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[libc++][flat_multimap] Applied [[nodiscard]] #169986

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[libc++][flat_multimap] Applied [[nodiscard]] #169986

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87 changes: 48 additions & 39 deletions libcxx/include/__flat_map/flat_multimap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -408,41 +408,45 @@ class flat_multimap {
}

// iterators
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator begin() noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator begin() noexcept {
return iterator(__containers_.keys.begin(), __containers_.values.begin());
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator begin() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator begin() const noexcept {
return const_iterator(__containers_.keys.begin(), __containers_.values.begin());
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator end() noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator end() noexcept {
return iterator(__containers_.keys.end(), __containers_.values.end());
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator end() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator end() const noexcept {
return const_iterator(__containers_.keys.end(), __containers_.values.end());
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 reverse_iterator rbegin() noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 reverse_iterator rbegin() noexcept {
return reverse_iterator(end());
}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator rbegin() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator rbegin() const noexcept {
return const_reverse_iterator(end());
}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 reverse_iterator rend() noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 reverse_iterator rend() noexcept {
return reverse_iterator(begin());
}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator rend() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator rend() const noexcept {
return const_reverse_iterator(begin());
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator cbegin() const noexcept { return begin(); }
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator cend() const noexcept { return end(); }
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator crbegin() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator cbegin() const noexcept {
return begin();
}
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator cend() const noexcept {
return end();
}
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator crbegin() const noexcept {
return const_reverse_iterator(end());
}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator crend() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator crend() const noexcept {
return const_reverse_iterator(begin());
}

Expand All @@ -451,11 +455,11 @@ class flat_multimap {
return __containers_.keys.empty();
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type size() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type size() const noexcept {
return __containers_.keys.size();
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type max_size() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type max_size() const noexcept {
return std::min<size_type>(__containers_.keys.max_size(), __containers_.values.max_size());
}

Expand Down Expand Up @@ -578,7 +582,7 @@ class flat_multimap {
insert(sorted_equivalent, __il.begin(), __il.end());
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 containers extract() && {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 containers extract() && {
auto __guard = std::__make_scope_guard([&]() noexcept { clear() /* noexcept */; });
auto __ret = std::move(__containers_);
return __ret;
Expand Down Expand Up @@ -644,118 +648,123 @@ class flat_multimap {
}

// observers
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 key_compare key_comp() const { return __compare_; }
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 value_compare value_comp() const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 key_compare key_comp() const { return __compare_; }
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 value_compare value_comp() const {
return value_compare(__compare_);
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const key_container_type& keys() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const key_container_type& keys() const noexcept {
return __containers_.keys;
}
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const mapped_container_type& values() const noexcept {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const mapped_container_type&
values() const noexcept {
return __containers_.values;
}

// map operations
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator find(const key_type& __x) {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator find(const key_type& __x) {
return __find_impl(*this, __x);
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator find(const key_type& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator find(const key_type& __x) const {
return __find_impl(*this, __x);
}

template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator find(const _Kp& __x) {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator find(const _Kp& __x) {
return __find_impl(*this, __x);
}

template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator find(const _Kp& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator find(const _Kp& __x) const {
return __find_impl(*this, __x);
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type count(const key_type& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type count(const key_type& __x) const {
auto [__first, __last] = equal_range(__x);
return __last - __first;
}

template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type count(const _Kp& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type count(const _Kp& __x) const {
auto [__first, __last] = equal_range(__x);
return __last - __first;
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 bool contains(const key_type& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 bool contains(const key_type& __x) const {
return find(__x) != end();
}

template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 bool contains(const _Kp& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 bool contains(const _Kp& __x) const {
return find(__x) != end();
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator lower_bound(const key_type& __x) {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator lower_bound(const key_type& __x) {
return __lower_bound<iterator>(*this, __x);
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator lower_bound(const key_type& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator
lower_bound(const key_type& __x) const {
return __lower_bound<const_iterator>(*this, __x);
}

template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator lower_bound(const _Kp& __x) {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator lower_bound(const _Kp& __x) {
return __lower_bound<iterator>(*this, __x);
}

template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator lower_bound(const _Kp& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator lower_bound(const _Kp& __x) const {
return __lower_bound<const_iterator>(*this, __x);
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator upper_bound(const key_type& __x) {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator upper_bound(const key_type& __x) {
return __upper_bound<iterator>(*this, __x);
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator upper_bound(const key_type& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator
upper_bound(const key_type& __x) const {
return __upper_bound<const_iterator>(*this, __x);
}

template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator upper_bound(const _Kp& __x) {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator upper_bound(const _Kp& __x) {
return __upper_bound<iterator>(*this, __x);
}

template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator upper_bound(const _Kp& __x) const {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator upper_bound(const _Kp& __x) const {
return __upper_bound<const_iterator>(*this, __x);
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<iterator, iterator> equal_range(const key_type& __x) {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<iterator, iterator>
equal_range(const key_type& __x) {
return __equal_range_impl(*this, __x);
}

_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<const_iterator, const_iterator>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<const_iterator, const_iterator>
equal_range(const key_type& __x) const {
return __equal_range_impl(*this, __x);
}

template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<iterator, iterator> equal_range(const _Kp& __x) {
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<iterator, iterator>
equal_range(const _Kp& __x) {
return __equal_range_impl(*this, __x);
}
template <class _Kp>
requires __is_compare_transparent
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<const_iterator, const_iterator>
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<const_iterator, const_iterator>
equal_range(const _Kp& __x) const {
return __equal_range_impl(*this, __x);
}
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@huixie90 huixie90 Nov 30, 2025

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is there a reason why operator== and <=> are not marked?

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@Zingam Zingam Nov 30, 2025

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The compiler is already issuing a diagnostic, so we decided not to mark the operators.

Expand Down
94 changes: 87 additions & 7 deletions libcxx/test/libcxx/diagnostics/flat_multimap.nodiscard.verify.cpp
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,17 +6,97 @@
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
// REQUIRES: std-at-least-c++23

// <flat_map>

// class flat_multimap

// [[nodiscard]] bool empty() const noexcept;
// Check that functions are marked [[nodiscard]]

#include <flat_map>
#include <utility>

template <typename T>
struct TransparentKey {
T t;

constexpr explicit operator T() const { return t; }
};

struct TransparentCompare {
using is_transparent = void; // This makes the comparator transparent

template <typename T>
constexpr bool operator()(const T& t, const TransparentKey<T>& transparent) const {
return t < transparent.t;
}

template <typename T>
constexpr bool operator()(const TransparentKey<T>& transparent, const T& t) const {
return transparent.t < t;
}

template <typename T>
constexpr bool operator()(const T& t1, const T& t2) const {
return t1 < t2;
}
};

void test() {
std::flat_multimap<int, int, TransparentCompare> mm;
const std::flat_multimap<int, int, TransparentCompare> cmm;

mm.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

mm.rbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.rbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.rend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.rend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

cmm.cbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.cend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.crbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.crend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

mm.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

mm.key_comp(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.value_comp(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.keys(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.values(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

int key = 0;
TransparentKey<int> tkey;

mm.find(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.find(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.find(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.find(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

mm.count(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.count(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

mm.contains(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.contains(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.contains(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.contains(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

mm.lower_bound(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.lower_bound(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.lower_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.lower_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

mm.upper_bound(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.upper_bound(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.upper_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.upper_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}

void f() {
std::flat_multimap<int, int> c;
c.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.equal_range(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.equal_range(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
mm.equal_range(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
cmm.equal_range(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
}
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