Question

#include <stdio.h>

#define STR(x) #x
#define STR2(x) STR(x)
#define LINE_FILE ("Line " STR2(__LINE__) " of file " STR2(__FILE__))

int main(void)
{
    const char *str = LINE_FILE;

    printf("%s\n", str);

    return 0;
}

Is this the only definition scheme that will make STR(x) to print the actual LINE and FILE???

Answer 1

STR2(__FILE__)

__FILE__ is already a string literal: you don’t need to use STR2 here.

You should also probably remove the parentheses from the macro so that it can be concatenated with other string literals, if you wanted to do that:

#define LINE_FILE "Line " STR2(__LINE__) " of file " __FILE__