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
|
// RUN: %clang_cc1 -std=c++23 -x c++ %s -verify
// RUN: %clang_cc1 -std=c++20 -pedantic -x c++ %s -verify=ext,expected
// RUN: %clang_cc1 -std=c++23 -x c++ %s -verify -fexperimental-new-constant-interpreter
// RUN: %clang_cc1 -std=c++20 -pedantic -x c++ %s -verify=ext,expected -fexperimental-new-constant-interpreter
struct A{};
struct B{ explicit operator bool() { return true; } };
template <bool cond>
void f() {
[[assume(cond)]]; // ext-warning {{C++23 extension}}
}
template <bool cond>
struct S {
void f() {
[[assume(cond)]]; // ext-warning {{C++23 extension}}
}
template <typename T>
constexpr bool g() {
[[assume(cond == sizeof(T))]]; // expected-note {{assumption evaluated to false}} ext-warning {{C++23 extension}}
return true;
}
};
bool f2();
template <typename T>
constexpr void f3() {
[[assume(T{})]]; // expected-error {{not contextually convertible to 'bool'}} expected-warning {{assumption is ignored because it contains (potential) side-effects}} ext-warning {{C++23 extension}}
}
void g(int x) {
f<true>();
f<false>();
S<true>{}.f();
S<false>{}.f();
S<true>{}.g<char>();
S<true>{}.g<int>();
[[assume(f2())]]; // expected-warning {{assumption is ignored because it contains (potential) side-effects}} ext-warning {{C++23 extension}}
[[assume((x = 3))]]; // expected-warning {{assumption is ignored because it contains (potential) side-effects}} // ext-warning {{C++23 extension}}
[[assume(x++)]]; // expected-warning {{assumption is ignored because it contains (potential) side-effects}} // ext-warning {{C++23 extension}}
[[assume(++x)]]; // expected-warning {{assumption is ignored because it contains (potential) side-effects}} // ext-warning {{C++23 extension}}
[[assume([]{ return true; }())]]; // expected-warning {{assumption is ignored because it contains (potential) side-effects}} // ext-warning {{C++23 extension}}
[[assume(B{})]]; // expected-warning {{assumption is ignored because it contains (potential) side-effects}} // ext-warning {{C++23 extension}}
[[assume((1, 2))]]; // expected-warning {{has no effect}} // ext-warning {{C++23 extension}}
f3<A>(); // expected-note {{in instantiation of}}
f3<B>(); // expected-note {{in instantiation of}}
[[assume]]; // expected-error {{takes one argument}}
[[assume(z)]]; // expected-error {{undeclared identifier}}
[[assume(A{})]]; // expected-error {{not contextually convertible to 'bool'}}
[[assume(true)]] if (true) {} // expected-error {{only applies to empty statements}}
[[assume(true)]] {} // expected-error {{only applies to empty statements}}
[[assume(true)]] for (;false;) {} // expected-error {{only applies to empty statements}}
[[assume(true)]] while (false) {} // expected-error {{only applies to empty statements}}
[[assume(true)]] label:; // expected-error {{cannot be applied to a declaration}}
[[assume(true)]] goto label; // expected-error {{only applies to empty statements}}
// Also check variant spellings.
__attribute__((__assume__(true))); // Should not issue a warning because it doesn't use the [[]] spelling.
__attribute__((assume(true))) {}; // expected-error {{only applies to empty statements}}
[[clang::assume(true)]] {}; // expected-error {{only applies to empty statements}}
}
// Check that 'x' is ODR-used here.
constexpr int h(int x) { return sizeof([=] { [[assume(x)]]; }); } // ext-warning {{C++23 extension}}
static_assert(h(4) == sizeof(int));
static_assert(__has_cpp_attribute(assume) == 202207L);
static_assert(__has_attribute(assume));
constexpr bool i() { // ext-error {{never produces a constant expression}}
[[assume(false)]]; // ext-note {{assumption evaluated to false}} expected-note {{assumption evaluated to false}} ext-warning {{C++23 extension}}
return true;
}
constexpr bool j(bool b) {
[[assume(b)]]; // expected-note {{assumption evaluated to false}} ext-warning {{C++23 extension}}
return true;
}
static_assert(i()); // expected-error {{not an integral constant expression}} expected-note {{in call to}}
static_assert(j(true));
static_assert(j(false)); // expected-error {{not an integral constant expression}} expected-note {{in call to}}
static_assert(S<true>{}.g<char>());
static_assert(S<false>{}.g<A>()); // expected-error {{not an integral constant expression}} expected-note {{in call to}}
template <typename T>
constexpr bool f4() {
[[assume(!T{})]]; // expected-error {{invalid argument type 'D'}} // expected-warning 2 {{assumption is ignored because it contains (potential) side-effects}} ext-warning {{C++23 extension}}
return sizeof(T) == sizeof(int);
}
template <typename T>
concept C = f4<T>(); // expected-note 3 {{in instantiation of}}
// expected-note@-1 3 {{while substituting}}
// expected-error@-2 2 {{resulted in a non-constant expression}}
struct D {
int x;
};
struct E {
int x;
constexpr explicit operator bool() { return false; }
};
struct F {
int x;
int y;
constexpr explicit operator bool() { return false; }
};
template <typename T>
constexpr int f5() requires C<T> { return 1; } // expected-note {{while checking the satisfaction}}
// expected-note@-1 {{while substituting template arguments}}
// expected-note@-2 {{candidate template ignored}}
template <typename T>
constexpr int f5() requires (!C<T>) { return 2; } // expected-note 4 {{while checking the satisfaction}}
// expected-note@-1 4 {{while substituting template arguments}}
// expected-note@-2 {{candidate template ignored}}
static_assert(f5<int>() == 1);
static_assert(f5<D>() == 1); // expected-note 3 {{while checking constraint satisfaction}}
// expected-note@-1 3 {{in instantiation of}}
// expected-error@-2 {{no matching function for call}}
static_assert(f5<double>() == 2);
static_assert(f5<E>() == 1); // expected-note {{while checking constraint satisfaction}} expected-note {{in instantiation of}}
static_assert(f5<F>() == 2); // expected-note {{while checking constraint satisfaction}} expected-note {{in instantiation of}}
// Do not validate assumptions whose evaluation would have side-effects.
constexpr int foo() {
int a = 0;
[[assume(a++)]] [[assume(++a)]]; // expected-warning 2 {{assumption is ignored because it contains (potential) side-effects}} ext-warning 2 {{C++23 extension}}
[[assume((a+=1))]]; // expected-warning {{assumption is ignored because it contains (potential) side-effects}} ext-warning {{C++23 extension}}
return a;
}
static_assert(foo() == 0);
template <bool ...val>
void f() {
[[assume(val)]]; // expected-error {{expression contains unexpanded parameter pack}}
}
namespace gh71858 {
int
foo (int x, int y)
{
__attribute__((assume(x == 42)));
__attribute__((assume(++y == 43))); // expected-warning {{assumption is ignored because it contains (potential) side-effects}}
return x + y;
}
}
// Do not crash when assumptions are unreachable.
namespace gh106898 {
int foo () {
while(1);
int a = 0, b = 1;
__attribute__((assume (a < b)));
}
}
|
