Re: getopt: checking exlusive options?

[Daniel Santos]

On 07/23/2013 10:55 AM, Bernhard Voelker wrote:
> Is there already something available in gnulib like
> err_exclusive_options() in util-linux [1] to automatically
> catch mutual exclusiveness of options inside the getopt loop?

After spending an inordinate amount of time experimenting with gcc's 
compile-time constant support, I'm bet that its possible to write an 
inline function that will generate a compile-time error for this! 
Basically, something like this:

extern int _getopt (int ___argc, char *const *___argv, const char 
*__shortopts) __THROW;

static inline void __validate_opts(const char *__shortopts) {
    /* insert magic here */
}

static inline int getopt (int ___argc, char *const *___argv, const char 
*__shortopts) {
    if (__builtin_constant_p(*__shortopts))
        __validate_opts(__shortopts);
    return _getopt (___argc, ___argv, __shortopts);
}

When __validate_opts() is called, we know that they have passed a 
compile-time constant value, so we can process the shortopts w/o 
worrying about a run-time overhead.  I would have to experiment further 
to figure the rest out and then see what the oldest version of gcc is 
that would treat it all as compile-time.

Daniel