Re: [PATCH] git-compat-util.h: Fix build without threads

From: Jeff King <peff@peff.net>
Date: Nov 28, 2022, 05:04 UTC
Message-ID: <Y4RBUa5ILEszSpOu@coredump.intra.peff.net>
In-Reply-To: <221126.86lenymw7p.gmgdl@evledraar.gmail.com>

On Sat, Nov 26, 2022 at 12:47:27AM +0100, Ævar Arnfjörð Bjarmason wrote:

Show 23 quoted lines

> On Fri, Nov 25 2022, Bagas Sanjaya wrote:
> 
> > From: Fabrice Fontaine <fontaine.fabrice@gmail.com>
> >
> > Git build with toolchains without threads support is broken (as reported
> > by Buildroot autobuilder [1]) since version 2.29.0, which traces back to
> 
> > --- a/git-compat-util.h
> > +++ b/git-compat-util.h
> > @@ -1470,7 +1470,8 @@ int open_nofollow(const char *path, int flags);
> >  # define SHELL_PATH "/bin/sh"
> >  #endif
> >  
> > -#ifndef _POSIX_THREAD_SAFE_FUNCTIONS
> > +
> > +#if !defined(_POSIX_THREAD_SAFE_FUNCTIONS) && defined(NO_FLOCKFILE)
> 
> Per f43cce23add (git-compat-util: add fallbacks for unlocked stdio,
> 2015-04-16) wouldn't it make more sense to do something like:
> 
> #ifdef NO_FLOCKFILE
> #undef _POSIX_THREAD_SAFE_FUNCTIONS
> #endif

That doesn't work, because the NO_FLOCKFILE is actually overriding the _lack_ of _POSIX_THREAD_SAFE_FUNCTIONS. So it's kind of confusingly named. In this patch, NO_FLOCKFILE means "do not define a noop wrapper flockfile()", which can only work if the system really does define it.

I do think this patch is doing the wrong thing, though. See my other reply.

-Peff