Re: Regression: git no longer works with musl libc's regex impl

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Rich,

On Tue, 4 Oct 2016, Rich Felker wrote:

> On Tue, Oct 04, 2016 at 11:27:22AM -0400, Jeff King wrote:
> > On Tue, Oct 04, 2016 at 11:08:48AM -0400, Rich Felker wrote:
> > 
> > > 1. is nonzero mod page size, it just works; the remainder of the last
> > >    page reads as zero bytes when mmapped.
> > 
> > Is that a portable assumption?
> 
> Yes.

No, it is not. You quote POSIX, but the matter of the fact is that we use
a subset of POSIX in order to be able to keep things running on Windows.

And quite honestly, there are lots of reasons to keep things running on
Windows, and even to favor Windows support over musl support. Over four
million reasons: the Git for Windows users.

So rather than getting into an ideological discussion about "broken"
systems, it would be good to keep things practical, realizing that those
users make up a very real chunk of all of Git's users.

As to making NO_REGEX conditional on REG_STARTEND: you are talking about
apples and oranges here. NO_REGEX is a Makefile flag, while REG_STARTEND
is a C preprocessor macro.

Unless you can convince the rest of the Git developers (you would not
convince me) to simulate autoconf by compiling an executable every time
`make` is run, to determine whether REG_STARTEND is defined, this is a
no-go.

However, you *can* use autoconf directly, and come up with a patch to our
configure.ac that detects the absence of REG_STARTEND and sets NO_REGEX=1.

Alternatively, you can set NO_REGEX=1 in your config.mak.

Or, if you use one of the auto-detected cases in config.mak.uname, you
could patch it to set NO_REGEX=1.

And lastly, the best alternative would be to teach musl about
REG_STARTEND, as it is rather useful a feature.

Ciao,
Johannes