df483ebd24
Add the [[nodiscard]] attribute to several functions in <algorithm>. These all have no side effects and are only called for their return value (e.g. std::count) or produce a result that must not be discarded for correctness (e.g. std::remove). I was intending to add the attribute to a number of other functions like std::copy_if, std::unique_copy, std::set_union, and std::set_difference. I stopped when I noticed that MSVC doesn't use it on those functions, which I suspect is because they're often used with an insert iterator (e.g. std::back_insert_iterator). In that case it doesn't matter if you discard the result, because you have the container to tell you how many elements were copied to the output range. libstdc++-v3/ChangeLog: * include/bits/stl_algo.h (find_end, all_of, none_of, any_of) (find_if_not, is_partitioned, partition_point, remove) (remove_if, unique, lower_bound, upper_bound, equal_range) (binary_search, includes, is_sorted, is_sorted_until, minmax) (minmax_element, is_permutation, clamp, find_if, find_first_of) (adjacent_find, count, count_if, search, search_n, min_element) (max_element): Add nodiscard attribute. * include/bits/stl_algobase.h (min, max, lower_bound, equal) (lexicographical_compare, lexicographical_compare_three_way) (mismatch): Likewise. * include/bits/stl_heap.h (is_heap, is_heap_until): Likewise. * testsuite/25_algorithms/equal/debug/1_neg.cc: Add dg-warning. * testsuite/25_algorithms/equal/debug/2_neg.cc: Likewise. * testsuite/25_algorithms/equal/debug/3_neg.cc: Likewise. * testsuite/25_algorithms/find_first_of/concept_check_1.cc: Likewise. * testsuite/25_algorithms/is_permutation/2.cc: Likewise. * testsuite/25_algorithms/lexicographical_compare/71545.cc: Likewise. * testsuite/25_algorithms/lower_bound/33613.cc: Likewise. * testsuite/25_algorithms/lower_bound/debug/irreflexive.cc: Likewise. * testsuite/25_algorithms/lower_bound/debug/partitioned_neg.cc: Likewise. * testsuite/25_algorithms/lower_bound/debug/partitioned_pred_neg.cc: Likewise. * testsuite/25_algorithms/minmax/3.cc: Likewise. * testsuite/25_algorithms/search/78346.cc: Likewise. * testsuite/25_algorithms/search_n/58358.cc: Likewise. * testsuite/25_algorithms/unique/1.cc: Likewise. * testsuite/25_algorithms/unique/11480.cc: Likewise. * testsuite/25_algorithms/upper_bound/33613.cc: Likewise. * testsuite/25_algorithms/upper_bound/debug/partitioned_neg.cc: Likewise. * testsuite/25_algorithms/upper_bound/debug/partitioned_pred_neg.cc: Likewise. * testsuite/ext/concept_checks.cc: Likewise. * testsuite/ext/is_heap/47709.cc: Likewise. * testsuite/ext/is_sorted/cxx0x.cc: Likewise.
57 lines
1.5 KiB
C++
57 lines
1.5 KiB
C++
// { dg-do run { target c++11 } }
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// 2008-09-16 Chris Fairles <chris.fairles@gmail.com>
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// Copyright (C) 2008-2024 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License along
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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#include <algorithm>
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#include <functional>
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#include <testsuite_hooks.h>
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struct compare_counter
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{
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typedef int result_type;
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typedef int first_argument_type;
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typedef bool second_argument_type;
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static int count;
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bool operator()(int a, int b) const
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{
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++count;
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return a < b;
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}
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};
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int compare_counter::count = 0;
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void test01()
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{
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std::minmax({1, 2, 3, 4, 5, 6, 7, 8}, compare_counter());
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// { dg-warning "ignoring return value" "" { target c++17 } 45 }
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// If N is the number of arguments in the minmax function call,
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// 25.3.7 specifies that at most 3N/2 comparisons are allowed.
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VERIFY(compare_counter::count <= (3 * 8 / 2));
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}
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int main()
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{
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test01();
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return 0;
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}
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