unused-expr.c revision 46171917dc87caf0c7a741a7301f36db2e20b132 
1// RUN: %clang_cc1 -fsyntax-only -verify %s -Wno-unreachable-code
2
3int foo(int X, int Y);
4
5double sqrt(double X);  // implicitly const because of no -fmath-errno!
6
7void bar(volatile int *VP, int *P, int A,
8         _Complex double C, volatile _Complex double VC) {
9
10  VP == P;             // expected-warning {{expression result unused}}
11  (void)A;
12  (void)foo(1,2);      // no warning.
13
14  A == foo(1, 2);      // expected-warning {{expression result unused}}
15
16  foo(1,2)+foo(4,3);   // expected-warning {{expression result unused}}
17
18
19  *P;                  // expected-warning {{expression result unused}}
20  *VP;                 // no warning.
21  P[4];                // expected-warning {{expression result unused}}
22  VP[4];               // no warning.
23
24  __real__ C;          // expected-warning {{expression result unused}}
25  __real__ VC;
26
27  // We know this can't change errno because of no -fmath-errno.
28  sqrt(A);  // expected-warning {{ignoring return value of function declared with const attribute}}
29}
30
31extern void t1();
32extern void t2();
33void t3(int c) {
34  c ? t1() : t2();
35}
36
37// This shouldn't warn: the expr at the end of the stmtexpr really is used.
38int stmt_expr(int x, int y) {
39  return ({int _a = x, _b = y; _a > _b ? _a : _b; });
40}
41
42void nowarn(unsigned char* a, unsigned char* b)
43{
44  unsigned char c = 1;
45  *a |= c, *b += c;
46
47
48  // PR4633
49  int y, x;
50  ((void)0), y = x;
51}
52
53void t4(int a) {
54  int b = 0;
55
56  if (a)
57    b == 1; // expected-warning{{expression result unused}}
58  else
59    b == 2; // expected-warning{{expression result unused}}
60
61  while (1)
62    b == 3; // expected-warning{{expression result unused}}
63
64  do
65    b == 4; // expected-warning{{expression result unused}}
66  while (1);
67
68  for (;;)
69    b == 5; // expected-warning{{expression result unused}}
70
71  for (b == 1;;) {} // expected-warning{{expression result unused}}
72  for (;b == 1;) {}
73  for (;;b == 1) {} // expected-warning{{expression result unused}}
74}
75
76// rdar://7186119
77int t5f(void) __attribute__((warn_unused_result));
78void t5() {
79  t5f();   // expected-warning {{ignoring return value of function declared with warn_unused_result}}
80}
81
82
83int fn1() __attribute__ ((warn_unused_result));
84int fn2() __attribute__ ((pure));
85int fn3() __attribute__ ((const));
86// rdar://6587766
87int t6() {
88  if (fn1() < 0 || fn2(2,1) < 0 || fn3(2) < 0)  // no warnings
89    return -1;
90
91  fn1();  // expected-warning {{ignoring return value of function declared with warn_unused_result attribute}}
92  fn2(92, 21);  // expected-warning {{ignoring return value of function declared with pure attribute}}
93  fn3(42);  // expected-warning {{ignoring return value of function declared with const attribute}}
94  __builtin_fabsf(0); // expected-warning {{ignoring return value of function declared with const attribute}}
95  return 0;
96}
97
98int t7 __attribute__ ((warn_unused_result)); // expected-warning {{'warn_unused_result' attribute only applies to function types}}
99
100// PR4010
101int (*fn4)(void) __attribute__ ((warn_unused_result));
102void t8() {
103  fn4(); // expected-warning {{ignoring return value of function declared with warn_unused_result attribute}}
104}
105
106void t9() __attribute__((warn_unused_result)); // expected-warning {{attribute 'warn_unused_result' cannot be applied to functions without return value}}
107