Re: [PATCH v2 1/2] storage-daemon: report unexpected arguments on the fly

[Markus Armbruster]

Eric Blake <eblake@redhat.com> writes:

> On 3/1/21 9:28 AM, Paolo Bonzini wrote:
>> 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 removes the reordering of the argv array, and enables usage
>> of loc_set_cmdline to provide better error messages.
>> 
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>>  storage-daemon/qemu-storage-daemon.c | 9 ++++-----
>>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> Nice.  The man page for 'getopt_long' is unclear whether setting
> POSIXLY_CORRECT in the environment would break this (that is, setting
> POSIXLY_CORRECT has the same effect as a leading '+'; but you can't have
> both leading '+' and leading '-' and when both are set, it is not clear
> which one wins).  But that's a corner case that I don't think will ever
> bite us in real life.
>
> Reviewed-by: Eric Blake <eblake@redhat.com>

I'd consider environment overruling the programmer's express intent a
bug.

GLibc's _getopt_initialize():

  /* Determine how to handle the ordering of options and nonoptions.  */
  if (optstring[0] == '-')
    {
      d->__ordering = RETURN_IN_ORDER;
      ++optstring;
    }
  else if (optstring[0] == '+')
    {
      d->__ordering = REQUIRE_ORDER;
      ++optstring;
    }
  else if (posixly_correct || !!getenv ("POSIXLY_CORRECT"))
    d->__ordering = REQUIRE_ORDER;
  else
    d->__ordering = PERMUTE;

No surprises here.