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

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

include/memory

@@ -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;

include/vector

@@ -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());

test/libcxx/containers/sequences/vector/exception_safety_exceptions_disabled.sh.cpp

@@ -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;
-}