clang/test/SemaCXX/warn-unused-comparison.cpp

   1 // RUN: %clang_cc1 -fsyntax-only -fcxx-exceptions -verify -Wno-unused -Wunused-comparison %s
   2
   3 struct A {
   4   bool operator==(const A&);
   5   bool operator!=(const A&);
   6   bool operator<(const A&);
   7   bool operator>(const A&);
   8   bool operator<=(const A&);
   9   bool operator>=(const A&);
  10   A operator|=(const A&);
  11   operator bool();
  12 };
  13
  14 void test() {
  15   int x, *p;
  16   A a, b;
  17
  18   x == 7; // expected-warning {{equality comparison result unused}} \
  19           // expected-note {{use '=' to turn this equality comparison into an assignment}}
  20   x != 7; // expected-warning {{inequality comparison result unused}} \
  21           // expected-note {{use '|=' to turn this inequality comparison into an or-assignment}}
  22   x < 7;  // expected-warning {{relational comparison result unused}}
  23   x > 7;  // expected-warning {{relational comparison result unused}}
  24   x <= 7; // expected-warning {{relational comparison result unused}}
  25   x >= 7; // expected-warning {{relational comparison result unused}}
  26
  27   7 == x; // expected-warning {{equality comparison result unused}}
  28   p == p; // expected-warning {{equality comparison result unused}} \
  29           // expected-note {{use '=' to turn this equality comparison into an assignment}} \
  30           // expected-warning {{self-comparison always evaluates to true}}
  31   a == a; // expected-warning {{equality comparison result unused}} \
  32           // expected-note {{use '=' to turn this equality comparison into an assignment}}
  33   a == b; // expected-warning {{equality comparison result unused}} \
  34           // expected-note {{use '=' to turn this equality comparison into an assignment}}
  35   a != b; // expected-warning {{inequality comparison result unused}} \
  36           // expected-note {{use '|=' to turn this inequality comparison into an or-assignment}}
  37   a < b;  // expected-warning {{relational comparison result unused}}
  38   a > b;  // expected-warning {{relational comparison result unused}}
  39   a <= b; // expected-warning {{relational comparison result unused}}
  40   a >= b; // expected-warning {{relational comparison result unused}}
  41
  42   A() == b; // expected-warning {{equality comparison result unused}}
  43   if (42) x == 7; // expected-warning {{equality comparison result unused}} \
  44                   // expected-note {{use '=' to turn this equality comparison into an assignment}}
  45   else if (42) x == 7; // expected-warning {{equality comparison result unused}} \
  46                        // expected-note {{use '=' to turn this equality comparison into an assignment}}
  47   else x == 7; // expected-warning {{equality comparison result unused}} \
  48                // expected-note {{use '=' to turn this equality comparison into an assignment}}
  49   do x == 7; // expected-warning {{equality comparison result unused}} \
  50              // expected-note {{use '=' to turn this equality comparison into an assignment}}
  51   while (false);
  52   while (false) x == 7; // expected-warning {{equality comparison result unused}} \
  53                         // expected-note {{use '=' to turn this equality comparison into an assignment}}
  54   for (x == 7; // expected-warning {{equality comparison result unused}} \
  55                // expected-note {{use '=' to turn this equality comparison into an assignment}}
  56        x == 7; // No warning -- result is used
  57        x == 7) // expected-warning {{equality comparison result unused}} \
  58                // expected-note {{use '=' to turn this equality comparison into an assignment}}
  59     x == 7; // expected-warning {{equality comparison result unused}} \
  60             // expected-note {{use '=' to turn this equality comparison into an assignment}}
  61   switch (42) default: x == 7; // expected-warning {{equality comparison result unused}} \
  62                                // expected-note {{use '=' to turn this equality comparison into an assignment}}
  63   switch (42) case 42: x == 7; // expected-warning {{equality comparison result unused}} \
  64                                // expected-note {{use '=' to turn this equality comparison into an assignment}}
  65   switch (42) {
  66     case 1:
  67     case 2:
  68     default:
  69     case 3:
  70     case 4:
  71       x == 7; // expected-warning {{equality comparison result unused}} \
  72               // expected-note {{use '=' to turn this equality comparison into an assignment}}
  73   }
  74
  75   (void)(x == 7);
  76   (void)(p == p); // expected-warning {{self-comparison always evaluates to true}}
  77   { bool b = x == 7; }
  78
  79   { bool b = ({ x == 7; // expected-warning {{equality comparison result unused}} \
  80                         // expected-note {{use '=' to turn this equality comparison into an assignment}}
  81                 x == 7; }); } // no warning on the second, its result is used!
  82
  83 #define EQ(x,y) (x) == (y)
  84   EQ(x, 5);
  85 #undef EQ
  86
  87   (void)sizeof(1 < 2, true); // No warning; unevaluated context.
  88 }
  89
  90 namespace PR10291 {
  91   template<typename T>
  92   class X
  93   {
  94   public:
  95
  96     X() : i(0) { }
  97
  98     void foo()
  99     {
 100       throw
 101         i == 0u ?
 102         5 : 6;
 103     }
 104
 105   private:
 106     int i;
 107   };
 108
 109   X<int> x;
 110 }
 111
 112 namespace PR19724 {
 113 class stream {
 114 } cout, cin;
 115
 116 stream &operator<(stream &s, int);
 117 bool operator<(stream &s, stream &s2);
 118
 119 void test() {
 120   cout < 5;    // no warning, operator returns a reference
 121   cout < cin;  // expected-warning {{relational comparison result unused}}
 122 }
 123 }
 124
 125 namespace PR19791 {
 126 struct S {
 127   void operator!=(int);
 128   int operator==(int);
 129 };
 130
 131 void test() {
 132   S s;
 133   s != 1;
 134   s == 1;  // expected-warning{{equality comparison result unused}}
 135            // expected-note@-1{{use '=' to turn this equality comparison into an assignment}}
 136 }
 137 }