From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2153) id 94D433AA940B; Tue, 20 Apr 2021 23:32:47 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 94D433AA940B MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Jakub Jelinek To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r9-9424] libstdc++: Fix up constexpr std::char_traits::compare [PR99181] X-Act-Checkin: gcc X-Git-Author: Jakub Jelinek X-Git-Refname: refs/heads/releases/gcc-9 X-Git-Oldrev: 8a6114146001eafc1921b60e40bf5c0e4f4b8e64 X-Git-Newrev: 03e18a40070c6fe89397a73d85a38a99371cf8a1 Message-Id: <20210420233247.94D433AA940B@sourceware.org> Date: Tue, 20 Apr 2021 23:32:47 +0000 (GMT) X-BeenThere: gcc-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Apr 2021 23:32:47 -0000 https://gcc.gnu.org/g:03e18a40070c6fe89397a73d85a38a99371cf8a1 commit r9-9424-g03e18a40070c6fe89397a73d85a38a99371cf8a1 Author: Jakub Jelinek Date: Tue Feb 23 09:30:18 2021 +0100 libstdc++: Fix up constexpr std::char_traits::compare [PR99181] Because of LWG 467, std::char_traits::lt compares the values cast to unsigned char rather than char, so even when char is signed we get unsigned comparision. std::char_traits::compare uses __builtin_memcmp and that works the same, but during constexpr evaluation we were calling __gnu_cxx::char_traits::compare. As char_traits::lt is not virtual, __gnu_cxx::char_traits::compare used __gnu_cxx::char_traits::lt rather than std::char_traits::lt and thus compared chars as signed if char is signed. This change fixes it by inlining __gnu_cxx::char_traits::compare into std::char_traits::compare by hand, so that it calls the right lt method. 2021-02-23 Jakub Jelinek PR libstdc++/99181 * include/bits/char_traits.h (char_traits::compare): For constexpr evaluation don't call __gnu_cxx::char_traits::compare but do the comparison loop directly. * testsuite/21_strings/char_traits/requirements/char/99181.cc: New test. (cherry picked from commit 311c57f6d8f285d69e44bf94152c753900cb1a0a) Diff: --- libstdc++-v3/include/bits/char_traits.h | 9 ++++- .../char_traits/requirements/char/99181.cc | 40 ++++++++++++++++++++++ 2 files changed, 48 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/bits/char_traits.h b/libstdc++-v3/include/bits/char_traits.h index fd9a3c73930..50bd25eb2df 100644 --- a/libstdc++-v3/include/bits/char_traits.h +++ b/libstdc++-v3/include/bits/char_traits.h @@ -320,7 +320,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION if (__builtin_constant_p(__n) && __constant_char_array_p(__s1, __n) && __constant_char_array_p(__s2, __n)) - return __gnu_cxx::char_traits::compare(__s1, __s2, __n); + { + for (size_t __i = 0; __i < __n; ++__i) + if (lt(__s1[__i], __s2[__i])) + return -1; + else if (lt(__s2[__i], __s1[__i])) + return 1; + return 0; + } #endif return __builtin_memcmp(__s1, __s2, __n); } diff --git a/libstdc++-v3/testsuite/21_strings/char_traits/requirements/char/99181.cc b/libstdc++-v3/testsuite/21_strings/char_traits/requirements/char/99181.cc new file mode 100644 index 00000000000..01a70da046c --- /dev/null +++ b/libstdc++-v3/testsuite/21_strings/char_traits/requirements/char/99181.cc @@ -0,0 +1,40 @@ +// { dg-options "-std=gnu++17" } +// { dg-do run { target c++17 } } + +// Copyright (C) 2021 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 +#include + +void test01() +{ + const char *a = "\x7f"; + const char *b = "\x80"; + int c = std::char_traits::compare(a, b, 2); + constexpr int d = std::char_traits::compare("\x7f", "\x80", 2); + + VERIFY( c && (c < 0) == (static_cast(a[0]) + < static_cast(b[0])) ); + VERIFY( d && (c < 0) == (d < 0) ); +} + +int main() +{ + test01(); + return 0; +}