clang/test/Sema/c2x-fallthrough.c

   1 // RUN: %clang_cc1 -fsyntax-only -std=c2x -verify %s
   2
   3 // This is the latest version of fallthrough that we support.
   4 _Static_assert(__has_c_attribute(fallthrough) == 201910L);
   5
   6 void f(int n) {
   7   switch (n) {
   8   case 0:
   9     n += 1;
  10     [[fallthrough]]; // ok
  11   case 1:
  12     if (n) {
  13       [[fallthrough]]; // ok
  14     } else {
  15       return;
  16     }
  17   case 2:
  18     for (int n = 0; n != 10; ++n)
  19       [[fallthrough]]; // expected-error {{does not directly precede switch label}}
  20   case 3:
  21     while (1)
  22       [[fallthrough]]; // expected-error {{does not directly precede switch label}}
  23   case 4:
  24     while (0)
  25       [[fallthrough]]; // expected-error {{does not directly precede switch label}}
  26   case 5:
  27     do [[fallthrough]]; while (1); // expected-error {{does not directly precede switch label}}
  28   case 6:
  29     do [[fallthrough]]; while (0); // expected-error {{does not directly precede switch label}}
  30   case 7:
  31     switch (n) {
  32     case 0:
  33       // FIXME: This should be an error, even though the next thing we do is to
  34       // fall through in an outer switch statement.
  35       [[fallthrough]];
  36     }
  37   case 8:
  38     [[fallthrough]]; // expected-error {{does not directly precede switch label}}
  39     goto label;
  40   label:
  41   case 9:
  42     n += 1;
  43   case 10: // no warning, -Wimplicit-fallthrough is not enabled in this test, and does not need to
  44            // be enabled for these diagnostics to be produced.
  45     break;
  46   }
  47 }
  48
  49 [[fallthrough]] typedef int n1; // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
  50 typedef int [[fallthrough]] n2; // expected-error {{'fallthrough' attribute cannot be applied to types}}
  51 typedef int n3 [[fallthrough]]; // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
  52
  53 enum [[fallthrough]] E { // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
  54   One
  55 };
  56 struct [[fallthrough]] S { // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
  57   int i;
  58 };
  59
  60 [[fallthrough]] // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
  61 void g(void) {
  62   [[fallthrough]] int n; // expected-error {{'fallthrough' attribute cannot be applied to a declaration}}
  63   [[fallthrough]] ++n; // expected-error {{'fallthrough' attribute only applies to empty statements}}
  64
  65   switch (n) {
  66     // FIXME: This should be an error.
  67     [[fallthrough]];
  68     return;
  69
  70   case 0:
  71     [[fallthrough, fallthrough]]; // ok
  72   case 1:
  73     [[fallthrough(0)]]; // expected-error {{argument list}}
  74   case 2:
  75     break;
  76   }
  77 }
  78