Re: getopt_long_only and slightly unambiguous options

[Rich Felker <dalias@libc.org>]

On Sun, Jan 18, 2015 at 07:27:23PM +0100, Felix Janda wrote:
> Rich Felker wrote:
> > On Sun, Jan 18, 2015 at 06:51:59PM +0100, Felix Janda wrote:
> > > Hello,
> > > 
> > > since widl from wine uses the combination, get_opt_long_only seems to
> > > be supposed to be able to differentiate between a short option "-h"
> > > and a long option "--help". Together with the possibility of option
> > > abbreviations, the behavior we are trying to copy is:
> > > 
> > > -h     -> -h
> > > --help -> --help
> > > -help  -> --help
> > > -he    -> --help
> > > --h    -> --help
> > > 
> > > However musl maps all of them to --help.
> > > 
> > > The man page is ambiguous about this aspect and I'm not sure if the
> > > BSDs have the same behavior here. (However I would suspect that the
> > > breakage in widl, when the --help option was added in 2012, would
> > > have been noticed.) As always, it is hard to measure how many
> > > applications (and scripts written against these applications) might
> > > depend on this behavior. Since getopt_long_only is discouraged
> > > maybe these are actually quite few, though.
> > > 
> > > All in all I think that this a bug in musl which should be fixed.
> > > 
> > > 
> > > For the implementation, is it maybe enough in __getopt_long_core to
> > > pass options starting with '-' and of exactly two characters
> > > directly to getopt?
> > 
> > I would think getopt_long_only would even want to treat "-he" as "-h"
> > and "-e", i.e. abbreviations should be suppressed entirely when only a
> > single leading "-" appears instead of "--". However I'd rather follow
> > historical practice unless it's something stupid and complex (and
> > violating the principle of least surprise for users) like checking
> > whether each char is a valid short option and basing the decision on
> > that.
> 
> I've just checked that even when there are both -h and -e short
> options glibc getopt_long_only treats -he as --help.

OK, so I'll go ahead with making getopt_long_core ignore abbreviations
of the form "-" followed by one character.

BTW I realized another related issue we should handle -- in the case
of long options containing multibyte characters, the abbreviation code
is wrongly accepting incomplete multibyte sequences as "abbreviations"
for the full character. I don't know if this is worth fixing, It
should be as easy as checking that the next (unmatched) byte of the
full option is either in the ASCII range or is a lead-byte.

Rich