From eb11134d0c4e4db623aefe433c9613632ef8618e Mon Sep 17 00:00:00 2001 From: Paul Keir Date: Mon, 15 Jun 2020 14:31:26 +0100 Subject: [PATCH] libstdc++: Fix char_traits move with overlap Upon constexpr evaluation, char_traits move uses copy_backward, but its last argument should be to the range end rather than its beginning. 2020-06-12 Paul Keir * include/bits/char_traits.h (char_traits::move): constexpr move with overlap was using copy_backward incorrectly. * testsuite/21_strings/char_traits/requirements/constexpr_functions_c++20.cc: New test. --- libstdc++-v3/include/bits/char_traits.h | 2 +- .../requirements/constexpr_functions_c++20.cc | 52 ++++++++++++++++++++++ 2 files changed, 53 insertions(+), 1 deletion(-) create mode 100644 libstdc++-v3/testsuite/21_strings/char_traits/requirements/constexpr_functions_c++20.cc diff --git a/libstdc++-v3/include/bits/char_traits.h b/libstdc++-v3/include/bits/char_traits.h index c6da184..c623a67 100644 --- a/libstdc++-v3/include/bits/char_traits.h +++ b/libstdc++-v3/include/bits/char_traits.h @@ -196,7 +196,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION if (std::is_constant_evaluated()) { if (__s1 > __s2 && __s1 < __s2 + __n) - std::copy_backward(__s2, __s2 + __n, __s1); + std::copy_backward(__s2, __s2 + __n, __s1 + __n); else std::copy(__s2, __s2 + __n, __s1); return __s1; diff --git a/libstdc++-v3/testsuite/21_strings/char_traits/requirements/constexpr_functions_c++20.cc b/libstdc++-v3/testsuite/21_strings/char_traits/requirements/constexpr_functions_c++20.cc new file mode 100644 index 0000000..6358640 --- /dev/null +++ b/libstdc++-v3/testsuite/21_strings/char_traits/requirements/constexpr_functions_c++20.cc @@ -0,0 +1,52 @@ +// { dg-options "-std=gnu++2a" } +// { dg-do compile { target c++2a } } + +// Copyright (C) 2017-2020 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 +// . + +#include + +template + constexpr bool + test_move() + { + using char_type = typename CT::char_type; + char_type s1[3] = {1, 2, 3}; + CT::move(s1+1, s1, 2); + return s1[0]==char_type{1} && s1[1]==char_type{1} && s1[2]==char_type{2}; + } + +#ifndef __cpp_lib_constexpr_char_traits +# error Feature-test macro for constexpr char_traits is missing +#elif __cpp_lib_constexpr_char_traits != 201611 +# error Feature-test macro for constexpr char_traits has the wrong value +#endif + +static_assert( test_move>() ); +#ifdef _GLIBCXX_USE_WCHAR_T +static_assert( test_move>() ); +#endif +#ifdef _GLIBCXX_USE_CHAR8_T +static_assert( test_move>() ); +#endif +static_assert( test_move>() ); +static_assert( test_move>() ); + +struct C { unsigned char c; }; +constexpr bool operator==(const C& c1, const C& c2) { return c1.c == c2.c; } +constexpr bool operator<(const C& c1, const C& c2) { return c1.c < c2.c; } +static_assert( test_move>() ); -- 2.7.4