constexpr specifier (since C23)

A scalar object declared with the constexpr storage-class specifier is a constant constant expression

Additionally, the constant expression that is used for the initializer of such a constant is checked at compile time.

An initializer of floating-point type must be evaluated with the translation-time floating-point environment.

There are some restrictions on the type of an object that can be declared with constexpr. Namely, the following constructs are not allowed to be constexpr:

• Pointers (except that null pointers can be constexpr),
• Variably modified types,
• Atomic types,
• volatile types,
• restrict pointers.

Keywords

constexpr

Notes

Example

#include <fenv.h>
#include <stdio.h>
 
int main(void)
{
    constexpr float f = 23.0f;
    constexpr float g = 33.0f;
    fesetround(FE_TOWARDZERO);
    constexpr float h = f / g; // is not affected by fesetround() above
    printf("%f\n", h);
}

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References

See also