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
| // RUN: %clang_cc1 -fsyntax-only -verify -std=c11 -Wno-unused %s
int f(int, int);
typedef struct A {
int x, y;
} A;
void test() {
int a;
int xs[10];
a + ++a; // expected-warning {{unsequenced modification and access to 'a'}}
a = ++a; // expected-warning {{multiple unsequenced modifications to 'a'}}
a + a++; // expected-warning {{unsequenced modification and access to 'a'}}
a = a++; // expected-warning {{multiple unsequenced modifications to 'a'}}
(a++, a++); // ok
++a + ++a; // expected-warning {{multiple unsequenced modifications}}
a++ + a++; // expected-warning {{multiple unsequenced modifications}}
a = xs[++a]; // expected-warning {{multiple unsequenced modifications}}
a = xs[a++]; // expected-warning {{multiple unsequenced modifications}}
a = (++a, ++a); // expected-warning {{multiple unsequenced modifications}}
a = (a++, ++a); // expected-warning {{multiple unsequenced modifications}}
a = (a++, a++); // expected-warning {{multiple unsequenced modifications}}
f(a, a); // ok
f(a = 0, a); // expected-warning {{unsequenced modification and access}}
f(a, a += 0); // expected-warning {{unsequenced modification and access}}
f(a = 0, a = 0); // expected-warning {{multiple unsequenced modifications}}
a = f(++a, 0); // ok
a = f(a++, 0); // ok
a = f(++a, a++); // expected-warning {{multiple unsequenced modifications}}
++a + f(++a, 0); // expected-warning {{multiple unsequenced modifications}}
f(++a, 0) + ++a; // expected-warning {{multiple unsequenced modifications}}
a++ + f(a++, 0); // expected-warning {{multiple unsequenced modifications}}
f(a++, 0) + a++; // expected-warning {{multiple unsequenced modifications}}
a = ++a; // expected-warning {{multiple unsequenced modifications}}
a += ++a; // expected-warning {{unsequenced modification and access}}
A agg1 = { a++, a++ }; // expected-warning {{multiple unsequenced modifications}}
A agg2 = { a++ + a, a++ }; // expected-warning {{unsequenced modification and access}}
(xs[2] && (a = 0)) + a; // ok
(0 && (a = 0)) + a; // ok
(1 && (a = 0)) + a; // expected-warning {{unsequenced modification and access}}
(xs[3] || (a = 0)) + a; // ok
(0 || (a = 0)) + a; // expected-warning {{unsequenced modification and access}}
(1 || (a = 0)) + a; // ok
(xs[4] ? a : ++a) + a; // ok
(0 ? a : ++a) + a; // expected-warning {{unsequenced modification and access}}
(1 ? a : ++a) + a; // ok
(xs[5] ? ++a : ++a) + a; // FIXME: warn here
(++a, xs[6] ? ++a : 0) + a; // expected-warning {{unsequenced modification and access}}
// Here, the read of the fourth 'a' might happen before or after the write to
// the second 'a'.
a += (a++, a) + a; // expected-warning {{unsequenced modification and access}}
int *p = xs;
a = *(a++, p); // ok
a = a++ && a; // ok
A *q = &agg1;
(q = &agg2)->y = q->x; // expected-warning {{unsequenced modification and access to 'q'}}
// This has undefined behavior if a == 0; otherwise, the side-effect of the
// increment is sequenced before the value computation of 'f(a, a)', which is
// sequenced before the value computation of the '&&', which is sequenced
// before the assignment. We treat the sequencing in '&&' as being
// unconditional.
a = a++ && f(a, a);
// This has undefined behavior if a != 0. FIXME: We should diagnose this.
(a && a++) + a;
(xs[7] && ++a) * (!xs[7] && ++a); // ok
xs[0] = (a = 1, a); // ok
xs[8] ? ++a + a++ : 0; // expected-warning {{multiple unsequenced modifications}}
xs[8] ? 0 : ++a + a++; // expected-warning {{multiple unsequenced modifications}}
xs[8] ? ++a : a++; // ok
xs[8] && (++a + a++); // expected-warning {{multiple unsequenced modifications}}
xs[8] || (++a + a++); // expected-warning {{multiple unsequenced modifications}}
(__builtin_classify_type(++a) ? 1 : 0) + ++a; // ok
(__builtin_constant_p(++a) ? 1 : 0) + ++a; // ok
(__builtin_expect(++a, 0) ? 1 : 0) + ++a; // expected-warning {{multiple unsequenced modifications}}
_Generic(++a, default: 0) + ++a; // ok
sizeof(++a) + ++a; // ok
_Alignof(++a) + ++a; // expected-warning {{extension}}
__builtin_constant_p(f(++a, 0)) ? f(f(++a, 0), f(++a, 0)) : 0;
if (0) ++a + ++a; // ok, unreachable
}
void g(const char *p, int n) {
// This resembles code produced by some macros in glibc's <string.h>.
__builtin_constant_p(p) && __builtin_constant_p(++n) && (++n + ++n);
}
|