From 75babad889e3f67c79920bd767111f52d3cdef3c Mon Sep 17 00:00:00 2001 From: Hristo Hristov Date: Wed, 10 Dec 2025 13:59:56 +0200 Subject: [PATCH 1/2] [libc++][multimap] Applied `[[nodiscard]]` `[[nodiscard]]` should be applied to functions where discarding the return value is most likely a correctness issue. - https://libcxx.llvm.org/CodingGuidelines.html --- libcxx/include/map | 92 ++++++++------- .../diagnostics/multimap.nodiscard.verify.cpp | 109 ++++++++++++++++++ 2 files changed, 162 insertions(+), 39 deletions(-) create mode 100644 libcxx/test/libcxx/diagnostics/multimap.nodiscard.verify.cpp diff --git a/libcxx/include/map b/libcxx/include/map index 0dca11cabd12e..3d2b863b70823 100644 --- a/libcxx/include/map +++ b/libcxx/include/map @@ -1703,28 +1703,36 @@ public: static_assert(sizeof(std::__diagnose_non_const_comparator<_Key, _Compare>()), ""); } - _LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT { return __tree_.begin(); } - _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT { return __tree_.begin(); } - _LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT { return __tree_.end(); } - _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT { return __tree_.end(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT { return __tree_.begin(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT { return __tree_.begin(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT { return __tree_.end(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT { return __tree_.end(); } - _LIBCPP_HIDE_FROM_ABI reverse_iterator rbegin() _NOEXCEPT { return reverse_iterator(end()); } - _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rbegin() const _NOEXCEPT { return const_reverse_iterator(end()); } - _LIBCPP_HIDE_FROM_ABI reverse_iterator rend() _NOEXCEPT { return reverse_iterator(begin()); } - _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rend() const _NOEXCEPT { return const_reverse_iterator(begin()); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI reverse_iterator rbegin() _NOEXCEPT { return reverse_iterator(end()); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rbegin() const _NOEXCEPT { + return const_reverse_iterator(end()); + } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI reverse_iterator rend() _NOEXCEPT { return reverse_iterator(begin()); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_reverse_iterator rend() const _NOEXCEPT { + return const_reverse_iterator(begin()); + } - _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT { return begin(); } - _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT { return end(); } - _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crbegin() const _NOEXCEPT { return rbegin(); } - _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crend() const _NOEXCEPT { return rend(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT { return begin(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT { return end(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crbegin() const _NOEXCEPT { return rbegin(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_reverse_iterator crend() const _NOEXCEPT { return rend(); } [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool empty() const _NOEXCEPT { return __tree_.size() == 0; } - _LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT { return __tree_.size(); } - _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT { return __tree_.max_size(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT { return __tree_.size(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT { return __tree_.max_size(); } - _LIBCPP_HIDE_FROM_ABI allocator_type get_allocator() const _NOEXCEPT { return allocator_type(__tree_.__alloc()); } - _LIBCPP_HIDE_FROM_ABI key_compare key_comp() const { return __tree_.value_comp().key_comp(); } - _LIBCPP_HIDE_FROM_ABI value_compare value_comp() const { return value_compare(__tree_.value_comp().key_comp()); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI allocator_type get_allocator() const _NOEXCEPT { + return allocator_type(__tree_.__alloc()); + } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI key_compare key_comp() const { return __tree_.value_comp().key_comp(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI value_compare value_comp() const { + return value_compare(__tree_.value_comp().key_comp()); + } # ifndef _LIBCPP_CXX03_LANG @@ -1794,10 +1802,10 @@ public: "node_type with incompatible allocator passed to multimap::insert()"); return __tree_.template __node_handle_insert_multi(__hint.__i_, std::move(__nh)); } - _LIBCPP_HIDE_FROM_ABI node_type extract(key_type const& __key) { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI node_type extract(key_type const& __key) { return __tree_.template __node_handle_extract(__key); } - _LIBCPP_HIDE_FROM_ABI node_type extract(const_iterator __it) { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI node_type extract(const_iterator __it) { return __tree_.template __node_handle_extract(__it.__i_); } template @@ -1832,83 +1840,89 @@ public: __tree_.swap(__m.__tree_); } - _LIBCPP_HIDE_FROM_ABI iterator find(const key_type& __k) { return __tree_.find(__k); } - _LIBCPP_HIDE_FROM_ABI const_iterator find(const key_type& __k) const { return __tree_.find(__k); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator find(const key_type& __k) { return __tree_.find(__k); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator find(const key_type& __k) const { return __tree_.find(__k); } # if _LIBCPP_STD_VER >= 14 template , int> = 0> - _LIBCPP_HIDE_FROM_ABI iterator find(const _K2& __k) { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator find(const _K2& __k) { return __tree_.find(__k); } template , int> = 0> - _LIBCPP_HIDE_FROM_ABI const_iterator find(const _K2& __k) const { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator find(const _K2& __k) const { return __tree_.find(__k); } # endif - _LIBCPP_HIDE_FROM_ABI size_type count(const key_type& __k) const { return __tree_.__count_multi(__k); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type count(const key_type& __k) const { + return __tree_.__count_multi(__k); + } # if _LIBCPP_STD_VER >= 14 template , int> = 0> - _LIBCPP_HIDE_FROM_ABI size_type count(const _K2& __k) const { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type count(const _K2& __k) const { return __tree_.__count_multi(__k); } # endif # if _LIBCPP_STD_VER >= 20 - _LIBCPP_HIDE_FROM_ABI bool contains(const key_type& __k) const { return find(__k) != end(); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool contains(const key_type& __k) const { return find(__k) != end(); } template , int> = 0> - _LIBCPP_HIDE_FROM_ABI bool contains(const _K2& __k) const { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool contains(const _K2& __k) const { return find(__k) != end(); } # endif // _LIBCPP_STD_VER >= 20 - _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const key_type& __k) { return __tree_.__lower_bound_multi(__k); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const key_type& __k) { + return __tree_.__lower_bound_multi(__k); + } - _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const key_type& __k) const { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const key_type& __k) const { return __tree_.__lower_bound_multi(__k); } # if _LIBCPP_STD_VER >= 14 template , int> = 0> - _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const _K2& __k) { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator lower_bound(const _K2& __k) { return __tree_.__lower_bound_multi(__k); } template , int> = 0> - _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const _K2& __k) const { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator lower_bound(const _K2& __k) const { return __tree_.__lower_bound_multi(__k); } # endif - _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const key_type& __k) { return __tree_.__upper_bound_multi(__k); } + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const key_type& __k) { + return __tree_.__upper_bound_multi(__k); + } - _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const key_type& __k) const { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const key_type& __k) const { return __tree_.__upper_bound_multi(__k); } # if _LIBCPP_STD_VER >= 14 template , int> = 0> - _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const _K2& __k) { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator upper_bound(const _K2& __k) { return __tree_.__upper_bound_multi(__k); } template , int> = 0> - _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const _K2& __k) const { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator upper_bound(const _K2& __k) const { return __tree_.__upper_bound_multi(__k); } # endif - _LIBCPP_HIDE_FROM_ABI pair equal_range(const key_type& __k) { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair equal_range(const key_type& __k) { return __tree_.__equal_range_multi(__k); } - _LIBCPP_HIDE_FROM_ABI pair equal_range(const key_type& __k) const { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair equal_range(const key_type& __k) const { return __tree_.__equal_range_multi(__k); } # if _LIBCPP_STD_VER >= 14 template , int> = 0> - _LIBCPP_HIDE_FROM_ABI pair equal_range(const _K2& __k) { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair equal_range(const _K2& __k) { return __tree_.__equal_range_multi(__k); } template , int> = 0> - _LIBCPP_HIDE_FROM_ABI pair equal_range(const _K2& __k) const { + [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair equal_range(const _K2& __k) const { return __tree_.__equal_range_multi(__k); } # endif diff --git a/libcxx/test/libcxx/diagnostics/multimap.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/multimap.nodiscard.verify.cpp new file mode 100644 index 0000000000000..7ac36e02cc9f7 --- /dev/null +++ b/libcxx/test/libcxx/diagnostics/multimap.nodiscard.verify.cpp @@ -0,0 +1,109 @@ +//===----------------------------------------------------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +// Check that functions are marked [[nodiscard]] + +#include +#include +#include + +#include "test_macros.h" + +#if TEST_STD_VER >= 14 +struct TransparentKey { + explicit operator int() const; +}; + +struct TransparentCompare { + using is_transparent = void; // This makes the comparator transparent + + bool operator()(const int&, const TransparentKey&) const; + + bool operator()(const TransparentKey&, const int&) const; + + bool operator()(const int&, const int&) const; +}; +#endif // TEST_STD_VER >= 14 + +void test() { + std::multimap m; + const std::multimap cm; + + m.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + m.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + m.rbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.rbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + m.rend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.rend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + cm.cbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.cend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.crbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.crend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + m.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + m.size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + m.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + m.get_allocator(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + m.key_comp(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + m.value_comp(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + + int key = 0; + +#if TEST_STD_VER >= 17 + m.extract(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + m.extract(m.cend()); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif + + m.find(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.find(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#if TEST_STD_VER >= 14 + std::map tm; + const std::map ctm{}; + + TransparentKey tkey; + + tm.find(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + ctm.find(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif + + m.count(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#if TEST_STD_VER >= 14 + tm.count(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif + +#if TEST_STD_VER >= 20 + m.contains(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + tm.contains(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif + + m.lower_bound(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.lower_bound(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#if TEST_STD_VER >= 14 + tm.lower_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + ctm.lower_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif + + m.upper_bound(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.upper_bound(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#if TEST_STD_VER >= 14 + tm.upper_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + ctm.upper_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif + + m.equal_range(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + cm.equal_range(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#if TEST_STD_VER >= 14 + tm.equal_range(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} + ctm.equal_range(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} +#endif +} From deaf1cb8283d265de882ae6c38b55d5c1e4692d1 Mon Sep 17 00:00:00 2001 From: Hristo Hristov Date: Wed, 10 Dec 2025 18:44:42 +0200 Subject: [PATCH 2/2] [libc++][multimap] Applied `[[nodiscard]]` `[[nodiscard]]` should be applied to functions where discarding the return value is most likely a correctness issue. - https://libcxx.llvm.org/CodingGuidelines.html --- libcxx/test/libcxx/diagnostics/multimap.nodiscard.verify.cpp | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/libcxx/test/libcxx/diagnostics/multimap.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/multimap.nodiscard.verify.cpp index 7ac36e02cc9f7..99e4fbceabf12 100644 --- a/libcxx/test/libcxx/diagnostics/multimap.nodiscard.verify.cpp +++ b/libcxx/test/libcxx/diagnostics/multimap.nodiscard.verify.cpp @@ -67,8 +67,8 @@ void test() { m.find(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} cm.find(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}} #if TEST_STD_VER >= 14 - std::map tm; - const std::map ctm{}; + std::multimap tm; + const std::multimap ctm{}; TransparentKey tkey;