如何输出#define值

Question

I am new to this forum so please go easy on me :)

I have the following in my code

#define SYS_SBS     0x02 

Whenever I try to use this and try to output,I get 2 as the value, however I want to get SYS_SBS as the output for my program. Is there a way, I can do this.

I have no control over the source code. I just have to output SYS_SBS.

Additional Details: I cannot change some the header files. However I can change the main function in .cpp file. I want the SYS_SBS as the output. I am working with satellites and for all the satellited detected by my receiver, I have to output what type of sattelite they are. In the code all of them are defined with this hexadecimal number. I just want to output SYS_SBS and not 2

Answer 1

#include <stdio.h>

#define SYS_SBS     0x02 
#define id(x) #x

int main(){
    printf("%s %d\n", id(SYS_SBS), SYS_SBS);
    return 0;
}

Answer 2

The C standard provides a stringification operator (add a # in front of the token) that allows you to outuput a specific token.

What's not possible is to convert backwards from a variable's value to this token name as this is lost during translations (as others have mentioned). If you need that kind of conversion, think about a explicit "value2str" function that returns a string representation of a given value:

const char *myType2str(int value)
{
    switch (value)
    {
        case SYS_SBS:
            return "SYS_SBS";

        default:
            return "UNKNOWN VALUE";
    }
}

EDIT : According to some comments, stringification is part of the standard. Changed that. Thanks for the hint. Wasn't aware of that.

Answer 3

0x02 is the hexadecimal representation in the source . Once you compiled it, it's just a number (2).

\n

If you want to print it as hex, then, well... print it as hex (eg: use the formatting string "0x%.2x" ).

Well, you could simply:

printf("SYS_SBS");

But I assume you have a number as "input" (like 2), and want to output the string SYS_SBS , well, that's not directly possible. The best you can do is create a lookup table, eg:

const char* sys_strings[] = { "SYS_EX", "SYS_TEM", "SYS_SBS" };