Re: [PATCH 2/4] commit-slab.h: avoid -Wsign-compare warnings

From: Jeff King <peff@peff.net>
Date: Sep 22, 2017, 15:55 UTC
Message-ID: <20170922155516.wcvpp37usb34ed3i@sigill.intra.peff.net>
In-Reply-To: <5c82e442-9d3a-d748-248d-3ea55a91f777@ramsayjones.plus.com>

On Fri, Sep 22, 2017 at 04:46:48PM +0100, Ramsay Jones wrote:

Show 14 quoted lines

> >> -	int nth_slab, nth_slot;						\
> >> +	unsigned int nth_slab, nth_slot;				\
> > 
> > I have a feeling that in the long run these should all be size_t, but
> > it's probably pretty unlikely to overflow in practice. At any rate, the
> > slab index itself is an unsigned, so it probably makes sense to match
> > that for now.
> 
> Yes, I briefly considered that, but I didn't want to think about
> possible effects of the increased size of 'struct slabname'. I suspect
> that it is very unlikely to cause an issue, but I had similar concerns
> with the 'ALLOC_GROW' patch, were it would have been more likely to
> cause memory pressure issues (to e.g. s/int/size_t/). I decided that it
> could be addressed separately, with a patch on top, if necessary.

I _think_ we'd be OK in all of those cases because these size_t's tend to be once-per-big-list, not once-per-list-item. But I agree that it would need looking into closely, and definitely should be addressed separately.

Thanks.

-Peff