Re: [PATCH v8 0/7] Add pci_dev_for_each_resource() helper and update users

[Andy Shevchenko]

On Thu, Jun 01, 2023 at 07:25:46PM +0300, Andy Shevchenko wrote:
> On Wed, May 31, 2023 at 08:48:35PM +0200, Jonas Gorski wrote:
> > On Tue, 30 May 2023 at 23:34, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> > > On Fri, May 12, 2023 at 02:48:51PM -0500, Bjorn Helgaas wrote:

...

> > > Where are we at?  Are we going to ignore this because some Coverity
> > > reports are false positives?
> > 
> > Looking at the code I understand where coverity is coming from:
> > 
> > #define __pci_dev_for_each_res0(dev, res, ...)                         \
> >        for (unsigned int __b = 0;                                      \
> >             res = pci_resource_n(dev, __b), __b < PCI_NUM_RESOURCES;   \
> >             __b++)
> > 
> >  res will be assigned before __b is checked for being less than
> > PCI_NUM_RESOURCES, making it point to behind the array at the end of
> > the last loop iteration.
> 
> Which is fine and you stumbled over the same mistake I made, that's why the
> documentation has been added to describe why the heck this macro is written
> the way it's written.
> 
> Coverity sucks.
> 
> > Rewriting the test expression as
> > 
> > __b < PCI_NUM_RESOURCES && (res = pci_resource_n(dev, __b));
> > 
> > should avoid the (coverity) warning by making use of lazy evaluation.
> 
> Obviously NAK.
> 
> > It probably makes the code slightly less performant as res will now be
> > checked for being not NULL (which will always be true), but I doubt it
> > will be significant (or in any hot paths).

Oh my god, I mistakenly read this as bus macro, sorry for my rant,
it's simply wrong.

-- 
With Best Regards,
Andy Shevchenko