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Re: [Qemu-block] [PATCH v2] qemu-io: Reinitialize optind to 1 (not 0) be

From: Eric Blake
Subject: Re: [Qemu-block] [PATCH v2] qemu-io: Reinitialize optind to 1 (not 0) before parsing inner command.
Date: Thu, 3 Jan 2019 13:46:29 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1

On 1/3/19 3:47 AM, 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.)
> Note I didn't set optreset.  It's not present in glibc and the "hard
> reset" is not necessary in this context.
> Signed-off-by: Richard W.M. Jones <address@hidden>
> ---
>  qemu-io-cmds.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Eric Blake <address@hidden>

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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