Re: [Xen-devel] [PATCH v4 1/2] libxl: Introduce functions to add and remove USB devices to an HVM guest

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 17/04/13 10:58, Ian Campbell wrote:
> On Tue, 2013-04-16 at 19:00 +0100, Roger Pau Monnà wrote:
>
> > > +    libxl_usb_path = libxl__sprintf(gc, "%s/usb", libxl_path);
> > I would recommend to use GCSPRINTF instead, it already checks for errors
> GCSPRINTF and libxl__sprintf have the same amount of error checking.
>
> The more important point is that the libxl memory allocation
> functions/macros all panic on ENOMEM so there is no need for code in
> general to check for allocation errors.
>
> i.e. This block...
> > > +    if (!libxl_usb_path) {
> > > +        LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "cannot allocate create paths");
> > > +        rc = ERROR_FAIL;
> > > +        goto out;
> > > +    }
> ...is unneeded. I didn't check the rest of the patch but I imagine you
> are in the habits of checking errors and can now remove a bunch of
> code ;-)
OK -- well in that block in particular, it's following suit with the 
rest of the surrounding code which does exactly the same thing.  As I 
said in another e-mail to roger about error checking in this function, I 
think that it's more important for programmers to be able to see this is 
exactly the same as all the rest.  At some point there should probably 
be a clean-up to remove the check from all of them, but I don't think 
that's worth the risk at this point in the release cycle.
I can put cleaning up this function on my to-do list for the 4.4 dev 
cycle if you want.
 -George

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