Question

I need to convert an enumeration member (its value, not the identifier) to a string.
I have tried the following, which works for a MACRO (TYPE_A), but not for an enum value (typeA). This is a little bit strange in my opinion.

Do you have any idea how to do this?

#define _tostr(a) #a
#define tostr(a) _tostr(a)

typedef enum _SPECIAL_FOLDER_ID {
    typeA = 3,
    typeB = 4,
} SPECIAL_FOLDER_ID;

#define TYPE_A 3

int main() {
    //this is working, but the information is a macro (TYPE_A)
    printf("The string is " tostr(TYPE_A) ".\n");

    //this is not working for typeA (defined in an enumeration)
    printf("The string is " tostr(typeA) ".\n");
    return 0;
}

The output is:

The string is 3.
The string is typeA.

I need to modify the code in some way so that the second line of the output will be “The string is 3.”

Thanks!

PS: I do not want to print the value using printf. I need a static string containing that value. I only use printf to test the result…

Answer 1

The preprocessor does not know C. It simply knows “text”.
When it processes your file, typeA is just 5 letters. Only the compiler will know (after the preprocessor is done) that typeA has a value, and that the value is 3.