Here, I created the constexpr function. How to determine exactly whether it will run at compile time or at runtime?

  • Use context can add to the question? - 伪位蔚蠂慰位蠀蟿

2 answers 2

Assign its value to a variable declared as constexpr . If everything goes well, it means that it was executed at compile time :)

  • 2
    And if the function returns void ? - 伪位蔚蠂慰位蠀蟿
  • one
    and the meaning of such a function? constexpr does not have any more options how to return the result. - KoVadim
  • @KoVadim as not, out-parameters are the same - Abyx
  • Yes, of course you can, but the whole point of such functions is lost ... - KoVadim

You can try to use it in a context that involves exclusively compile-time execution. For example, static_assert :

 constexpr void f(int a) { } /*const*/ int i = 42; static_assert( (f(i),true), "");

Without const , i will have an error:

error: condition for static assertion