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

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