20001011-1.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

extern void abort(void);
extern int strcmp(const char *, const char *);

int foo(const char *a)
{
    return strcmp(a, "main");
}

int main(void)
{
    if(foo(__FUNCTION__))
        abort();
    return 0;
}