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[libc++] Revert "Make vector unconditionally move elements when exceptions are disabled."

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This reverts r370502, which broke the use case of a copy-only T (with a
deleted move constructor) when exceptions are disabled. Until we figure
out the right behavior, I'm reverting the commit.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@371068 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Louis Dionne
2019-09-05 13:50:28 +00:00
parent 7de36b7778
commit ffced82bd0
3 changed files with 10 additions and 82 deletions
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26
include/memory
View File

@@ -1609,16 +1609,10 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
_LIBCPP_INLINE_VISIBILITY
static
void
__construct_forward_with_exception_guarantees(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __begin2)
__construct_forward(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __begin2)
{
for (; __begin1 != __end1; ++__begin1, (void) ++__begin2)
construct(__a, _VSTD::__to_raw_pointer(__begin2),
#ifdef _LIBCPP_NO_EXCEPTIONS
_VSTD::move(*__begin1)
#else
_VSTD::move_if_noexcept(*__begin1)
#endif
);
construct(__a, _VSTD::__to_raw_pointer(__begin2), _VSTD::move_if_noexcept(*__begin1));
}
template <class _Tp>
@@ -1631,7 +1625,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
is_trivially_move_constructible<_Tp>::value,
void
>::type
__construct_forward_with_exception_guarantees(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
__construct_forward(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
{
ptrdiff_t _Np = __end1 - __begin1;
if (_Np > 0)
@@ -1678,18 +1672,12 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
_LIBCPP_INLINE_VISIBILITY
static
void
__construct_backward_with_exception_guarantees(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __end2)
__construct_backward(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __end2)
{
while (__end1 != __begin1)
{
construct(__a, _VSTD::__to_raw_pointer(__end2 - 1),
#ifdef _LIBCPP_NO_EXCEPTIONS
_VSTD::move(*--__end1)
#else
_VSTD::move_if_noexcept(*--__end1)
#endif
);
--__end2;
construct(__a, _VSTD::__to_raw_pointer(__end2-1), _VSTD::move_if_noexcept(*--__end1));
--__end2;
}
}
@@ -1703,7 +1691,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
is_trivially_move_constructible<_Tp>::value,
void
>::type
__construct_backward_with_exception_guarantees(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __end2)
__construct_backward(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __end2)
{
ptrdiff_t _Np = __end1 - __begin1;
__end2 -= _Np;

9
include/vector
View File

@@ -948,8 +948,7 @@ void
vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, allocator_type&>& __v)
{
__annotate_delete();
__alloc_traits::__construct_backward_with_exception_guarantees(
this->__alloc(), this->__begin_, this->__end_, __v.__begin_);
__alloc_traits::__construct_backward(this->__alloc(), this->__begin_, this->__end_, __v.__begin_);
_VSTD::swap(this->__begin_, __v.__begin_);
_VSTD::swap(this->__end_, __v.__end_);
_VSTD::swap(this->__end_cap(), __v.__end_cap());
@@ -964,10 +963,8 @@ vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, a
{
__annotate_delete();
pointer __r = __v.__begin_;
__alloc_traits::__construct_backward_with_exception_guarantees(
this->__alloc(), this->__begin_, __p, __v.__begin_);
__alloc_traits::__construct_forward_with_exception_guarantees(
this->__alloc(), __p, this->__end_, __v.__end_);
__alloc_traits::__construct_backward(this->__alloc(), this->__begin_, __p, __v.__begin_);
__alloc_traits::__construct_forward(this->__alloc(), __p, this->__end_, __v.__end_);
_VSTD::swap(this->__begin_, __v.__begin_);
_VSTD::swap(this->__end_, __v.__end_);
_VSTD::swap(this->__end_cap(), __v.__end_cap());

57
test/libcxx/containers/sequences/vector/exception_safety_exceptions_disabled.sh.cpp
View File

@@ -1,57 +0,0 @@
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// RUN: %build -fno-exceptions
// RUN: %run
// UNSUPPORTED: c++98, c++03
// <vector>
// Test that vector always moves elements when exceptions are disabled.
// vector is allowed to move or copy elements while resizing, so long as
// it still provides the strong exception safety guarantee.
#include <vector>
#include <cassert>
#include "test_macros.h"
#ifndef TEST_HAS_NO_EXCEPTIONS
#error exceptions should be disabled.
#endif
bool allow_moves = false;
class A {
public:
A() {}
A(A&&) { assert(allow_moves); }
explicit A(int) {}
A(A const&) { assert(false); }
};
int main(int, char**) {
std::vector<A> v;
// Create a vector containing some number of elements that will
// have to be moved when it is resized.
v.reserve(10);
size_t old_cap = v.capacity();
for (int i = 0; i < v.capacity(); ++i) {
v.emplace_back(42);
}
assert(v.capacity() == old_cap);
assert(v.size() == v.capacity());
// The next emplace back should resize.
allow_moves = true;
v.emplace_back(42);
return 0;
}