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Date: Thu, 14 Jan 2016 11:14:15 +0800
From: Fam Zheng <famz@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 1/2] blockdev: Error out on negative
 throttling option values
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To: Alberto Garcia <berto@igalia.com>
Cc: Kevin Wolf <kwolf@redhat.com>, qemu-devel@nongnu.org, qemu-block@nongnu.org, Markus Armbruster <armbru@redhat.com>

On Wed, 01/13 12:13, Alberto Garcia wrote:
> On Wed 13 Jan 2016 12:02:00 PM CET, Fam Zheng wrote:
> 
> >> > Check the number range so this case is catched and reported.
> >> 
> >> I still don't know why qemu_opt_get_number() convert silently
> >> negative numbers into positive ones, shouldn't it just fail with an
> >> "invalid parameter" error?
> >
> > Because the parsing is done with strtoull(3) and unfortunately its man
> > page says "negative values are considered valid input and are silently
> > converted to the equivalent unsigned long int value."
> 
> I see... parse_uint() from cutils.c handles that by making an explicit
> check for negative numbers. It probably makes sense to apply the same
> solution (or even merge the code to the extent to which it's possible).
> 
> I also noticed that there's a couple of places where we're calling
> qemu_opt_get_number() passing -1 as default value, so maybe that API
> needs to be reviewed anyway.

Those callers rely on casting preserves the MSB as the sign, but that's ugly.
Anyway I'd leave the API change for a separate series and keep this patch local
to fix this particular regression. :)

Fam