clang/test/SemaCXX/unreachable-code.cpp

   1 // RUN: %clang_cc1 -std=c++17 -fcxx-exceptions -fexceptions -fsyntax-only -Wunreachable-code-aggressive -fblocks -verify %s
   2
   3 int j;
   4 int bar();
   5 int test1() {
   6   for (int i = 0;
   7        i != 10;
   8        ++i) {  // expected-warning {{loop will run at most once (loop increment never executed)}}
   9     if (j == 23) // missing {}'s
  10       bar();
  11       return 1;
  12   }
  13   return 0;
  14   return 1; // expected-warning {{will never be executed}}
  15 }
  16
  17 int test1_B() {
  18   for (int i = 0;
  19        i != 10;
  20        ++i) {  // expected-warning {{loop will run at most once (loop increment never executed)}}
  21     if (j == 23) // missing {}'s
  22       bar();
  23       return 1;
  24   }
  25   return 0;
  26   return bar(); // expected-warning {{will never be executed}}
  27 }
  28
  29 void test2(int i) {
  30   switch (i) {
  31   case 0:
  32     break;
  33     bar();     // expected-warning {{will never be executed}}
  34   case 2:
  35     switch (i) {
  36     default:
  37     a: goto a;
  38     }
  39     bar();     // expected-warning {{will never be executed}}
  40   }
  41   b: goto b;
  42   bar();       // expected-warning {{will never be executed}}
  43 }
  44
  45 void test3() {
  46   ^{ return;
  47      bar();    // expected-warning {{will never be executed}}
  48   }();
  49   while (++j) {
  50     continue;
  51     bar();     // expected-warning {{will never be executed}}
  52   }
  53 }
  54
  55 // PR 6130 - Don't warn about bogus unreachable code with throw's and
  56 // temporary objects.
  57 class PR6130 {
  58 public:
  59   PR6130();
  60   ~PR6130();
  61 };
  62
  63 int pr6130(unsigned i) {
  64   switch(i) {
  65     case 0: return 1;
  66     case 1: return 2;
  67     default:
  68       throw PR6130(); // no-warning
  69   }
  70 }
  71
  72 extern "C" void foo(void);
  73 extern "C" __attribute__((weak)) decltype(foo) foo;
  74
  75 void weak_redecl() {
  76   if (foo)
  77     return;
  78   bar(); // no-warning
  79 }
  80
  81 namespace pr52103 {
  82
  83 void g(int a);
  84
  85 void f(int a) {
  86   if (a > 4) [[ likely ]] { // no-warning
  87     return;
  88   }
  89
  90   if (a > 4) [[ unlikely ]] { // no-warning
  91     return;
  92
  93     return; // expected-warning {{will never be executed}}
  94   }
  95
  96   [[clang::musttail]] return g(a); // no-warning
  97
  98   [[clang::musttail]] return g(a); // expected-warning {{will never be executed}}
  99 }
 100
 101 }
 102
 103 namespace gh57123 {
 104   bool foo() {
 105     if constexpr (true) {
 106       if (true)
 107         return true;
 108       else
 109         return false; // expected-warning {{will never be executed}}
 110     }
 111     else
 112       return false; // no-warning
 113   }
 114
 115   bool bar() {
 116     if (true)
 117       return true;
 118     else
 119       return false; // expected-warning {{will never be executed}}
 120   }
 121
 122   bool baz() {
 123     if constexpr (true)
 124       return true;
 125     else {
 126       if (true)
 127         return true;
 128       else
 129         return false; // expected-warning {{will never be executed}}
 130     }
 131   }
 132 }