Re: [Qemu-devel] [PATCH v4] qemu-io: Add generic function for reinitializing optind.

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Jan 18, 2019 at 10:11:14AM +0000, Richard W.M. Jones wrote:
> On FreeBSD 11.2:
> 
>   $ nbdkit memory size=1M --run './qemu-io -f raw -c "aio_write 0 512" $nbd'
>   Parsing error: non-numeric argument, or extraneous/unrecognized suffix -- aio_write
> 
> After main option parsing, we reinitialize optind so we can parse each
> command.  However reinitializing optind to 0 does not work on FreeBSD.
> What happens when you do this is optind remains 0 after the option
> parsing loop, and the result is we try to parse argv[optind] ==
> argv[0] == "aio_write" as if it was the first parameter.
> 
> The FreeBSD manual page says:
> 
>   In order to use getopt() to evaluate multiple sets of arguments, or to
>   evaluate a single set of arguments multiple times, the variable optreset
>   must be set to 1 before the second and each additional set of calls to
>   getopt(), and the variable optind must be reinitialized.
> 
> (From the rest of the man page it is clear that optind must be
> reinitialized to 1).
> 
> The glibc man page says:
> 
>   A program that scans multiple argument vectors,  or  rescans  the  same
>   vector  more than once, and wants to make use of GNU extensions such as
>   '+' and '-' at  the  start  of  optstring,  or  changes  the  value  of
>   POSIXLY_CORRECT  between scans, must reinitialize getopt() by resetting
>   optind to 0, rather than the traditional value of 1.  (Resetting  to  0
>   forces  the  invocation  of  an  internal  initialization  routine that
>   rechecks POSIXLY_CORRECT and checks for GNU extensions in optstring.)
> 
> This commit introduces an OS-portability function called
> qemu_reset_optind which provides a way of resetting optind that works
> on FreeBSD and platforms that use optreset, while keeping it the same
> as now on other platforms.
> 
> Note that the qemu codebase sets optind in many other places, but in
> those other places it's setting a local variable and not using getopt.
> This change is only needed in places where we are using getopt and the
> associated global variable optind.
> 
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> ---
>  configure            | 14 ++++++++++++++
>  include/qemu/osdep.h | 16 ++++++++++++++++
>  qemu-img.c           |  2 +-
>  qemu-io-cmds.c       |  2 +-
>  4 files changed, 32 insertions(+), 2 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>



Regards,
Daniel
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