Avoid reallocation for basic_string::clear()
PR libstdc++/56166 PR libstdc++/77582 * include/bits/basic_string.h (basic_string::clear()): Drop reference and use empty rep. * include/ext/rc_string_base.h (__rc_string_base::_M_clear()): Likewise. * testsuite/21_strings/basic_string/56166.cc: New. * testsuite/ext/vstring/modifiers/clear/56166.cc: New. From-SVN: r240447
This commit is contained in:
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@ -1,5 +1,14 @@
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2016-09-23 Jonathan Wakely <jwakely@redhat.com>
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2016-09-23 Jonathan Wakely <jwakely@redhat.com>
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PR libstdc++/56166
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PR libstdc++/77582
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* include/bits/basic_string.h (basic_string::clear()): Drop reference
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and use empty rep.
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* include/ext/rc_string_base.h (__rc_string_base::_M_clear()):
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Likewise.
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* testsuite/21_strings/basic_string/56166.cc: New.
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* testsuite/ext/vstring/modifiers/clear/56166.cc: New.
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* include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
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* include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
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(basic_string::erase(size_type, size_type)): Add fast path for
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(basic_string::erase(size_type, size_type)): Add fast path for
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truncating the string, by calling _M_set_length directly.
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truncating the string, by calling _M_set_length directly.
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@ -3690,10 +3690,24 @@ _GLIBCXX_END_NAMESPACE_CXX11
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/**
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/**
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* Erases the string, making it empty.
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* Erases the string, making it empty.
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*/
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*/
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#if _GLIBCXX_FULLY_DYNAMIC_STRING == 0
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void
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clear() _GLIBCXX_NOEXCEPT
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{
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if (_M_rep()->_M_is_shared())
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{
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_M_rep()->_M_dispose(this->get_allocator());
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_M_data(_S_empty_rep()._M_refdata());
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}
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else
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_M_rep()->_M_set_length_and_sharable(0);
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}
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#else
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// PR 56166: this should not throw.
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// PR 56166: this should not throw.
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void
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void
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clear()
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clear()
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{ _M_mutate(0, this->size(), 0); }
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{ _M_mutate(0, this->size(), 0); }
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#endif
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/**
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/**
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* Returns true if the %string is empty. Equivalent to
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* Returns true if the %string is empty. Equivalent to
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@ -354,7 +354,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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void
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void
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_M_clear()
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_M_clear()
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{ _M_erase(size_type(0), _M_length()); }
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{
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_M_dispose();
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_M_data(_S_empty_rep._M_refcopy());
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}
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bool
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bool
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_M_compare(const __rc_string_base&) const
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_M_compare(const __rc_string_base&) const
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@ -0,0 +1,93 @@
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// Copyright (C) 2016 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License along
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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// { dg-do run { target c++11 } }
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// libstdc++/56166
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#ifndef _GLIBCXX_USE_CXX11_ABI
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# define _GLIBCXX_USE_CXX11_ABI 0
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#endif
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#include <string>
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#include <new>
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static int fail_after = -1;
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template<typename T>
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struct Allocator
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{
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using value_type = T;
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// Need these typedefs because COW string doesn't use allocator_traits.
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using pointer = T*;
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using const_pointer = const T*;
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using reference = T&;
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using const_reference = const T&;
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using difference_type = long;
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using size_type = unsigned long;
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template<typename U>
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struct rebind {
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using other = Allocator<U>;
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};
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Allocator() { }
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template<typename U>
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Allocator(const Allocator<U>&) { }
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T* allocate(size_type n)
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{
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if (fail_after >= 0) {
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if (fail_after-- == 0) {
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throw std::bad_alloc();
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}
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}
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return (T*)new char[n * sizeof(T)];
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}
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void deallocate(T* p, size_type)
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{
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delete[] (char*)p;
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}
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};
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template<typename T, typename U>
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bool operator==(const Allocator<T>&, const Allocator<U>&) { return true; }
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template<typename T, typename U>
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bool operator!=(const Allocator<T>&, const Allocator<U>&) { return false; }
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using string = std::basic_string<char, std::char_traits<char>, Allocator<char>>;
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string f()
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{
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string s1("xxxxxx");
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string s2 = s1;
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s1.clear();
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return s2;
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}
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int main()
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{
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for (int i = 0; i < 10; i++) {
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try {
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fail_after = i;
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f();
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break;
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} catch (std::bad_alloc) {
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}
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}
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}
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@ -0,0 +1,96 @@
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// Copyright (C) 2016 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License along
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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// { dg-do run { target c++11 } }
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// libstdc++/56166
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#ifndef _GLIBCXX_USE_CXX11_ABI
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# define _GLIBCXX_USE_CXX11_ABI 0
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#endif
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#include <ext/vstring.h>
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#include <new>
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static int fail_after = -1;
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template<typename T>
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struct Allocator
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{
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using value_type = T;
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// Need these typedefs because COW string doesn't use allocator_traits.
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using pointer = T*;
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using const_pointer = const T*;
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using reference = T&;
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using const_reference = const T&;
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using difference_type = long;
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using size_type = unsigned long;
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template<typename U>
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struct rebind {
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using other = Allocator<U>;
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};
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Allocator() { }
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template<typename U>
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Allocator(const Allocator<U>&) { }
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T* allocate(size_type n)
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{
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if (fail_after >= 0) {
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if (fail_after-- == 0) {
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throw std::bad_alloc();
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}
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}
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return (T*)new char[n * sizeof(T)];
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}
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void deallocate(T* p, size_type)
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{
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delete[] (char*)p;
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}
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};
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template<typename T, typename U>
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bool operator==(const Allocator<T>&, const Allocator<U>&) { return true; }
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template<typename T, typename U>
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bool operator!=(const Allocator<T>&, const Allocator<U>&) { return false; }
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using string = __gnu_cxx::__versa_string<char, std::char_traits<char>,
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Allocator<char>,
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__gnu_cxx::__rc_string_base>;
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string f()
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{
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string s1("xxxxxx");
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string s2 = s1;
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s1.clear();
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return s2;
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}
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int main()
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{
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for (int i = 0; i < 10; i++) {
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try {
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fail_after = i;
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f();
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break;
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} catch (std::bad_alloc) {
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}
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}
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}
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