clang/test/Sema/unused-expr.c

   1 // RUN: %clang_cc1 -fsyntax-only -verify %s -Wno-unreachable-code -Wno-strict-prototypes
   2
   3 int foo(int X, int Y);
   4
   5 double sqrt(double X);  // implicitly const because of no -fmath-errno!
   6
   7 void bar(volatile int *VP, int *P, int A,
   8          _Complex double C, volatile _Complex double VC) {
   9
  10   VP < P;              // expected-warning {{relational comparison result unused}}
  11   (void)A;
  12   (void)foo(1,2);      // no warning.
  13
  14   A < foo(1, 2);       // expected-warning {{relational comparison 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
  31 extern void t1(void);
  32 extern void t2(void);
  33 void 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.
  38 int stmt_expr(int x, int y) {
  39   return ({int _a = x, _b = y; _a > _b ? _a : _b; });
  40 }
  41
  42 void 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
  53 void t4(int a) {
  54   int b = 0;
  55
  56   if (a)
  57     b < 1; // expected-warning{{relational comparison result unused}}
  58   else
  59     b < 2; // expected-warning{{relational comparison result unused}}
  60
  61   while (1)
  62     b < 3; // expected-warning{{relational comparison result unused}}
  63
  64   do
  65     b < 4; // expected-warning{{relational comparison result unused}}
  66   while (1);
  67
  68   for (;;)
  69     b < 5; // expected-warning{{relational comparison result unused}}
  70
  71   for (b < 1;;) {} // expected-warning{{relational comparison result unused}}
  72   for (;b < 1;) {}
  73   for (;;b < 1) {} // expected-warning{{relational comparison result unused}}
  74 }
  75
  76 // rdar://7186119
  77 int t5f(void) __attribute__((warn_unused_result));
  78 void t5(void) {
  79   t5f();   // expected-warning {{ignoring return value of function declared with 'warn_unused_result' attribute}}
  80 }
  81
  82
  83 int fn1(void) __attribute__ ((warn_unused_result));
  84 int fn2() __attribute__ ((pure));
  85 int fn3() __attribute__ ((__const));
  86 // rdar://6587766
  87 int t6(void) {
  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_abs(0); // expected-warning {{ignoring return value of function declared with const attribute}}
  95   (void)0, fn1();  // expected-warning {{ignoring return value of function declared with 'warn_unused_result' attribute}}
  96   return 0;
  97 }
  98
  99 int t7 __attribute__ ((warn_unused_result)); // expected-warning {{'warn_unused_result' attribute only applies to Objective-C methods, enums, structs, unions, classes, functions, and function pointers}}
 100
 101 // PR4010
 102 int (*fn4)(void) __attribute__ ((warn_unused_result));
 103 void t8(void) {
 104   fn4(); // expected-warning {{ignoring return value of function declared with 'warn_unused_result' attribute}}
 105 }
 106
 107 void t9(void) __attribute__((warn_unused_result)); // expected-warning {{attribute 'warn_unused_result' cannot be applied to functions without return value}}
 108
 109 // rdar://7410924
 110 void *some_function(void);
 111 void t10(void) {
 112   (void*) some_function(); //expected-warning {{expression result unused; should this cast be to 'void'?}}
 113 }
 114
 115 void f(int i, ...) {
 116     __builtin_va_list ap;
 117
 118     __builtin_va_start(ap, i);
 119     __builtin_va_arg(ap, int);
 120     __builtin_va_end(ap);
 121 }
 122
 123 // PR8371
 124 int fn5(void) __attribute__ ((__const));
 125
 126 // Don't warn for unused expressions in macro bodies; however, do warn for
 127 // unused expressions in macro arguments. Macros below are reduced from code
 128 // found in the wild.
 129 #define NOP(a) (a)
 130 #define M1(a, b) (long)foo((a), (b))
 131 #define M2 (long)0;
 132 #define M3(a) (t3(a), fn2())
 133 #define M4(a, b) (foo((a), (b)) ? 0 : t3(a), 1)
 134 #define M5(a, b) (foo((a), (b)), 1)
 135 #define M6() fn1()
 136 #define M7() fn2()
 137 void t11(int i, int j) {
 138   M1(i, j);  // no warning
 139   NOP((long)foo(i, j)); // expected-warning {{expression result unused}}
 140   M2;  // no warning
 141   NOP((long)0); // expected-warning {{expression result unused}}
 142   M3(i); // no warning
 143   NOP((t3(i), fn2())); // expected-warning {{ignoring return value}}
 144   M4(i, j); // no warning
 145   NOP((foo(i, j) ? 0 : t3(i), 1)); // expected-warning {{expression result unused}}
 146   M5(i, j); // no warning
 147   NOP((foo(i, j), 1)); // expected-warning {{expression result unused}}
 148   M6(); // expected-warning {{ignoring return value}}
 149   M7(); // no warning
 150 }
 151 #undef NOP
 152 #undef M1
 153 #undef M2
 154 #undef M3
 155 #undef M4
 156 #undef M5
 157 #undef M6
 158 #undef M7
 159
 160 #define UNREFERENCED_PARAMETER(x) (x)
 161
 162 void unused_parm(int a) {
 163   // Don't warn if the warning is introduced by a macro that's spelled
 164   // UNREFERENCED_PARAMETER, as that's a commonly used macro in Windows headers.
 165   UNREFERENCED_PARAMETER(a);
 166 }