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

[Rich Felker <dalias@libc.org>]

On Thu, Oct 06, 2016 at 03:23:40PM -0400, Jeff King wrote:
> On Thu, Oct 06, 2016 at 09:18:29PM +0200, Ævar Arnfjörð Bjarmason wrote:
> 
> > On Tue, Oct 4, 2016 at 6:08 PM, Johannes Schindelin
> > <Johannes.Schindelin@gmx.de> wrote:
> > > 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.
> > 
> > But just to clarify, does anyone have any objection to making our
> > configure.ac compile a C program to check for this sort of thing?
> > Because that seems like the easiest solution to this class of problem.
> 
> No, I think that is the exact purpose of configure.ac and autoconf.
> 
> It would be neat if we could auto-fallback during the build. Rich
> suggested always compiling compat/regex.c, and just having it be a noop
> at the preprocessor level. I'm not sure if that would work, though,
> because we'd have to include the system "regex.h" to know if we have
> REG_STARTEND, at which point it is potentially too late to compile our
> own regex routines (we're potentially going to conflict with the system
> declarations).

If you have autoconf testing for REG_STARTEND at configure time then
compat/regex.c can #include "config.h" and test for HAVE_REG_STARTEND
rather than for REG_STARTEND, or something like that.

Rich