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Message-ID: <20161004173926.GA19318@brightrain.aerifal.cx>
Date: Tue, 4 Oct 2016 13:39:26 -0400
From: Rich Felker <dalias@...c.org>
To: Johannes Schindelin <Johannes.Schindelin@....de>
Cc: Jeff King <peff@...f.net>, git@...r.kernel.org, musl@...ts.openwall.com
Subject: Re: Re: Regression: git no longer works with musl libc's
regex impl
On Tue, Oct 04, 2016 at 06:08:33PM +0200, Johannes Schindelin wrote:
> 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.
It seems like you could just always compile the source file, and just
have it all inside #if defined(NO_REGEX) || !defined(REG_STARTEND) or
similar.
> And lastly, the best alternative would be to teach musl about
> REG_STARTEND, as it is rather useful a feature.
Maybe, but it seems fundamentally costly to support -- it's extra
state in the inner loops that imposes costly spill/reload on archs
with too few registers (x86). I'll look at doing this when we
overhaul/replace the regex implementation, and I'm happy to do some
performance-regression tests for adding it now if someone has a simple
patch (as was mentioned on the musl list).
Rich
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