1 // RUN: %clang_cc1 -fsyntax-only -verify -std=c11 -Wno-unused %s
2
3 int f(int, int);
4
5 typedef struct A {
6 int x, y;
7 } A;
8
test()9 void test() {
10 int a;
11 int xs[10];
12 a + ++a; // expected-warning {{unsequenced modification and access to 'a'}}
13 a = ++a; // expected-warning {{multiple unsequenced modifications to 'a'}}
14 a + a++; // expected-warning {{unsequenced modification and access to 'a'}}
15 a = a++; // expected-warning {{multiple unsequenced modifications to 'a'}}
16 (a++, a++); // ok
17 ++a + ++a; // expected-warning {{multiple unsequenced modifications}}
18 a++ + a++; // expected-warning {{multiple unsequenced modifications}}
19 a = xs[++a]; // expected-warning {{multiple unsequenced modifications}}
20 a = xs[a++]; // expected-warning {{multiple unsequenced modifications}}
21 a = (++a, ++a); // expected-warning {{multiple unsequenced modifications}}
22 a = (a++, ++a); // expected-warning {{multiple unsequenced modifications}}
23 a = (a++, a++); // expected-warning {{multiple unsequenced modifications}}
24 f(a, a); // ok
25 f(a = 0, a); // expected-warning {{unsequenced modification and access}}
26 f(a, a += 0); // expected-warning {{unsequenced modification and access}}
27 f(a = 0, a = 0); // expected-warning {{multiple unsequenced modifications}}
28 a = f(++a, 0); // ok
29 a = f(a++, 0); // ok
30 a = f(++a, a++); // expected-warning {{multiple unsequenced modifications}}
31
32 ++a + f(++a, 0); // expected-warning {{multiple unsequenced modifications}}
33 f(++a, 0) + ++a; // expected-warning {{multiple unsequenced modifications}}
34 a++ + f(a++, 0); // expected-warning {{multiple unsequenced modifications}}
35 f(a++, 0) + a++; // expected-warning {{multiple unsequenced modifications}}
36
37 a = ++a; // expected-warning {{multiple unsequenced modifications}}
38 a += ++a; // expected-warning {{unsequenced modification and access}}
39
40 A agg1 = { a++, a++ }; // expected-warning {{multiple unsequenced modifications}}
41 A agg2 = { a++ + a, a++ }; // expected-warning {{unsequenced modification and access}}
42
43 (xs[2] && (a = 0)) + a; // expected-warning {{unsequenced modification and access to 'a'}}
44 (0 && (a = 0)) + a; // ok
45 (1 && (a = 0)) + a; // expected-warning {{unsequenced modification and access}}
46
47 (xs[3] || (a = 0)) + a; // expected-warning {{unsequenced modification and access to 'a'}}
48 (0 || (a = 0)) + a; // expected-warning {{unsequenced modification and access}}
49 (1 || (a = 0)) + a; // ok
50
51 (xs[4] ? a : ++a) + a; // expected-warning {{unsequenced modification and access to 'a'}}
52 (0 ? a : ++a) + a; // expected-warning {{unsequenced modification and access}}
53 (1 ? a : ++a) + a; // ok
54 (xs[5] ? ++a : ++a) + a; // expected-warning {{unsequenced modification and access to 'a'}}
55
56 (++a, xs[6] ? ++a : 0) + a; // expected-warning {{unsequenced modification and access}}
57
58 // Here, the read of the fourth 'a' might happen before or after the write to
59 // the second 'a'.
60 a += (a++, a) + a; // expected-warning {{unsequenced modification and access}}
61
62 int *p = xs;
63 a = *(a++, p); // ok
64 a = a++ && a; // ok
65
66 A *q = &agg1;
67 (q = &agg2)->y = q->x; // expected-warning {{unsequenced modification and access to 'q'}}
68
69 // This has undefined behavior if a == 0; otherwise, the side-effect of the
70 // increment is sequenced before the value computation of 'f(a, a)', which is
71 // sequenced before the value computation of the '&&', which is sequenced
72 // before the assignment. We treat the sequencing in '&&' as being
73 // unconditional.
74 a = a++ && f(a, a);
75
76 // This has undefined behavior if a != 0.
77 (a && a++) + a; // expected-warning {{unsequenced modification and access to 'a'}}
78
79 // FIXME: Find a way to avoid warning here.
80 (xs[7] && ++a) * (!xs[7] && ++a); // expected-warning {{multiple unsequenced modifications to 'a'}}
81
82 xs[0] = (a = 1, a); // ok
83
84 xs[8] ? ++a + a++ : 0; // expected-warning {{multiple unsequenced modifications}}
85 xs[8] ? 0 : ++a + a++; // expected-warning {{multiple unsequenced modifications}}
86 xs[8] ? ++a : a++; // ok
87
88 xs[8] && (++a + a++); // expected-warning {{multiple unsequenced modifications}}
89 xs[8] || (++a + a++); // expected-warning {{multiple unsequenced modifications}}
90
91 (__builtin_classify_type(++a) ? 1 : 0) + ++a; // ok
92 (__builtin_constant_p(++a) ? 1 : 0) + ++a; // ok
93 (__builtin_expect(++a, 0) ? 1 : 0) + ++a; // expected-warning {{multiple unsequenced modifications}}
94 _Generic(++a, default: 0) + ++a; // ok
95 sizeof(++a) + ++a; // ok
96 _Alignof(++a) + ++a; // expected-warning {{extension}}
97
98 __builtin_constant_p(f(++a, 0)) ? f(f(++a, 0), f(++a, 0)) : 0;
99
100 if (0) ++a + ++a; // ok, unreachable
101 }
102
g(const char * p,int n)103 void g(const char *p, int n) {
104 // This resembles code produced by some macros in glibc's <string.h>.
105 __builtin_constant_p(p) && __builtin_constant_p(++n) && (++n + ++n);
106 }
107