clang/test/Sema/self-comparison.c

   1 // RUN: %clang_cc1 -fsyntax-only -verify %s
   2
   3 int foo(int x) {
   4   return x == x; // expected-warning {{self-comparison always evaluates to true}}
   5 }
   6
   7 int foo2(int x) {
   8   return (x) != (((x))); // expected-warning {{self-comparison always evaluates to false}}
   9 }
  10
  11 void 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
  16 void 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
  21 int qux(int x) {
  22    return x < x; // expected-warning {{self-comparison}}
  23 }
  24
  25 int qux2(int x) {
  26    return x > x; // expected-warning {{self-comparison}}
  27 }
  28
  29 int bar(float x) {
  30   return x == x; // no-warning
  31 }
  32
  33 int bar2(float x) {
  34   return x != x; // no-warning
  35 }
  36
  37 #define IS_THE_ANSWER(x) (x == 42)
  38
  39 int macro_comparison(void) {
  40   return IS_THE_ANSWER(42);
  41 }
  42
  43 // Don't complain in unevaluated contexts.
  44 int compare_sizeof(int x) {
  45   return sizeof(x == x); // no-warning
  46 }
  47
  48 int array_comparisons(void) {
  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 different 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.
  80 #define R8435950_A i
  81 #define R8435950_B i
  82
  83 int R8435950(int i) {
  84   if (R8435950_A == R8435950_B) // no-warning
  85    return 0;
  86   return 1;
  87 }
  88
  89 __attribute__((weak)) int weak_1[3];
  90 __attribute__((weak)) int weak_2[3];
  91 _Bool compare_weak(void) {
  92   return weak_1 == weak_2;
  93 }