Re: [PATCH v2] conf: Stop parsing options at first non-option argument

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Aug 07, 2024 at 01:28:40PM +0200, Stefano Brivio wrote:
> Given that pasta supports specifying a command to be executed on the
> command line, even without the usual -- separator as long as there's
> no ambiguity, we shouldn't eat up options that are not meant for us.
> 
> Paul reports, for instance, that with:
> 
>   pasta --config-net ip -6 route
> 
> -6 is taken by pasta to mean --ipv6-only, and we execute 'ip route'.
> That's because getopt_long(), by default, shuffles the argument list
> to shift non-option arguments at the end.
> 
> Avoid that by adding '-' at the beginning of 'optstring', and mark the
> position of the first non-option argument (getopt_long() will now
> return the character code 1 once we hit it), so that we can use that
> as command to run, or as PID for the target namespace.
> 
> Reported-by: Paul Holzinger <pholzing@redhat.com>
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Eh... I'm kind of ambivalent about the idea.  I tend to think that
accepting options in any position is generally expected behaviour, and
anything programmatically adding commands to pasta should routinely
insert a "--" (that's certainly what I do in testing code).

But, that's not a particularly strong opinion, so whatever.

The implementation looks more complex than necessary, though.  AFAICT
if you just add a '+' to the front of the optstring it will do exactly
what you want without having to juggle the first_nonopt and other
variables.

Quoting getopt_long(3)

| By default, getopt() permutes the contents of argv as it scans, so
| that eventually all the nonoptions are at the end.  Two other
| scanning modes are also implemented.  If the first character of
| optstring is '+' or the environment variable POSIXLY_CORRECT is set,
| then option processing stops as soon as a nonoption argument is
| encountered.  If '+' is not the first character of opt‐ string, it
| is treated as a normal option.  If POSIXLY_CORRECT behaviour is
| required in this case optstring will contain two '+' symbols.  If
| the first character of optstring is '-', then each nonoption
| argv-element is handled as if it were the argument of an option with
| character code 1.  (This is used by programs that were written to
| expect options and other argv-elements in any order and that care
| about the ordering of the two.)  The special argument "--" forces an
| end of option-scanning regardless of the scanning mode.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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