Re: [PATCH 10/12] grep: change the internal PCRE macro names to be PCRE1

From: Jeff King <peff@peff.net>
Date: Apr 11, 2017, 10:35 UTC
Message-ID: <20170411103523.tlub4v65er32ikix@sigill.intra.peff.net>
In-Reply-To: <20170408132506.5415-11-avarab@gmail.com>

On Sat, Apr 08, 2017 at 01:25:04PM +0000, Ævar Arnfjörð Bjarmason wrote:

Show 19 quoted lines

> Change the internal USE_LIBPCRE define, & build options flag to use a
> naming convention ending in PCRE1, without changing the long-standing
> USE_LIBPCRE Makefile flag which enables this code.
> 
> This is for preparation for libpcre2 support where having things like
> USE_LIBPCRE and USE_LIBPCRE2 in any more places than we absolutely
> need to for backwards compatibility with old Makefile arguments would
> be confusing.
> 
> In some ways it would be better to change everything that now uses
> USE_LIBPCRE to use USE_LIBPCRE1, and to make specifying
> USE_LIBPCRE (or --with-pcre) an error. This would impose a one-time
> burden on packagers of git to s/USE_LIBPCRE/USE_LIBPCRE1/ in their
> build scripts.
> 
> However I'd like to leave the door open to making
> USE_LIBPCRE=YesPlease eventually mean USE_LIBPCRE2=YesPlease,
> i.e. once PCRE v2 is ubiquitous enough that it makes sense to make it
> the default.

Yeah, I think it's nice to keep the build-time knobs compatible. In the long run I assume we'll want to add a USE_LIBPCRE1 flag and USE_LIBPCRE just becomes a synonym for it (in fact, we could do that in this commit).

I suspect we won't ever want to make it a synonym for USE_LIBPCRE2. Unlike the run-time synonyms, where the expressions themselves are backwards compatible, builders need to care which one they're using.

-Peff