public inbox for libstdc++-cvs@sourceware.org help / color / mirror / Atom feed
From: Michael Meissner <meissner@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc(refs/users/meissner/heads/work013)] libstdc++: Constrain chrono::duration conversions [LWG 2094] Date: Tue, 1 Sep 2020 20:27:08 +0000 (GMT) [thread overview] Message-ID: <20200901202708.E9E9D3870890@sourceware.org> (raw) https://gcc.gnu.org/g:b1850c617b14eedaf60b358f3b7d4707cff73b8a commit b1850c617b14eedaf60b358f3b7d4707cff73b8a Author: Jonathan Wakely <jwakely@redhat.com> Date: Tue Sep 1 18:18:26 2020 +0100 libstdc++: Constrain chrono::duration conversions [LWG 2094] The chrono::duration constructor that converts from another duration type is meant to be constrained so that it doesn't participate in overload resolution if the ratio of the periods cannot be represented as a std::ratio. Because our std::ratio_divide is not SFINAE-friendly the evaluation of __is_harmonic results in an error outside the immediate context when an overflow occurs. I intend to make ratio_divide (and ratio_multiply) SFINAE-friendly in a future patch, but for now this patch just introduces a new SFINAE-friendly alias template for the division. The standard doesn't require it, but it also seems right to constrain the constructor with std::is_convertible_v<_Rep2, rep>. libstdc++-v3/ChangeLog: * include/std/chrono (duration::_S_gcd(intmax_t, intmax_t)): New helper function for finding GCD of two positive intmax_t values. (duration::__divide): New helper alias for dividing one period by another. (duration::__is_harmonic): Use __divide not ratio_divide. (duration(const duration<R2, P2>&)): Require the duration rep types to be convertible. * testsuite/20_util/duration/cons/dr2094.cc: New test. * testsuite/20_util/duration/requirements/reduced_period.cc: Fix definition of unused member functions in test type. * testsuite/20_util/duration/requirements/typedefs_neg2.cc: Adjust expected errors. Diff: --- libstdc++-v3/include/std/chrono | 21 ++++++- .../testsuite/20_util/duration/cons/dr2094.cc | 64 ++++++++++++++++++++++ .../duration/requirements/reduced_period.cc | 10 ++-- .../20_util/duration/requirements/typedefs_neg2.cc | 1 + 4 files changed, 90 insertions(+), 6 deletions(-) diff --git a/libstdc++-v3/include/std/chrono b/libstdc++-v3/include/std/chrono index 524d23ea6a7..1682263fd9f 100644 --- a/libstdc++-v3/include/std/chrono +++ b/libstdc++-v3/include/std/chrono @@ -424,10 +424,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Rep2> using __is_float = treat_as_floating_point<_Rep2>; + static constexpr intmax_t + _S_gcd(intmax_t __m, intmax_t __n) noexcept + { + // Duration only allows positive periods so we don't need to + // support negative values here (unlike __static_gcd and std::gcd). + return (__m == 0) ? __n : (__n == 0) ? __m : _S_gcd(__n, __m % __n); + } + + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 2094. overflow shouldn't participate in overload resolution + // 3090. What is [2094] intended to mean? + // This only produces a valid type if no overflow occurs. + template<typename _R1, typename _R2, + intmax_t __gcd1 = _S_gcd(_R1::num, _R2::num), + intmax_t __gcd2 = _S_gcd(_R1::den, _R2::den)> + using __divide = ratio<(_R1::num / __gcd1) * (_R2::den / __gcd2), + (_R1::den / __gcd2) * (_R2::num / __gcd1)>; + // _Period2 is an exact multiple of _Period template<typename _Period2> using __is_harmonic - = __bool_constant<ratio_divide<_Period2, _Period>::den == 1>; + = __bool_constant<__divide<_Period2, _Period>::den == 1>; public: @@ -453,6 +471,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION : __r(static_cast<rep>(__rep)) { } template<typename _Rep2, typename _Period2, typename = _Require< + is_convertible<const _Rep2&, rep>, __or_<__is_float<rep>, __and_<__is_harmonic<_Period2>, __not_<__is_float<_Rep2>>>>>> diff --git a/libstdc++-v3/testsuite/20_util/duration/cons/dr2094.cc b/libstdc++-v3/testsuite/20_util/duration/cons/dr2094.cc new file mode 100644 index 00000000000..859c14fe693 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/duration/cons/dr2094.cc @@ -0,0 +1,64 @@ +// Copyright (C) 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 +// <http://www.gnu.org/licenses/>. + +// { dg-do compile { target c++11 } } + +#include <chrono> + +void +test01() +{ + using namespace std::chrono; + using std::exa; + + // LWG 2094 + // duration conversion overflow shouldn't participate in overload resolution + bool f(milliseconds); + void f(seconds); + duration<int,exa> r(1); + f(r); +} + +void +test02() +{ + struct Number + { + explicit + Number(int t = 0) : i(t) + { } + + int i = 0; + + Number& operator+=(Number n) { i += n.i; return *this; } + Number& operator-=(Number n) { i -= n.i; return *this; } + Number& operator*=(Number n) { i *= n.i; return *this; } + Number& operator/=(Number n) { i /= n.i; return *this; } + Number& operator%=(Number n) { i %= n.i; return *this; } + + Number operator+(Number n) { return Number{ i + n.i }; } + Number operator-(Number n) { return Number{ i - n.i }; } + Number operator*(Number n) { return Number{ i * n.i }; } + Number operator/(Number n) { return Number{ i / n.i }; } + Number operator%(Number n) { return Number{ i % n.i }; } + }; + + using std::chrono::duration; + + static_assert( ! std::is_constructible<duration<int>, duration<Number>>(), + "duration(const duration<R2, P2>&) constrained on R2 -> R conversion" ); +} diff --git a/libstdc++-v3/testsuite/20_util/duration/requirements/reduced_period.cc b/libstdc++-v3/testsuite/20_util/duration/requirements/reduced_period.cc index 4c7472699d2..87124e526b3 100644 --- a/libstdc++-v3/testsuite/20_util/duration/requirements/reduced_period.cc +++ b/libstdc++-v3/testsuite/20_util/duration/requirements/reduced_period.cc @@ -151,11 +151,11 @@ struct Number Number& operator/=(Number n) { i /= n.i; return *this; } Number& operator%=(Number n) { i %= n.i; return *this; } - Number operator+(Number n) { return { i + n.i }; } - Number operator-(Number n) { return { i - n.i }; } - Number operator*(Number n) { return { i * n.i }; } - Number operator/(Number n) { return { i / n.i }; } - Number operator%(Number n) { return { i % n.i }; } + Number operator+(Number n) { return Number{ i + n.i }; } + Number operator-(Number n) { return Number{ i - n.i }; } + Number operator*(Number n) { return Number{ i * n.i }; } + Number operator/(Number n) { return Number{ i / n.i }; } + Number operator%(Number n) { return Number{ i % n.i }; } }; namespace std diff --git a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc index 02dab73b0eb..e44b01c4c82 100644 --- a/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc +++ b/libstdc++-v3/testsuite/20_util/duration/requirements/typedefs_neg2.cc @@ -32,4 +32,5 @@ void test01() // { dg-error "must be a specialization of ratio" "" { target *-*-* } 0 } // { dg-prune-output "'num' is not a member of 'int'" } +// { dg-prune-output "'den' is not a member of 'int'" } // { dg-prune-output "'int' is not a class, struct, or union type" }
reply other threads:[~2020-09-01 20:27 UTC|newest] Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20200901202708.E9E9D3870890@sourceware.org \ --to=meissner@gcc.gnu.org \ --cc=gcc-cvs@gcc.gnu.org \ --cc=libstdc++-cvs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).