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From: Rich Felker <dalias@libc.org>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Jeff King <peff@peff.net>, git@vger.kernel.org, musl@lists.openwall.com
Subject: Re: [musl] Re: Regression: git no longer works with musl libc's regex impl
Date: Tue, 4 Oct 2016 13:39:26 -0400	[thread overview]
Message-ID: <20161004173926.GA19318@brightrain.aerifal.cx> (raw)
In-Reply-To: <alpine.DEB.2.20.1610041802310.35196@virtualbox>

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

  parent reply	other threads:[~2016-10-04 17:39 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-04 15:08 Rich Felker
2016-10-04 15:27 ` Jeff King
2016-10-04 15:40   ` Rich Felker
2016-10-04 16:08     ` Johannes Schindelin
2016-10-04 16:11       ` Rich Felker
2016-10-04 17:16         ` Johannes Schindelin
2016-10-04 18:00           ` Ray Donnelly
2016-10-04 17:39       ` Rich Felker [this message]
2016-10-05 11:17         ` [musl] " Johannes Schindelin
2016-10-05 13:01           ` Szabolcs Nagy
2016-10-05 13:15           ` Rich Felker
2016-10-04 22:06       ` James B
2016-10-04 22:33         ` Rich Felker
2016-10-04 22:48           ` Junio C Hamano
2016-10-05 13:11           ` Jakub Narębski
2016-10-05 16:15             ` [musl] " Rich Felker
2016-10-05 10:41         ` Johannes Schindelin
2016-10-05 11:59           ` James B
2016-10-05 16:11             ` Jeff King
2016-10-05 16:27               ` Rich Felker
2016-10-06 10:44             ` Johannes Schindelin
2016-10-06 19:18       ` Ævar Arnfjörð Bjarmason
2016-10-06 19:23         ` Jeff King
2016-10-06 19:25           ` Rich Felker
2016-10-06 19:28             ` Jeff King
2016-10-06 22:42         ` Ramsay Jones
2016-10-07 11:30           ` Jakub Narębski
2016-10-04 16:01   ` Johannes Schindelin
2016-10-05  3:00 [musl] " writeonce
2016-10-05 10:49 ` Johannes Schindelin
2016-10-05 16:37 writeonce

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