Re: the signature of getopt, and getopt_long

[Lorenzo Bettini]

Hi

on a second thought, the cast is useless:

if I have a function

f(char **argv)

that passes argv to a function

g(char * const *argv)

there's no need to cast, since this does not issue any warning: I can 
pass something not const to something that expects something cost, can't 
I? It is the other way round which does not work...

am I right?
cheers
        Lorenzo

Sergey Poznyakoff wrote:
> Hi Lorenzo,
>
> > the
> >
> > char * const *argv
> >
> > libc declaration of getopt_long (which looks wrong, since argv might
> > be changed during the parsing, right?)
>
> Yes, it is wrong because argv might be permuted by getopt_long. And
> that's why gnulib's implementation uses __getopt_argv_const in the
> declaration (see the comment in lib/getopt.in.h:73).
>
> > now, I'd like to avoid the warning in the generated parser when using
> > gnulib, but I'd like to avoid it also when using libc getopt_long
> > version...
> >
> > what would you suggest?
>
> I believe typecasting to `char *__getopt_argv_const *___argv' would be
> the best way to handle this. Keep in mind, though, that
> __getopt_argv_const is a macro, which is defined only if you include
> gnulib's version of getopt.h. Perhaps some additional #ifdef magic
> would be required before the cast, e.g.:
>
> #ifndef __getopt_argv_const
> # define __getopt_argv_const const
> #endif
>
> Regards,
> Sergey


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Lorenzo Bettini, PhD in Computer Science, DI, Univ. Torino
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