From cppreference.com
A scalar object declared with the constexpr storage-class specifier is a
. It must be fully and explicitly initialized according to the static initialization rules. It still has linkage appropriate to its declaration and it exist at runtime to have its address taken; it simply cannot be modified at runtime in any way, i.e. the compiler can use its knowledge of the object’s fixed value in any other
.
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:
(except that null pointers can be constexpr),
Variably modified types,
,
types,
pointers.
Keywords
Notes
Example
Run this code
#include<fenv.h>#include<stdio.h>intmain(void){constexprfloatf=23.0f;constexprfloatg=33.0f;fesetround(FE_TOWARDZERO);constexprfloath=f/g;// is not affected by fesetround() aboveprintf("%f\n",h);}Output:
0.696969 References
C23 standard (ISO/IEC 9899:2024):
TBD TBD (p: TBD)
See also