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H-G-HristovH-G-Hristov
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[libc++][unordered_map] 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 - https://wg21.link/unord.multimap
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3 files changed

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‎libcxx/include/unordered_map‎

Lines changed: 53 additions & 41 deletions
Original file line numberDiff line numberDiff line change
@@ -1034,20 +1034,20 @@ public:
10341034
_LIBCPP_HIDE_FROM_ABI unordered_map& operator=(initializer_list<value_type> __il);
10351035
# endif // _LIBCPP_CXX03_LANG
10361036

1037-
_LIBCPP_HIDE_FROM_ABI allocator_type get_allocator() const _NOEXCEPT {
1037+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI allocator_type get_allocator() const _NOEXCEPT {
10381038
return allocator_type(__table_.__node_alloc());
10391039
}
10401040

10411041
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI bool empty() const _NOEXCEPT { return __table_.size() == 0; }
1042-
_LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT { return __table_.size(); }
1043-
_LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT { return __table_.max_size(); }
1042+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type size() const _NOEXCEPT { return __table_.size(); }
1043+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT { return __table_.max_size(); }
10441044

1045-
_LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT { return __table_.begin(); }
1046-
_LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT { return __table_.end(); }
1047-
_LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT { return __table_.begin(); }
1048-
_LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT { return __table_.end(); }
1049-
_LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT { return __table_.begin(); }
1050-
_LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT { return __table_.end(); }
1045+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT { return __table_.begin(); }
1046+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT { return __table_.end(); }
1047+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT { return __table_.begin(); }
1048+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT { return __table_.end(); }
1049+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT { return __table_.begin(); }
1050+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT { return __table_.end(); }
10511051

10521052
_LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert(const value_type& __x) { return __table_.__emplace_unique(__x); }
10531053

@@ -1171,10 +1171,10 @@ public:
11711171
"node_type with incompatible allocator passed to unordered_map::insert()");
11721172
return __table_.template __node_handle_insert_unique<node_type>(__hint.__i_, std::move(__nh));
11731173
}
1174-
_LIBCPP_HIDE_FROM_ABI node_type extract(key_type const& __key) {
1174+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI node_type extract(key_type const& __key) {
11751175
return __table_.template __node_handle_extract<node_type>(__key);
11761176
}
1177-
_LIBCPP_HIDE_FROM_ABI node_type extract(const_iterator __it) {
1177+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI node_type extract(const_iterator __it) {
11781178
return __table_.template __node_handle_extract<node_type>(__it.__i_);
11791179
}
11801180

@@ -1208,79 +1208,91 @@ public:
12081208
__table_.swap(__u.__table_);
12091209
}
12101210

1211-
_LIBCPP_HIDE_FROM_ABI hasher hash_function() const { return __table_.hash_function().hash_function(); }
1212-
_LIBCPP_HIDE_FROM_ABI key_equal key_eq() const { return __table_.key_eq().key_eq(); }
1211+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI hasher hash_function() const {
1212+
return __table_.hash_function().hash_function();
1213+
}
1214+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI key_equal key_eq() const { return __table_.key_eq().key_eq(); }
12131215

1214-
_LIBCPP_HIDE_FROM_ABI iterator find(const key_type& __k) { return __table_.find(__k); }
1215-
_LIBCPP_HIDE_FROM_ABI const_iterator find(const key_type& __k) const { return __table_.find(__k); }
1216+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI iterator find(const key_type& __k) { return __table_.find(__k); }
1217+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_iterator find(const key_type& __k) const { return __table_.find(__k); }
12161218
# if _LIBCPP_STD_VER >= 20
12171219
template <class _K2, enable_if_t<__is_transparent_v<hasher, _K2> && __is_transparent_v<key_equal, _K2>>* = nullptr>
1218-
_LIBCPP_HIDE_FROM_ABI iterator find(const _K2& __k) {
1220+
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI iterator find(const _K2& __k) {
12191221
return __table_.find(__k);
12201222
}
12211223
template <class _K2, enable_if_t<__is_transparent_v<hasher, _K2> && __is_transparent_v<key_equal, _K2>>* = nullptr>
1222-
_LIBCPP_HIDE_FROM_ABI const_iterator find(const _K2& __k) const {
1224+
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI const_iterator find(const _K2& __k) const {
12231225
return __table_.find(__k);
12241226
}
12251227
# endif // _LIBCPP_STD_VER >= 20
12261228

1227-
_LIBCPP_HIDE_FROM_ABI size_type count(const key_type& __k) const { return __table_.__count_unique(__k); }
1229+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type count(const key_type& __k) const {
1230+
return __table_.__count_unique(__k);
1231+
}
12281232
# if _LIBCPP_STD_VER >= 20
12291233
template <class _K2, enable_if_t<__is_transparent_v<hasher, _K2> && __is_transparent_v<key_equal, _K2>>* = nullptr>
1230-
_LIBCPP_HIDE_FROM_ABI size_type count(const _K2& __k) const {
1234+
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI size_type count(const _K2& __k) const {
12311235
return __table_.__count_unique(__k);
12321236
}
12331237
# endif // _LIBCPP_STD_VER >= 20
12341238

12351239
# if _LIBCPP_STD_VER >= 20
1236-
_LIBCPP_HIDE_FROM_ABI bool contains(const key_type& __k) const { return find(__k) != end(); }
1240+
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool contains(const key_type& __k) const { return find(__k) != end(); }
12371241

12381242
template <class _K2, enable_if_t<__is_transparent_v<hasher, _K2> && __is_transparent_v<key_equal, _K2>>* = nullptr>
1239-
_LIBCPP_HIDE_FROM_ABI bool contains(const _K2& __k) const {
1243+
[[nodiscard]] _LIBCPP_HIDE_FROM_ABI bool contains(const _K2& __k) const {
12401244
return find(__k) != end();
12411245
}
12421246
# endif // _LIBCPP_STD_VER >= 20
12431247

1244-
_LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const key_type& __k) {
1248+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const key_type& __k) {
12451249
return __table_.__equal_range_unique(__k);
12461250
}
1247-
_LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const key_type& __k) const {
1251+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const key_type& __k) const {
12481252
return __table_.__equal_range_unique(__k);
12491253
}
12501254
# if _LIBCPP_STD_VER >= 20
12511255
template <class _K2, enable_if_t<__is_transparent_v<hasher, _K2> && __is_transparent_v<key_equal, _K2>>* = nullptr>
1252-
_LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const _K2& __k) {
1256+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<iterator, iterator> equal_range(const _K2& __k) {
12531257
return __table_.__equal_range_unique(__k);
12541258
}
12551259
template <class _K2, enable_if_t<__is_transparent_v<hasher, _K2> && __is_transparent_v<key_equal, _K2>>* = nullptr>
1256-
_LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const _K2& __k) const {
1260+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI pair<const_iterator, const_iterator> equal_range(const _K2& __k) const {
12571261
return __table_.__equal_range_unique(__k);
12581262
}
12591263
# endif // _LIBCPP_STD_VER >= 20
12601264

1261-
_LIBCPP_HIDE_FROM_ABI mapped_type& operator[](const key_type& __k);
1265+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI mapped_type& operator[](const key_type& __k);
12621266
# ifndef _LIBCPP_CXX03_LANG
1263-
_LIBCPP_HIDE_FROM_ABI mapped_type& operator[](key_type&& __k);
1267+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI mapped_type& operator[](key_type&& __k);
12641268
# endif
12651269

1266-
_LIBCPP_HIDE_FROM_ABI mapped_type& at(const key_type& __k);
1267-
_LIBCPP_HIDE_FROM_ABI const mapped_type& at(const key_type& __k) const;
1270+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI mapped_type& at(const key_type& __k);
1271+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const mapped_type& at(const key_type& __k) const;
12681272

1269-
_LIBCPP_HIDE_FROM_ABI size_type bucket_count() const _NOEXCEPT { return __table_.bucket_count(); }
1270-
_LIBCPP_HIDE_FROM_ABI size_type max_bucket_count() const _NOEXCEPT { return __table_.max_bucket_count(); }
1273+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type bucket_count() const _NOEXCEPT { return __table_.bucket_count(); }
1274+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type max_bucket_count() const _NOEXCEPT {
1275+
return __table_.max_bucket_count();
1276+
}
12711277

1272-
_LIBCPP_HIDE_FROM_ABI size_type bucket_size(size_type __n) const { return __table_.bucket_size(__n); }
1273-
_LIBCPP_HIDE_FROM_ABI size_type bucket(const key_type& __k) const { return __table_.bucket(__k); }
1278+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type bucket_size(size_type __n) const {
1279+
return __table_.bucket_size(__n);
1280+
}
1281+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI size_type bucket(const key_type& __k) const { return __table_.bucket(__k); }
12741282

1275-
_LIBCPP_HIDE_FROM_ABI local_iterator begin(size_type __n) { return __table_.begin(__n); }
1276-
_LIBCPP_HIDE_FROM_ABI local_iterator end(size_type __n) { return __table_.end(__n); }
1277-
_LIBCPP_HIDE_FROM_ABI const_local_iterator begin(size_type __n) const { return __table_.cbegin(__n); }
1278-
_LIBCPP_HIDE_FROM_ABI const_local_iterator end(size_type __n) const { return __table_.cend(__n); }
1279-
_LIBCPP_HIDE_FROM_ABI const_local_iterator cbegin(size_type __n) const { return __table_.cbegin(__n); }
1280-
_LIBCPP_HIDE_FROM_ABI const_local_iterator cend(size_type __n) const { return __table_.cend(__n); }
1283+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI local_iterator begin(size_type __n) { return __table_.begin(__n); }
1284+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI local_iterator end(size_type __n) { return __table_.end(__n); }
1285+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_local_iterator begin(size_type __n) const {
1286+
return __table_.cbegin(__n);
1287+
}
1288+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_local_iterator end(size_type __n) const { return __table_.cend(__n); }
1289+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_local_iterator cbegin(size_type __n) const {
1290+
return __table_.cbegin(__n);
1291+
}
1292+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI const_local_iterator cend(size_type __n) const { return __table_.cend(__n); }
12811293

1282-
_LIBCPP_HIDE_FROM_ABI float load_factor() const _NOEXCEPT { return __table_.load_factor(); }
1283-
_LIBCPP_HIDE_FROM_ABI float max_load_factor() const _NOEXCEPT { return __table_.max_load_factor(); }
1294+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI float load_factor() const _NOEXCEPT { return __table_.load_factor(); }
1295+
[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI float max_load_factor() const _NOEXCEPT { return __table_.max_load_factor(); }
12841296
_LIBCPP_HIDE_FROM_ABI void max_load_factor(float __mlf) { __table_.max_load_factor(__mlf); }
12851297
_LIBCPP_HIDE_FROM_ABI void rehash(size_type __n) { __table_.__rehash_unique(__n); }
12861298
_LIBCPP_HIDE_FROM_ABI void reserve(size_type __n) { __table_.__reserve_unique(__n); }

‎libcxx/test/libcxx/diagnostics/unordered_map.nodiscard.verify.cpp‎

Lines changed: 91 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -8,18 +8,99 @@
88

99
// UNSUPPORTED: c++03
1010

11-
// check that <unordered_map> functions are marked [[nodiscard]]
12-
13-
// clang-format off
11+
// Check that functions are marked [[nodiscard]]
1412

1513
#include <unordered_map>
14+
#include <utility>
1615

17-
void unordered_map_test() {
18-
std::unordered_map<int, int> unordered_map;
19-
unordered_map.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
20-
}
16+
#include "test_macros.h"
17+
18+
struct TransparentKey {};
19+
20+
struct StoredKey {
21+
friend bool operator==(StoredKey const&, StoredKey const&) { return true; }
22+
friend bool operator==(StoredKey const&, TransparentKey const&) { return true; }
23+
};
24+
25+
struct TransparentKeyHash {
26+
using is_transparent = void;
27+
28+
constexpr std::size_t operator()(TransparentKey const&) const { return 0; }
29+
constexpr std::size_t operator()(StoredKey const&) const { return 0; }
30+
};
31+
32+
void test() {
33+
std::unordered_map<int, int> m;
34+
const std::unordered_map<int, int> cm;
35+
36+
m.get_allocator(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
37+
38+
m.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
39+
m.size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
40+
m.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
41+
42+
m.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
43+
m.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
44+
cm.begin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
45+
cm.end(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
46+
cm.cbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
47+
cm.cend(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
48+
49+
int key = 0;
50+
51+
m.extract(0); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
52+
m.extract(m.begin()); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
53+
54+
m.hash_function(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
55+
m.key_eq(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
56+
57+
m.find(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
58+
cm.find(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
59+
#if TEST_STD_VER >= 20
60+
std::unordered_map<StoredKey, int, TransparentKeyHash, std::equal_to<>> tm;
61+
const std::unordered_map<StoredKey, int, TransparentKeyHash, std::equal_to<>> ctm;
62+
TransparentKey tkey;
63+
64+
tm.find(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
65+
ctm.find(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
66+
#endif
67+
68+
#if TEST_STD_VER >= 20
69+
m.count(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
70+
cm.count(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
71+
72+
tm.contains(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
73+
ctm.contains(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
74+
#endif
75+
76+
m.equal_range(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
77+
cm.equal_range(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
78+
#if TEST_STD_VER >= 20
79+
tm.equal_range(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
80+
ctm.equal_range(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
81+
#endif
82+
83+
m[key]; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
84+
m[std::move(key)]; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
85+
86+
m.at(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
87+
cm.at(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
88+
89+
m.bucket_count(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
90+
m.max_bucket_count(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
91+
92+
int size = 0;
93+
94+
m.bucket_size(size); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
95+
m.bucket(key); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
96+
97+
m.begin(size); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
98+
m.end(size); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
99+
cm.begin(size); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
100+
cm.end(size); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
101+
cm.cbegin(size); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
102+
cm.cend(size); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
21103

22-
void unordered_multimap_test() {
23-
std::unordered_multimap<int, int> unordered_multimap;
24-
unordered_multimap.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
104+
m.load_factor(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
105+
m.max_load_factor(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
25106
}

‎libcxx/test/libcxx/diagnostics/unordered_multimap.nodiscard.verify.cpp‎

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
1+
//===----------------------------------------------------------------------===//
2+
//
3+
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4+
// See https://llvm.org/LICENSE.txt for license information.
5+
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6+
//
7+
//===----------------------------------------------------------------------===//
8+
9+
// UNSUPPORTED: c++03
10+
11+
// Check that functions are marked [[nodiscard]]
12+
13+
#include <unordered_map>
14+
15+
void test() {
16+
std::unordered_multimap<int, int> unordered_multimap;
17+
18+
unordered_multimap.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
19+
}

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