ptr_ref<_Tp> __ref) throw()
/**
* @brief Smart pointer dereferencing.
*
* If this %auto_ptr no longer owns anything, then this operation will
* crash. (For a smart pointer, "no longer owns anything" is the same as
* being a null pointer, and you know what happens when you dereference
* one of those...)
*/
element_type&
operator*() const throw() { return *_M_ptr; }
/**
* @brief Smart pointer dereferencing.
*
* This returns the pointer itself, which the language then will
* automatically cause to be dereferenced.
*/
element_type*
operator->() const throw() { return _M_ptr; }
/**
* @brief Bypassing the smart pointer.
* @return The raw pointer being managed.
*
* You can get a copy of the pointer that this object owns, for
* situations such as passing to a function which only accepts a raw
* pointer.
*
* @note This %auto_ptr still owns the memory.
*/
element_type*
get() const throw() { return _M_ptr; }
/**
* @brief Bypassing the smart pointer.
* @return The raw pointer being managed.
*
* You can get a copy of the pointer that this object owns, for
* situations such as passing to a function which only accepts a raw
* pointer.
*
* @note This %auto_ptr no longer owns the memory. When this object
* goes out of scope, nothing will happen.
*/
element_type*
release() throw()
{
element_type* __tmp = _M_ptr;
_M_ptr = 0;
return __tmp;
}
/**
* @brief Forcibly deletes the managed object.
* @param p A pointer (defaults to NULL).
*
* This object now @e owns the object pointed to by @a p. The previous
* object has been deleted.
*/
void
reset(element_type* __p = 0) throw()
{
if (__p != _M_ptr)
{
delete _M_ptr;
_M_ptr = __p;
}
}
/** @{
* @brief Automatic conversions
*
* These operations convert an %auto_ptr into and from an auto_ptr_ref
* automatically as needed. This allows constructs such as
* @code
* auto_ptr<Derived> func_returning_auto_ptr(.....);
* ...
* auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
* @endcode
*/
auto_ptr(auto_ptr_ref<element_type> __ref) throw()
: _M_ptr(__ref._M_ptr) {}
auto_ptr& operator=(auto_ptr_ref<_Tp> __ref) throw() {
if (__ref._M_ptr != this->get()) {
delete _M_ptr;
_M_ptr = __ref._M_ptr;
auto_ptr&
operator=(auto_ptr_ref<element_type> __ref) throw()
{
if (__ref._M_ptr != this->get())
{
delete _M_ptr;
_M_ptr = __ref._M_ptr;
}
return *this;
}
return *this;
}
template <class _Tp1> operator auto_ptr_ref<_Tp1>() throw()
{ return auto_ptr_ref<_Tp>(this->release()); }
template <class _Tp1> operator auto_ptr<_Tp1>() throw()
{ return auto_ptr<_Tp1>(this->release()); }
template<typename _Tp1>
operator auto_ptr_ref<_Tp1>() throw()
{ return auto_ptr_ref<_Tp1>(this->release()); }
template<typename _Tp1>
operator auto_ptr<_Tp1>() throw()
{ return auto_ptr<_Tp1>(this->release()); }
/** @} */
};
} // namespace std
#endif /* _CPP_MEMORY */

18
libstdc++-v3/testsuite/20_util/auto_ptr.cc
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@ -1,4 +1,4 @@
// Copyright (C) 2000 Free Software Foundation
// Copyright (C) 2000, 2002 Free Software Foundation
//
// 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
@ -276,6 +276,21 @@ test07()
return 0;
}
// http://gcc.gnu.org/ml/libstdc++/2002-07/msg00024.html
struct Base{};
struct Derived : public Base {};
std::auto_ptr<Derived> conversiontest08()
{ return std::auto_ptr<Derived>(new Derived); }
void
test08()
{
std::auto_ptr<Base> ptr;
ptr = conversiontest08();
}
int
main()
{
@ -286,6 +301,7 @@ main()
test05();
test06();
test07();
test08();
return 0;
}