Re: [Qemu-devel] [PATCH v4 0/3] Introduce vhost-user-scsi and sample application

[Felipe Franciosi]

> On 2 Mar 2017, at 17:32, Daniel P. Berrange <address@hidden> wrote:
> 
> On Thu, Mar 02, 2017 at 05:21:46PM +0000, Felipe Franciosi wrote:
>> 
>>> On 2 Mar 2017, at 17:17, Daniel P. Berrange <address@hidden> wrote:
>>> 
>>> On Thu, Mar 02, 2017 at 05:01:06PM +0000, Felipe Franciosi wrote:
>>>> Hi Eric,
>>>> 
>>>> Ping on this?
>>>> http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg06169.html
>>> 
>>> [snip]
>>> 
>>>>     CC      contrib/ivshmem-client/main.o
>>>>   
>>>> /var/tmp/patchew-tester-tmp-naxuy_ku/src/contrib/libvhost-user/libvhost-user.c:
>>>>  In function ‘vu_panic’:
>>>>   
>>>> /var/tmp/patchew-tester-tmp-naxuy_ku/src/contrib/libvhost-user/libvhost-user.c:84:5:
>>>>  error: ignoring return value of ‘vasprintf’, declared with attribute 
>>>> warn_unused_result [-Werror=unused-result]
>>>>        (void)vasprintf(&buf, msg, ap);
>>>>        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>   cc1: all warnings being treated as errors
>>> 
>>> You can side-step the issue entirely by simply not using the vasprintf
>>> function. Instead do   'buf = g_strdup_vprintf(msg, ap);' - glib does
>>> abort-on-oom, so there's no error scenario you need to handle.
>> 
>> Thanks for the pointer. That code is in libvhost-user already. I can send a 
>> separate patch to fix that if you prefer.
> 
> Yeah, it wasn't previously noticed since these files weren't compiled
> by default. Since you've added make rules to enable build, I'm afraid
> you've got the unfortunate job of cleaning up pre-existing build
> problems. I'd suggest just doing the conversion to g_strdup_vprintf()
> in the first patch your series.

That's ok. I'll wait to see if Paolo has any other comments on v4 and then I'll 
send a v5 which includes this change.

Felipe

> 
>> Just think that for this kind of usage a simple ignore_value(vasprintf(...)) 
>> is sufficient; that call is in a panic path already.
> 
> I think it is more correct to switch to g_strdup_vprintf so we get an 
> immediate
> abort, than to use ignore_value here.
> 
>> There were other cases where ignoring the return value seemed like the
>> preferred thing to do.
> 
> Thre's a few scenarios where ignoring an OOM error is appropriate, but as a
> general rule QEMU aims to abort on OOM rather than ignore it or try to handle
> it.
> 
> Regards,
> Daniel
> -- 
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