test/Analysis/unreachable-code-path.c

   1 // RUN: %clang_cc1 -analyze -analyzer-experimental-checks -analyzer-check-objc-mem -analyzer-check-dead-stores -verify -analyzer-opt-analyze-nested-blocks -Wno-unused-value %s
   2
   3 extern void foo(int a);
   4
   5 // The first few tests are non-path specific - we should be able to find them
   6
   7 void test(unsigned a) {
   8   switch (a) {
   9     a += 5; // expected-warning{{never executed}}
  10   case 2:
  11     a *= 10;
  12   case 3:
  13     a %= 2;
  14   }
  15   foo(a);
  16 }
  17
  18 void test2(unsigned a) {
  19  help:
  20   if (a > 0)
  21     return;
  22   if (a == 0)
  23     return;
  24   foo(a); // expected-warning{{never executed}}
  25   goto help;
  26 }
  27
  28 void test3(unsigned a) {
  29   while(1);
  30   if (a > 5) { // expected-warning{{never executed}}
  31     return;
  32   }
  33 }
  34
  35 // These next tests are path-sensitive
  36
  37 void test4() {
  38   int a = 5;
  39
  40   while (a > 1)
  41     a -= 2;
  42
  43   if (a > 1) {
  44     a = a + 56; // expected-warning{{never executed}}
  45   }
  46
  47   foo(a);
  48 }
  49
  50 extern void bar(char c);
  51
  52 void test5(const char *c) {
  53   foo(c[0]);
  54
  55   if (!c) {
  56     bar(1); // expected-warning{{never executed}}
  57   }
  58 }
  59
  60 // These next tests are false positives and should not generate warnings
  61
  62 void test6(const char *c) {
  63   if (c) return;
  64   if (!c) return;
  65   __builtin_unreachable(); // no-warning
  66 }
  67
  68 // Compile-time constant false positives
  69 #define CONSTANT 0
  70 enum test_enum { Off, On };
  71 void test7() {
  72   if (CONSTANT)
  73     return; // no-warning
  74
  75   if (sizeof(int))
  76     return; // no-warning
  77
  78   if (Off)
  79     return; // no-warning
  80 }
  81
  82 void test8() {
  83   static unsigned a = 0;
  84
  85   if (a)
  86     a = 123; // no-warning
  87
  88   a = 5;
  89 }
  90
  91 // Check for bugs where multiple statements are reported
  92 void test9(unsigned a) {
  93   switch (a) {
  94     if (a) // expected-warning{{never executed}}
  95       foo(a + 5); // no-warning
  96     else          // no-warning
  97       foo(a);     // no-warning
  98     case 1:
  99     case 2:
 100       break;
 101     default:
 102       break;
 103   }
 104 }
 105
 106 // Tests from flow-sensitive version
 107 void test10() {
 108   goto c;
 109   d:
 110   goto e; // expected-warning {{never executed}}
 111   c: ;
 112   int i;
 113   return;
 114   goto b; // expected-warning {{never executed}}
 115   goto a; // expected-warning {{never executed}}
 116   b:
 117   i = 1; // no-warning
 118   a:
 119   i = 2;  // no-warning
 120   goto f;
 121   e:
 122   goto d;
 123   f: ;
 124 }