Re: [PATCH] general style: replaces memcmp() with starts_with()

From: Jeff King <peff@peff.net>
Date: Mar 12, 2014, 18:00 UTC
Message-ID: <20140312180026.GB7982@sigill.intra.peff.net>
In-Reply-To: <532097D0.4070909@web.de>

On Wed, Mar 12, 2014 at 06:22:24PM +0100, Jens Lehmann wrote:

Show 7 quoted lines

> > Let me know if you still think the hunk should be dropped there.
> 
> Yes, I think so. That spot uses memcmp() because ce->name may
> not be 0-terminated. If that assumption isn't correct, it should
> be replaced with a plain strcmp() instead (while also dropping
> the ce_namelen() comparison in the line above). But starts_with()
> points into the wrong direction there.

I think the length-check and memcmp is an optimization[1] here. But we should be able to encapsulate that pattern and avoid magic numbers entirely with something like mem_equals(). See my other response for more details.

-Peff

[1] Getting rid of the magic number entirely means we have to call
    strlen(".gitmodules"), which seems like it is working against this
    optimization. But I think past experiments have shown that decent
    compilers will optimize strlen on a string literal to a constant, so
    as long as mem_equals is an inline, it should be equivalent.