LWG2788 basic_string spurious use of a default constructible allocator

This only change the cxx11 basic_string, because COW strings don't
correctly propagate allocators anyway.

2019-05-30  Nina Dinka Ranns  <dinka.ranns@gmail.com>

	LWG2788 basic_string spurious use of a default constructible allocator
	* include/bits/basic_string.tcc [_GLIBCXX_USE_CXX11_ABI]
	(basic_string::_M_replace_dispatch): Construct temporary string with
	the current allocator.
	* testsuite/21_strings/basic_string/allocator/char/lwg2788.cc: New.
	* testsuite/21_strings/basic_string/allocator/wchar_t/lwg2788.cc: New.

From-SVN: r271789

2 files changed, 170 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/lwg2788.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/lwg2788.cc
new file mode 100644
index 00000000000..36dd414e887
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/char/lwg2788.cc
@@ -0,0 +1,85 @@
+// { dg-do run { target c++11 } }
+// { dg-require-effective-target cxx11-abi }
+
+// 2019-05-27  Nina Dinka Ranns  <dinka.ranns@gmail.com>
+//
+// Copyright (C) 2015-2019 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/>.
+
+#include <string>
+#include <testsuite_hooks.h>
+
+using C = char;
+using traits = std::char_traits<C>;
+int constructCount = 0;
+
+static void resetCounter()
+{
+ constructCount = 0;
+}
+
+template <class Tp>
+struct TestAllocator
+{
+  typedef Tp value_type;
+  using size_type = unsigned;
+
+  TestAllocator() noexcept { constructCount++; }
+
+  template <class T>
+  TestAllocator(const TestAllocator<T>&) {}
+
+  Tp *allocate(std::size_t n)
+  { return std::allocator<Tp>().allocate(n); }
+
+  void deallocate(Tp *p, std::size_t n)
+  { std::allocator<Tp>().deallocate(p, n); }
+
+};
+
+template <class T, class U>
+bool operator==(const TestAllocator<T>&, const TestAllocator<U>&)
+{ return true; }
+template <class T, class U>
+bool operator!=(const TestAllocator<T>&, const TestAllocator<U>&)
+{ return false; }
+
+void test01()
+{
+  typedef TestAllocator<C> alloc_type;
+  typedef std::basic_string<C, traits, alloc_type> test_type;
+  test_type v1{alloc_type()};
+  std::string v2{"some_content"};
+
+  resetCounter();
+  v1.assign(v2.begin(),v2.end());
+  VERIFY( constructCount == 0);
+
+  v1.append(v2.begin(),v2.end());
+  VERIFY( constructCount == 0);
+
+  v1.insert(v1.begin(),v1.begin(),v1.end());
+  VERIFY( constructCount == 0);
+
+  v1.replace(v1.begin(),v1.end(),v1.begin(),v1.end());
+  VERIFY( constructCount == 0);
+}
+int main()
+{
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/lwg2788.cc b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/lwg2788.cc
new file mode 100644
index 00000000000..8e26dd7d4a9
--- /dev/null
+++ b/libstdc++-v3/testsuite/21_strings/basic_string/allocator/wchar_t/lwg2788.cc
@@ -0,0 +1,85 @@
+// { dg-do run { target c++11 } }
+// { dg-require-effective-target cxx11-abi }
+
+// 2019-05-27  Nina Dinka Ranns  <dinka.ranns@gmail.com>
+//
+// Copyright (C) 2015-2019 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/>.
+
+#include <string>
+#include <testsuite_hooks.h>
+
+using C = wchar_t;
+using traits = std::char_traits<C>;
+int constructCount = 0;
+
+static void resetCounter()
+{
+ constructCount = 0;
+}
+
+template <class Tp>
+struct TestAllocator
+{
+  typedef Tp value_type;
+  using size_type = unsigned;
+
+  TestAllocator() noexcept { constructCount++; }
+
+  template <class T>
+  TestAllocator(const TestAllocator<T>&) {}
+
+  Tp *allocate(std::size_t n)
+  { return std::allocator<Tp>().allocate(n); }
+
+  void deallocate(Tp *p, std::size_t n)
+  { std::allocator<Tp>().deallocate(p, n); }
+
+};
+
+template <class T, class U>
+bool operator==(const TestAllocator<T>&, const TestAllocator<U>&)
+{ return true; }
+template <class T, class U>
+bool operator!=(const TestAllocator<T>&, const TestAllocator<U>&)
+{ return false; }
+
+void test01()
+{
+  typedef TestAllocator<C> alloc_type;
+  typedef std::basic_string<C, traits, alloc_type> test_type;
+  test_type v1{alloc_type()};
+  std::wstring v2{L"some_content"};
+
+  resetCounter();
+  v1.assign(v2.begin(),v2.end());
+  VERIFY( constructCount == 0);
+
+  v1.append(v2.begin(),v2.end());
+  VERIFY( constructCount == 0);
+
+  v1.insert(v1.begin(),v1.begin(),v1.end());
+  VERIFY( constructCount == 0);
+
+  v1.replace(v1.begin(),v1.end(),v1.begin(),v1.end());
+  VERIFY( constructCount == 0);
+}
+int main()
+{
+  test01();
+  return 0;
+}