clang/test/SemaCXX/warn-tautological-compare.cpp

   1 // Force x86-64 because some of our heuristics are actually based
   2 // on integer sizes.
   3
   4 // RUN: %clang_cc1 -triple x86_64-apple-darwin -fsyntax-only -verify -std=c++11 %s
   5
   6 namespace RuntimeBehavior {
   7   // Avoid emitting tautological compare warnings when the code already has
   8   // compile time checks on variable sizes.
   9
  10   const int kintmax = 2147483647;
  11   void test0(short x) {
  12     if (sizeof(x) < sizeof(int) || x < kintmax) {}
  13
  14     if (x < kintmax) {}
  15     // expected-warning@-1{{comparison of constant 2147483647 with expression of type 'short' is always true}}
  16   }
  17
  18   void test1(short x) {
  19     if (x < kintmax) {}
  20     // expected-warning@-1{{comparison of constant 2147483647 with expression of type 'short' is always true}}
  21
  22     if (sizeof(x) < sizeof(int))
  23       return;
  24
  25     if (x < kintmax) {}
  26   }
  27 }
  28
  29 namespace ArrayCompare {
  30   #define GetValue(ptr)  ((ptr != 0) ? ptr[0] : 0)
  31   extern int a[] __attribute__((weak));
  32   int b[] = {8,13,21};
  33   struct {
  34     int x[10];
  35   } c;
  36   const char str[] = "text";
  37   void ignore() {
  38     if (a == 0) {}
  39     if (a != 0) {}
  40     (void)GetValue(b);
  41   }
  42   void test() {
  43     if (b == 0) {}
  44     // expected-warning@-1{{comparison of array 'b' equal to a null pointer is always false}}
  45     if (b != 0) {}
  46     // expected-warning@-1{{comparison of array 'b' not equal to a null pointer is always true}}
  47     if (0 == b) {}
  48     // expected-warning@-1{{comparison of array 'b' equal to a null pointer is always false}}
  49     if (0 != b) {}
  50     // expected-warning@-1{{comparison of array 'b' not equal to a null pointer is always true}}
  51     if (c.x == 0) {}
  52     // expected-warning@-1{{comparison of array 'c.x' equal to a null pointer is always false}}
  53     if (c.x != 0) {}
  54     // expected-warning@-1{{comparison of array 'c.x' not equal to a null pointer is always true}}
  55     if (str == 0) {}
  56     // expected-warning@-1{{comparison of array 'str' equal to a null pointer is always false}}
  57     if (str != 0) {}
  58     // expected-warning@-1{{comparison of array 'str' not equal to a null pointer is always true}}
  59   }
  60 }
  61
  62 namespace FunctionCompare {
  63   #define CallFunction(f) ((f != 0) ? f() : 0)
  64   extern void a()  __attribute__((weak));
  65   void fun1();
  66   int fun2();
  67   int* fun3();
  68   int* fun4(int);
  69   class S {
  70   public:
  71     static int foo();
  72   };
  73   void ignore() {
  74     if (a == 0) {}
  75     if (0 != a) {}
  76     (void)CallFunction(fun2);
  77   }
  78   void test() {
  79     if (fun1 == 0) {}
  80     // expected-warning@-1{{comparison of function 'fun1' equal to a null pointer is always false}}
  81     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
  82     if (fun2 == 0) {}
  83     // expected-warning@-1{{comparison of function 'fun2' equal to a null pointer is always false}}
  84     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
  85     // expected-note@-3{{suffix with parentheses to turn this into a function call}}
  86     if (fun3 == 0) {}
  87     // expected-warning@-1{{comparison of function 'fun3' equal to a null pointer is always false}}
  88     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
  89     // expected-note@-3{{suffix with parentheses to turn this into a function call}}
  90     if (fun4 == 0) {}
  91     // expected-warning@-1{{comparison of function 'fun4' equal to a null pointer is always false}}
  92     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
  93     if (nullptr != fun1) {}
  94     // expected-warning@-1{{comparison of function 'fun1' not equal to a null pointer is always true}}
  95     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
  96     if (nullptr != fun2) {}
  97     // expected-warning@-1{{comparison of function 'fun2' not equal to a null pointer is always true}}
  98     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
  99     if (nullptr != fun3) {}
 100     // expected-warning@-1{{comparison of function 'fun3' not equal to a null pointer is always true}}
 101     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
 102     // expected-note@-3{{suffix with parentheses to turn this into a function call}}
 103     if (nullptr != fun4) {}
 104     // expected-warning@-1{{comparison of function 'fun4' not equal to a null pointer is always true}}
 105     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
 106     if (S::foo == 0) {}
 107     // expected-warning@-1{{comparison of function 'S::foo' equal to a null pointer is always false}}
 108     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
 109     // expected-note@-3{{suffix with parentheses to turn this into a function call}}
 110   }
 111 }
 112
 113 namespace PointerCompare {
 114   extern int a __attribute__((weak));
 115   int b;
 116   static int c;
 117   class S {
 118   public:
 119     static int a;
 120     int b;
 121   };
 122   void ignored() {
 123     if (&a == 0) {}
 124   }
 125   void test() {
 126     S s;
 127     if (&b == 0) {}
 128     // expected-warning@-1{{comparison of address of 'b' equal to a null pointer is always false}}
 129     if (&c == 0) {}
 130     // expected-warning@-1{{comparison of address of 'c' equal to a null pointer is always false}}
 131     if (&s.a == 0) {}
 132     // expected-warning@-1{{comparison of address of 's.a' equal to a null pointer is always false}}
 133     if (&s.b == 0) {}
 134     // expected-warning@-1{{comparison of address of 's.b' equal to a null pointer is always false}}
 135     if (&S::a == 0) {}
 136     // expected-warning@-1{{comparison of address of 'S::a' equal to a null pointer is always false}}
 137   }
 138 }
 139
 140 namespace macros {
 141   #define assert(x) if (x) {}
 142   int array[5];
 143   void fun();
 144   int x;
 145
 146   void test() {
 147     assert(array == 0);
 148     // expected-warning@-1{{comparison of array 'array' equal to a null pointer is always false}}
 149     assert(array != 0);
 150     // expected-warning@-1{{comparison of array 'array' not equal to a null pointer is always true}}
 151     assert(array == 0 && "expecting null pointer");
 152     // expected-warning@-1{{comparison of array 'array' equal to a null pointer is always false}}
 153     assert(array != 0 && "expecting non-null pointer");
 154     // expected-warning@-1{{comparison of array 'array' not equal to a null pointer is always true}}
 155
 156     assert(fun == 0);
 157     // expected-warning@-1{{comparison of function 'fun' equal to a null pointer is always false}}
 158     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
 159     assert(fun != 0);
 160     // expected-warning@-1{{comparison of function 'fun' not equal to a null pointer is always true}}
 161     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
 162     assert(fun == 0 && "expecting null pointer");
 163     // expected-warning@-1{{comparison of function 'fun' equal to a null pointer is always false}}
 164     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
 165     assert(fun != 0 && "expecting non-null pointer");
 166     // expected-warning@-1{{comparison of function 'fun' not equal to a null pointer is always true}}
 167     // expected-note@-2{{prefix with the address-of operator to silence this warning}}
 168
 169     assert(&x == 0);
 170     // expected-warning@-1{{comparison of address of 'x' equal to a null pointer is always false}}
 171     assert(&x != 0);
 172     // expected-warning@-1{{comparison of address of 'x' not equal to a null pointer is always true}}
 173     assert(&x == 0 && "expecting null pointer");
 174     // expected-warning@-1{{comparison of address of 'x' equal to a null pointer is always false}}
 175     assert(&x != 0 && "expecting non-null pointer");
 176     // expected-warning@-1{{comparison of address of 'x' not equal to a null pointer is always true}}
 177   }
 178 }