+2018-10-25 Jonathan Wakely <jwakely@redhat.com>
+
+ PR libstdc++/87749
+ * include/bits/basic_string.h [_GLIBCXX_USE_CXX11_ABI]
+ (basic_string::operator=(basic_string&&)): For short strings copy the
+ buffer inline. Only fall back to using assign(const basic_string&) to
+ do a deep copy when reallocation is needed.
+ * testsuite/21_strings/basic_string/modifiers/assign/char/87749.cc:
+ New test.
+ * testsuite/21_strings/basic_string/modifiers/assign/char/
+ move_assign_optim.cc: New test.
+ * testsuite/21_strings/basic_string/modifiers/assign/wchar_t/87749.cc:
+ New test.
+ * testsuite/21_strings/basic_string/modifiers/assign/wchar_t/
+ move_assign_optim.cc: New test.
+
2018-10-25 Jonathan Wakely <jwakely@redhat.com>
// Replace allocator if POCMA is true.
std::__alloc_on_move(_M_get_allocator(), __str._M_get_allocator());
- if (!__str._M_is_local()
- && (_Alloc_traits::_S_propagate_on_move_assign()
- || _Alloc_traits::_S_always_equal()))
+ if (__str._M_is_local())
+ {
+ // We've always got room for a short string, just copy it.
+ if (__str.size())
+ this->_S_copy(_M_data(), __str._M_data(), __str.size());
+ _M_set_length(__str.size());
+ }
+ else if (_Alloc_traits::_S_propagate_on_move_assign()
+ || _Alloc_traits::_S_always_equal()
+ || _M_get_allocator() == __str._M_get_allocator())
{
+ // Just move the allocated pointer, our allocator can free it.
pointer __data = nullptr;
size_type __capacity;
if (!_M_is_local())
{
if (_Alloc_traits::_S_always_equal())
{
+ // __str can reuse our existing storage.
__data = _M_data();
__capacity = _M_allocated_capacity;
}
- else
+ else // __str can't use it, so free it.
_M_destroy(_M_allocated_capacity);
}
else
__str._M_data(__str._M_local_buf);
}
- else
- assign(__str);
+ else // Need to do a deep copy
+ assign(__str);
__str.clear();
return *this;
}
--- /dev/null
+// Copyright (C) 2018 Free Software Foundation, Inc.
+//
+// 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
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { target c++11 } }
+
+// PR libstdc++/87749
+
+#include <string>
+#include <testsuite_hooks.h>
+
+bool oom = false;
+
+template<typename T>
+struct alloc
+{
+ using value_type = T;
+
+#if !_GLIBCXX_USE_CXX11_ABI
+ using size_type = unsigned long;
+ using difference_type = long;
+ using reference = T&;
+ using const_reference = T&;
+ using pointer = T*;
+ using const_pointer = const T*;
+ template<typename U>
+ struct rebind { using other = alloc<U>; };
+#endif
+
+ int not_empty = 0; // this makes is_always_equal false
+
+ alloc() = default;
+ template<typename U>
+ alloc(const alloc<U>&) { }
+
+ T* allocate(unsigned long n)
+ {
+ if (oom)
+ throw std::bad_alloc();
+ return std::allocator<T>().allocate(n);
+ }
+
+ void deallocate(T* p, unsigned long n)
+ {
+ std::allocator<T>().deallocate(p, n);
+ }
+};
+
+template<typename T, typename U>
+bool operator==(const alloc<T>&, const alloc<U>&) { return true; }
+
+template<typename T, typename U>
+bool operator!=(const alloc<T>&, const alloc<U>&) { return false; }
+
+int main()
+{
+ using string = std::basic_string<char, std::char_traits<char>, alloc<char>>;
+
+ string s = "PR libstdc++/87749 a string that is longer than a short string";
+ const auto ptr = s.c_str();
+ oom = true;
+ string ss;
+ ss = std::move(s); // allocators are equal, should not allocate new storage
+ VERIFY( ss.c_str() == ptr );
+}
--- /dev/null
+// Copyright (C) 2018 Free Software Foundation, Inc.
+//
+// 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
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-O1" }
+// { dg-do compile { target c++11 } }
+// { dg-final { scan-assembler-not "__throw_length_error" } }
+// { dg-final { scan-assembler-not "__throw_bad_alloc" } }
+
+#include <bits/c++config.h>
+#undef _GLIBCXX_EXTERN_TEMPLATE
+#include <string>
+
+void
+test01(std::string& target, std::string&& source)
+{
+ // The move assignment operator should be simple enough that the compiler
+ // can see that it never results in a length_error or bad_alloc exception
+ // (which would be turned into std::terminate by the noexcept on the
+ // assignment operator).
+ target = std::move(source);
+}
--- /dev/null
+// Copyright (C) 2018 Free Software Foundation, Inc.
+//
+// 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
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { target c++11 } }
+
+// PR libstdc++/87749
+
+#include <string>
+#include <testsuite_hooks.h>
+
+bool oom = false;
+
+template<typename T>
+struct alloc
+{
+ using value_type = T;
+
+#if !_GLIBCXX_USE_CXX11_ABI
+ using size_type = unsigned long;
+ using difference_type = long;
+ using reference = T&;
+ using const_reference = T&;
+ using pointer = T*;
+ using const_pointer = const T*;
+ template<typename U>
+ struct rebind { using other = alloc<U>; };
+#endif
+
+ int not_empty = 0; // this makes is_always_equal false
+
+ alloc() = default;
+ template<typename U>
+ alloc(const alloc<U>&) { }
+
+ T* allocate(unsigned long n)
+ {
+ if (oom)
+ throw std::bad_alloc();
+ return std::allocator<T>().allocate(n);
+ }
+
+ void deallocate(T* p, unsigned long n)
+ {
+ std::allocator<T>().deallocate(p, n);
+ }
+};
+
+template<typename T, typename U>
+bool operator==(const alloc<T>&, const alloc<U>&) { return true; }
+
+template<typename T, typename U>
+bool operator!=(const alloc<T>&, const alloc<U>&) { return false; }
+
+int main()
+{
+ using string
+ = std::basic_string<wchar_t, std::char_traits<wchar_t>, alloc<wchar_t>>;
+
+ string s = L"PR libstdc++/87749 a string that is longer than a short string";
+ const auto ptr = s.c_str();
+ oom = true;
+ string ss;
+ ss = std::move(s); // allocators are equal, should not allocate new storage
+ VERIFY( ss.c_str() == ptr );
+}
--- /dev/null
+// Copyright (C) 2018 Free Software Foundation, Inc.
+//
+// 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
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-O1" }
+// { dg-do compile { target c++11 } }
+// { dg-final { scan-assembler-not "__throw_length_error" } }
+// { dg-final { scan-assembler-not "__throw_bad_alloc" } }
+
+#include <bits/c++config.h>
+#undef _GLIBCXX_EXTERN_TEMPLATE
+#include <string>
+
+void
+test01(std::wstring& target, std::wstring&& source)
+{
+ // The move assignment operator should be simple enough that the compiler
+ // can see that it never results in a length_error or bad_alloc exception
+ // (which would be turned into std::terminate by the noexcept on the
+ // assignment operator).
+ target = std::move(source);
+}
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