Re: [Qemu-devel] Can we make better use of Coverity?

[Markus Armbruster]

Paolo Bonzini <address@hidden> writes:

> On 21/01/2015 17:05, Markus Armbruster wrote:
>>>> >> What do you mean by "a GLib model"?  scripts/coverity-model.c?
>>> >
>>> > Yes.  It models g_malloc0 in a way that avoids a lot of false positives,
>>> > but still is able to flag leaks.
>> Understood.  It's hugely better than nothing,
>
> Yes, I think between false positives and false negatives it affected
> over 100 defects.

Yes.  RESOURCE_LEAK was pretty useless without it.

>> but it still can't make
>> Coverity see many relevant facts like GLib functions returning newly
>> allocated storage.  For that, you have to throw in a derived model, like
>> I do.  Unfortunately, the Scan service seems unable to do that.
>
> Right.  You can also model the functions manually, like we do for
> g_io_channel_unix_new:
>
> typedef struct _GIOChannel GIOChannel;
> GIOChannel *g_io_channel_unix_new(int fd)
> {
>     GIOChannel *c = g_malloc0(sizeof(GIOChannel));
>     __coverity_escape__(fd);
>     return c;
> }
>
> (This was done because of false positives when Coverity thought that fd
> would leak at end of scope).
>
> If you know some offenders which did cause us to leak memory in the
> past, please do submit a patch to scripts/coverity-model.c.

Comparing two local scans, one with and one without my derived model, I
think I can spot some gaps we could fill in coverity-model.c.  Stay
tuned...

> BTW, thanks for starting this thread.  We already have like 6 new users
> who will be able to see the defects and fix them!  That alone is very
> much worthy!

:)

I hope regular scanning reports to qemu-devel will get us even more.