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Re: [libvirt] [PATCH 2/6] virDomainFormatSchedDef: Handle case when func returns NULL



On Tue, May 31, 2016 at 13:32:50 +0200, Michal Privoznik wrote:
> On 31.05.2016 13:10, Peter Krempa wrote:
> > On Tue, May 31, 2016 at 13:05:16 +0200, Michal Privoznik wrote:
> >> On 31.05.2016 12:52, Peter Krempa wrote:
> >>> On Tue, May 31, 2016 at 12:33:26 +0200, Michal Privoznik wrote:
> >>>> As unlikely as it might seem, func passed to this function can
> >>>> return NULL. And in some cases it indeed does so:
> >>>> virDomainDefGetVcpuSched and virDomainDefGetIOThreadSched.
> >>>> However, the function I'm fixing blindly dereference value func
> >>>> returned thus leading to SIGSEGV.
> >>>
> >>> Same as in the coverity case complaining about this it won't happen here
> >>> since we are iterating a known list of items that was collected
> >>> beforehand and thus no crashing will happen.
> >>>
> >>
> >> Well, having covery reports a false positive is one thing, being unable
> >> to compile is another one. This is what I was afraid of and expressed it
> >> here:
> >>
> >> https://www.redhat.com/archives/libvir-list/2016-May/msg02063.html
> >>
> >> On the other hand, you use more recent compiler than I do, so you'll hit
> >> these error sooner O:-) IOW, one day we will have to deal with this. Again.
> > 
> > I'm thinking of disabling that warning at all since it's making us work
> > it around in cases where it clearly doesn't make sense. It's very
> > similar to the warning of comparison between signed and unsigned.
> > 
> 
> Is it? What about the following code:

Yes.

> 
> char *c = NULL;
> 
> *c = 'a';

How about:

int a = -1;
size_t i;

for (i = 0; i < a; i++)
   do_stuff(i);


> Should you get a warning here or not? I would like to see a warning. But

Same question. Similar source of bugs. And we've disabled it! It's a
prefernce until it creates more trouble than gain. Hence we've
disabled the -Wsign-compare flag.

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