[libc++][multimap] Applied [[nodiscard]]
#171644
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`[[nodiscard]]` should be applied to functions where discarding the return value is most likely a correctness issue. - https://libcxx.llvm.org/CodingGuidelines.html
`[[nodiscard]]` should be applied to functions where discarding the return value is most likely a correctness issue. - https://libcxx.llvm.org/CodingGuidelines.html
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@llvm/pr-subscribers-libcxx Author: Hristo Hristov (H-G-Hristov) Changes
Full diff: https://github.com/llvm/llvm-project/pull/171644.diff 2 Files Affected:
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<node_type>(__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<node_type>(__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<node_type>(__it.__i_);
}
template <class _Compare2>
@@ -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 <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, 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 <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, 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 <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, 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 <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, 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 <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, 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 <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, 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 <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, 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 <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, 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<iterator, iterator> equal_range(const key_type& __k) {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const key_type& __k) {
return __tree_.__equal_range_multi(__k);
}
- _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const key_type& __k) const {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const key_type& __k) const {
return __tree_.__equal_range_multi(__k);
}
# if _LIBCPP_STD_VER >= 14
template <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, int> = 0>
- _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const _K2& __k) {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const _K2& __k) {
return __tree_.__equal_range_multi(__k);
}
template <typename _K2, enable_if_t<__is_transparent_v<_Compare, _K2>, int> = 0>
- _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const _K2& __k) const {
+ [[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> 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..99e4fbceabf12
--- /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 <map>
+#include <string>
+#include <utility>
+
+#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<int, int> m;
+ const std::multimap<int, int> 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::multimap<int, int, TransparentCompare> tm;
+ const std::multimap<int, int, TransparentCompare> 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
+}
|
Contributor
|
Mostly LGTM, but CI failure looked quite weird to me. I think we can update the branch to see what's still failing. |
Contributor
This is a recurring issue with macOS CI since yesterday I think. I restarted the stuck jobs, which should be quicker. If that fails I'll rebase. |
Contributor
|
It also looks that the GitHub UI doesn't update the status correctly, e.g. this one isn't "in progress" and there is no "Approved" label on those that are approved, even filtering them out doesn't seem to work correctly. |
84 tasks
Contributor
Restarting the CI job did make it pass. |
frederick-vs-ja
approved these changes
Dec 15, 2025
anonymouspc
pushed a commit
to anonymouspc/llvm
that referenced
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Dec 15, 2025
`[[nodiscard]]` should be applied to functions where discarding the return value is most likely a correctness issue. - https://libcxx.llvm.org/CodingGuidelines.html - https://wg21.link/multimap
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[[nodiscard]]should be applied to functions where discarding the return value is most likely a correctness issue.