clang/test/SemaCXX/warn-constant-evaluated-constexpr.cpp

   1 // RUN: %clang_cc1 -std=c++2a -fsyntax-only -verify %s
   2 // RUN: %clang_cc1 -std=c++2a -fsyntax-only -verify %s -fexperimental-new-constant-interpreter
   3
   4 namespace std {
   5 constexpr bool is_constant_evaluated() noexcept {
   6   return __builtin_is_constant_evaluated();
   7 }
   8 } // namespace std
   9
  10 constexpr int fn1() {
  11   if constexpr (std::is_constant_evaluated()) // expected-warning {{'std::is_constant_evaluated' will always evaluate to 'true' in a manifestly constant-evaluated expression}}
  12     return 0;
  13   else
  14     return 1;
  15 }
  16
  17 constexpr int fn2() {
  18   if constexpr (!std::is_constant_evaluated()) // expected-warning {{'std::is_constant_evaluated' will always evaluate to 'true' in a manifestly constant-evaluated expression}}
  19     return 0;
  20   else
  21     return 1;
  22 }
  23
  24 constexpr int fn3() {
  25   if constexpr (std::is_constant_evaluated() == false) // expected-warning {{'std::is_constant_evaluated' will always evaluate to 'true' in a manifestly constant-evaluated expression}}
  26     return 0;
  27   else
  28     return 1;
  29 }
  30
  31 constexpr int fn4() {
  32   if constexpr (__builtin_is_constant_evaluated() == true) // expected-warning {{'__builtin_is_constant_evaluated' will always evaluate to 'true' in a manifestly constant-evaluated expression}}
  33     return 0;
  34   else
  35     return 1;
  36 }
  37
  38 constexpr int fn5() {
  39   if constexpr (__builtin_is_constant_evaluated()) // expected-warning {{'__builtin_is_constant_evaluated' will always evaluate to 'true' in a manifestly constant-evaluated expression}}
  40     return 0;
  41   else
  42     return 1;
  43 }
  44
  45 constexpr int nowarn1() {
  46   if (std::is_constant_evaluated())
  47     return 0;
  48   else
  49     return 1;
  50 }
  51
  52 constexpr int nowarn2() {
  53   if (!__builtin_is_constant_evaluated())
  54     return 0;
  55   else
  56     return 1;
  57 }