self-comparison.c revision 657ca29cff71016e5300825ef539140b34fa535a 
1// RUN: %clang_cc1 -fsyntax-only -verify %s
2
3int foo(int x) {
4  return x == x; // expected-warning {{self-comparison always evaluates to true}}
5}
6
7int foo2(int x) {
8  return (x) != (((x))); // expected-warning {{self-comparison always evaluates to false}}
9}
10
11void foo3(short s, short t) {
12  if (s == s) {} // expected-warning {{self-comparison always evaluates to true}}
13  if (s == t) {} // no-warning
14}
15
16void foo4(void* v, void* w) {
17  if (v == v) {} // expected-warning {{self-comparison always evaluates to true}}
18  if (v == w) {} // no-warning
19}
20
21int qux(int x) {
22   return x < x; // expected-warning {{self-comparison}}
23}
24
25int qux2(int x) {
26   return x > x; // expected-warning {{self-comparison}}
27}
28
29int bar(float x) {
30  return x == x; // no-warning
31}
32
33int bar2(float x) {
34  return x != x; // no-warning
35}
36
37#define IS_THE_ANSWER(x) (x == 42)
38
39int macro_comparison() {
40  return IS_THE_ANSWER(42);
41}
42
43// Don't complain in unevaluated contexts.
44int compare_sizeof(int x) {
45  return sizeof(x == x); // no-warning
46}
47
48int array_comparisons() {
49  int array1[2];
50  int array2[2];
51
52  //
53  // compare same array
54  //
55  return array1 == array1; // expected-warning{{self-comparison always evaluates to true}}
56  return array1 != array1; // expected-warning{{self-comparison always evaluates to false}}
57  return array1 < array1; // expected-warning{{self-comparison always evaluates to false}}
58  return array1 <= array1; // expected-warning{{self-comparison always evaluates to true}}
59  return array1 > array1; // expected-warning{{self-comparison always evaluates to false}}
60  return array1 >= array1; // expected-warning{{self-comparison always evaluates to true}}
61
62  //
63  // compare differrent arrays
64  //
65  return array1 == array2; // expected-warning{{array comparison always evaluates to false}}
66  return array1 != array2; // expected-warning{{array comparison always evaluates to true}}
67
68  //
69  // we don't know what these are going to be
70  //
71  return array1 < array2; // expected-warning{{array comparison always evaluates to a constant}}
72  return array1 <= array2; // expected-warning{{array comparison always evaluates to a constant}}
73  return array1 > array2; // expected-warning{{array comparison always evaluates to a constant}}
74  return array1 >= array2; // expected-warning{{array comparison always evaluates to a constant}}
75
76}
77
78// Don't issue a warning when either the left or right side of the comparison
79// results from a macro expansion.  <rdar://problem/8435950>
80#define R8435950_A i
81#define R8435950_B i
82
83int R8435950(int i) {
84  if (R8435950_A == R8435950_B) // no-warning
85   return 0;
86  return 1;
87}
88
89