1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
|
// RUN: %check_clang_tidy %s bugprone-unused-return-value %t -- -- -fexceptions
namespace std {
struct future {};
enum class launch {
async,
deferred
};
template <typename Function, typename... Args>
future async(Function &&, Args &&...);
template <typename Function, typename... Args>
future async(launch, Function &&, Args &&...);
template <typename ForwardIt, typename T>
ForwardIt remove(ForwardIt, ForwardIt, const T &);
template <typename ForwardIt, typename UnaryPredicate>
ForwardIt remove_if(ForwardIt, ForwardIt, UnaryPredicate);
template <typename ForwardIt>
ForwardIt unique(ForwardIt, ForwardIt);
template <typename T>
struct default_delete;
template <typename T, typename Deleter = std::default_delete<T>>
struct unique_ptr {
T *release() noexcept;
};
template <typename T>
struct char_traits;
template <typename T>
struct allocator;
template <typename CharT,
typename Traits = char_traits<CharT>,
typename Allocator = allocator<CharT>>
struct basic_string {
bool empty() const;
};
typedef basic_string<char> string;
template <typename T, typename Allocator = std::allocator<T>>
struct vector {
bool empty() const noexcept;
};
// the check should be able to match std lib calls even if the functions are
// declared inside inline namespaces
inline namespace v1 {
template <typename T>
T *launder(T *);
} // namespace v1
} // namespace std
struct Foo {
void f();
};
int increment(int i) {
return i + 1;
}
void useFuture(const std::future &fut);
void warning() {
std::async(increment, 42);
// CHECK-NOTES: [[@LINE-1]]:3: warning: the value returned by this function should be used
// CHECK-NOTES: [[@LINE-2]]:3: note: cast the expression to void to silence this warning
std::async(std::launch::async, increment, 42);
// CHECK-NOTES: [[@LINE-1]]:3: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:3: note: cast {{.*}} this warning
Foo F;
std::launder(&F);
// CHECK-NOTES: [[@LINE-1]]:3: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:3: note: cast {{.*}} this warning
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:3: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:3: note: cast {{.*}} this warning
std::remove_if(nullptr, nullptr, nullptr);
// CHECK-NOTES: [[@LINE-1]]:3: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:3: note: cast {{.*}} this warning
std::unique(nullptr, nullptr);
// CHECK-NOTES: [[@LINE-1]]:3: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:3: note: cast {{.*}} this warning
std::unique_ptr<Foo> UPtr;
UPtr.release();
// CHECK-NOTES: [[@LINE-1]]:3: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:3: note: cast {{.*}} this warning
std::string Str;
Str.empty();
// CHECK-NOTES: [[@LINE-1]]:3: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:3: note: cast {{.*}} this warning
std::vector<Foo> Vec;
Vec.empty();
// CHECK-NOTES: [[@LINE-1]]:3: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:3: note: cast {{.*}} this warning
// test discarding return values inside different kinds of statements
auto Lambda = [] { std::remove(nullptr, nullptr, 1); };
// CHECK-NOTES: [[@LINE-1]]:22: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:22: note: cast {{.*}} this warning
if (true)
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
else if (true)
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
else
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
while (true)
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
do
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
while (true);
for (;;)
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
for (std::remove(nullptr, nullptr, 1);;)
// CHECK-NOTES: [[@LINE-1]]:8: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:8: note: cast {{.*}} this warning
;
for (;; std::remove(nullptr, nullptr, 1))
// CHECK-NOTES: [[@LINE-1]]:11: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:11: note: cast {{.*}} this warning
;
for (auto C : "foo")
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
switch (1) {
case 1:
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
break;
default:
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
break;
}
try {
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
} catch (...) {
std::remove(nullptr, nullptr, 1);
// CHECK-NOTES: [[@LINE-1]]:5: warning: the value {{.*}} should be used
// CHECK-NOTES: [[@LINE-2]]:5: note: cast {{.*}} this warning
}
}
void noWarning() {
auto AsyncRetval1 = std::async(increment, 42);
auto AsyncRetval2 = std::async(std::launch::async, increment, 42);
Foo FNoWarning;
auto LaunderRetval = std::launder(&FNoWarning);
auto RemoveRetval = std::remove(nullptr, nullptr, 1);
auto RemoveIfRetval = std::remove_if(nullptr, nullptr, nullptr);
auto UniqueRetval = std::unique(nullptr, nullptr);
std::unique_ptr<Foo> UPtrNoWarning;
auto ReleaseRetval = UPtrNoWarning.release();
std::string StrNoWarning;
auto StrEmptyRetval = StrNoWarning.empty();
std::vector<Foo> VecNoWarning;
auto VecEmptyRetval = VecNoWarning.empty();
// test using the return value in different kinds of expressions
useFuture(std::async(increment, 42));
std::launder(&FNoWarning)->f();
delete std::launder(&FNoWarning);
if (std::launder(&FNoWarning))
;
for (; std::launder(&FNoWarning);)
;
while (std::launder(&FNoWarning))
;
do
;
while (std::launder(&FNoWarning));
switch (std::unique(1, 1))
;
// cast to void should allow ignoring the return value
(void)std::async(increment, 42);
// test discarding return value of functions that are not configured to be checked
increment(1);
// test that the check is disabled inside GNU statement expressions
({ std::async(increment, 42); });
auto StmtExprRetval = ({ std::async(increment, 42); });
}
|
