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Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables |
Date: |
Fri, 19 Jul 2013 05:13:19 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 |
On 07/19/2013 05:04 AM, Pawit Pornkitprasan wrote:
> On Fri, Jul 19, 2013 at 7:57 PM, Eric Blake <address@hidden> wrote:
>>
>> However, wouldn't it be nice if we improved the qapi generator to
>> guarantee a sane default value for optional parameters, even when
>> has_value is false?
>>
>
> I'm not a qemu expert or anything, but wouldn't that destroy the point
> of has_value in the first place?
There are two uses for has_value. One: on output, the user knows
whether the variable has been set to anything sane. Two: on input, the
receiver knows if the caller passed an optional value. For output,
has_value is always needed. But for input, we could probably simplify a
LOT of code if 'value' already had a sane default of 0, without having
to first check 'has_value', instead of the current state where 'value'
must be treated as uninitialized if 'has_value' is false. Improving the
qapi generator to guarantee 0 value of optional parameters that were not
specified in JSON should not block your patch (it would be a series by
itself), it's just a question of whether it is worth making the change
and the resulting simplifications we can make to code that can assume
sane default values.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Pawit Pornkitprasan, 2013/07/19
- Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Eric Blake, 2013/07/19
- Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Pawit Pornkitprasan, 2013/07/19
- Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables,
Eric Blake <=
- Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Luiz Capitulino, 2013/07/29
- Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Markus Armbruster, 2013/07/29
- Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Anthony Liguori, 2013/07/29
- Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Markus Armbruster, 2013/07/30
- Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Anthony Liguori, 2013/07/30
- Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Markus Armbruster, 2013/07/30
Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Orit Wasserman, 2013/07/22
Re: [Qemu-devel] [PATCH] migration: don't use uninitialized variables, Luiz Capitulino, 2013/07/29