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PR libstdc++/79254 fix exception-safety in std::string::operator=

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PR libstdc++/79254
	* config/abi/pre/gnu.ver: Add new symbols.
	* include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
	(basic_string::_M_copy_assign): New overloaded functions to perform
	copy assignment.
	(basic_string::operator=(const basic_string&)): Dispatch to
	_M_copy_assign.
	* include/bits/basic_string.tcc [_GLIBCXX_USE_CXX11_ABI]
	(basic_string::_M_copy_assign(const basic_string&, true_type)):
	Define, performing rollback on exception.
	* testsuite/21_strings/basic_string/allocator/char/copy_assign.cc:
	Test exception-safety guarantee.
	* testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc:
	Likewise.
	* testsuite/util/testsuite_allocator.h (uneq_allocator::swap): Make
	std::swap visible.

From-SVN: r244986
This commit is contained in:
Jonathan Wakely 2017-01-27 16:17:04 +00:00 • committed by Jonathan Wakely
parent f75bbf3fc6
commit a7d47f3526
7 changed files with 155 additions and 16 deletions
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19
libstdc++-v3/ChangeLog
View file

@ -1,3 +1,22 @@
2017-01-27 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/79254
* config/abi/pre/gnu.ver: Add new symbols.
* include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
(basic_string::_M_copy_assign): New overloaded functions to perform
copy assignment.
(basic_string::operator=(const basic_string&)): Dispatch to
_M_copy_assign.
* include/bits/basic_string.tcc [_GLIBCXX_USE_CXX11_ABI]
(basic_string::_M_copy_assign(const basic_string&, true_type)):
Define, performing rollback on exception.
* testsuite/21_strings/basic_string/allocator/char/copy_assign.cc:
Test exception-safety guarantee.
* testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc:
Likewise.
* testsuite/util/testsuite_allocator.h (uneq_allocator::swap): Make
std::swap visible.
2017-01-26 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/70607

7
libstdc++-v3/config/abi/pre/gnu.ver
View file

@ -1700,7 +1700,9 @@ GLIBCXX_3.4.21 {
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE1[01]**;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE12_Alloc_hiderC[12]EP[cw]RKS3_;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE12_M*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE1[3-9]*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE13*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE14_M_replace_aux*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE1[5-9]*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE[2-9]*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]EOS4_*;
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EEC[12]EPK*;
@ -1953,6 +1955,9 @@ GLIBCXX_3.4.23 {
_ZNSsC[12]ERKSs[jmy]RKSaIcE;
_ZNSbIwSt11char_traitsIwESaIwEEC[12]ERKS2_mRKS1_;
# basic_string<C, T, A>::_M_copy_assign(const basic_string&, {true,false}_type)
_ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE14_M_copy_assign*;
#ifndef HAVE_EXCEPTION_PTR_SINCE_GCC46
# std::future symbols are exported in the first version to support
# std::exception_ptr

29
libstdc++-v3/include/bits/basic_string.h
View file

@ -384,7 +384,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
}
void
_M_assign(const basic_string& __rcs);
_M_assign(const basic_string&);
void
_M_mutate(size_type __pos, size_type __len1, const _CharT* __s,
@ -393,6 +393,15 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
void
_M_erase(size_type __pos, size_type __n);
#if __cplusplus >= 201103L
void
_M_copy_assign(const basic_string& __str, /* pocca = */ true_type);
void
_M_copy_assign(const basic_string& __str, /* pocca = */ false_type)
{ this->_M_assign(__str); }
#endif
public:
// Construct/copy/destroy:
// NB: We overload ctors in some cases instead of using default
@ -627,20 +636,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
operator=(const basic_string& __str)
{
#if __cplusplus >= 201103L
if (_Alloc_traits::_S_propagate_on_copy_assign())
{
if (!_Alloc_traits::_S_always_equal() && !_M_is_local()
&& _M_get_allocator() != __str._M_get_allocator())
{
// replacement allocator cannot free existing storage
_M_destroy(_M_allocated_capacity);
_M_data(_M_local_data());
_M_set_length(0);
}
std::__alloc_on_copy(_M_get_allocator(), __str._M_get_allocator());
}
_M_copy_assign(__str,
typename _Alloc_traits::propagate_on_container_copy_assignment());
#else
this->_M_assign(__str);
#endif
return this->assign(__str);
return *this;
}
/**

64
libstdc++-v3/include/bits/basic_string.tcc
View file

@ -275,6 +275,70 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
}
#if __cplusplus >= 201103L
template<typename _CharT, typename _Traits, typename _Alloc>
void
basic_string<_CharT, _Traits, _Alloc>::
_M_copy_assign(const basic_string& __str, true_type)
{
struct _Guard // RAII type for strong exception-safety guarantee.
{
// Takes ownership of string's original state.
_Guard(basic_string* __self)
: _M_self(__self), _M_alloc(std::move(__self->_M_get_allocator())),
_M_ptr(__self->_M_data()),
_M_capacity(__self->_M_allocated_capacity), _M_len(__self->length())
{
__self->_M_data(__self->_M_local_data());
__self->_M_length(0);
}
// Restores string's original state if _M_release() was not called.
~_Guard()
{
if (_M_ptr)
{
_M_self->_M_get_allocator() = std::move(_M_alloc);
_M_self->_M_data(_M_ptr);
_M_self->_M_capacity(_M_capacity);
_M_self->_M_length(_M_len);
}
}
_Guard(const _Guard&) = delete;
_Guard& operator=(const _Guard&) = delete;
void _M_release()
{
// Original state can be freed now.
_Alloc_traits::deallocate(_M_alloc, _M_ptr, _M_capacity + 1);
_M_ptr = nullptr;
}
basic_string* _M_self;
allocator_type _M_alloc;
pointer _M_ptr;
size_type _M_capacity;
size_type _M_len;
};
if (!_Alloc_traits::_S_always_equal() && !_M_is_local()
&& _M_get_allocator() != __str._M_get_allocator())
{
// The propagating allocator cannot free existing storage.
_Guard __guard(this);
_M_get_allocator() = __str._M_get_allocator();
this->_M_assign(__str);
__guard._M_release();
}
else
{
_M_get_allocator() = __str._M_get_allocator();
this->_M_assign(__str);
}
}
#endif
template<typename _CharT, typename _Traits, typename _Alloc>
void
basic_string<_CharT, _Traits, _Alloc>::

25
libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/copy_assign.cc
View file

@ -22,6 +22,7 @@
#include <string>
#include <testsuite_hooks.h>
#include <testsuite_allocator.h>
#include <ext/throw_allocator.h>
using C = char;
const C c = 'a';
@ -99,9 +100,33 @@ void test02()
VERIFY(1 == v5.get_allocator().get_personality());
}
void test03()
{
// PR libstdc++/79254
using throw_alloc = __gnu_cxx::throw_allocator_limit<C>;
typedef propagating_allocator<C, true, throw_alloc> alloc_type;
typedef std::basic_string<C, traits, alloc_type> test_type;
alloc_type a1(1), a2(2);
throw_alloc::set_limit(2); // Throw on third allocation (during assignment).
const C* s1 = "a string that is longer than a small string";
const C* s2 = "another string that is longer than a small string";
test_type v1(s1, a1);
test_type v2(s2, a2);
bool caught = false;
try {
v1 = v2;
} catch (__gnu_cxx::forced_error&) {
caught = true;
}
VERIFY( caught );
VERIFY( v1 == s1 );
VERIFY( v1.get_allocator() == a1 );
}
int main()
{
test01();
test02();
test03();
return 0;
}

25
libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/copy_assign.cc
View file

@ -22,6 +22,7 @@
#include <string>
#include <testsuite_hooks.h>
#include <testsuite_allocator.h>
#include <ext/throw_allocator.h>
using C = wchar_t;
const C c = L'a';
@ -99,9 +100,33 @@ void test02()
VERIFY(1 == v5.get_allocator().get_personality());
}
void test03()
{
// PR libstdc++/79254
using throw_alloc = __gnu_cxx::throw_allocator_limit<C>;
typedef propagating_allocator<C, true, throw_alloc> alloc_type;
typedef std::basic_string<C, traits, alloc_type> test_type;
alloc_type a1(1), a2(2);
throw_alloc::set_limit(2); // Throw on third allocation (during assignment).
const C* s1 = L"a string that is longer than a small string";
const C* s2 = L"another string that is longer than a small string";
test_type v1(s1, a1);
test_type v2(s2, a2);
bool caught = false;
try {
v1 = v2;
} catch (__gnu_cxx::forced_error&) {
caught = true;
}
VERIFY( caught );
VERIFY( v1 == s1 );
VERIFY( v1.get_allocator() == a1 );
}
int main()
{
test01();
test02();
test03();
return 0;
}

2
libstdc++-v3/testsuite/util/testsuite_allocator.h
View file

@ -287,7 +287,7 @@ namespace __gnu_test
Alloc& base() { return *this; }
const Alloc& base() const { return *this; }
void swap_base(Alloc& b) { swap(b, this->base()); }
void swap_base(Alloc& b) { using std::swap; swap(b, this->base()); }
public:
typedef typename check_consistent_alloc_value_type<Tp, Alloc>::value_type