How to declare a global const variable and initialize it with a function in C?-CodePudding

I would like to declare a constant global variable and initialize it with a function. The problem is, I can't use my function to initialize it because a function call is not a compiler-time constant, but I also can't split the declaration and the initialization as it is a const variable.

For example, the following codes are invalid.

#include <stdio.h>

int my_function(void){
    return 42;
}

const int const_variable = my_function();//invalid: my_function() is not
                                         //a compiler-time constant

/*main() here*/

#include <stdio.h>

const int const_variable;
const_variable = 10;//invalid: can't modify a const-qualified type (const int)

/*main() here*/

I looked for some answers. I saw that some people suggested the use of pointers to modify the value of a const variable after its declaration, but this could cause severe readability, portability and debugging problems.

Is there any simple, portable way to solve my problem?

CodePudding user response：

How to declare a global const variable and initialize it with a function in C?

There is no way. It is not possible.

Is there any simple, portable way to solve my problem?

No.

You can use a macro #define MY_FUNCTION() (42).

You can write a separate program, that uses that C function (or is written in a completely different language), that generates C source code with that constant and that generated source code is then compiled with your project.

Or you can switch to a different programming language with more features, for example Rust, D, C .