Re: [PATCH] compat: Allow static initializer for pthreads on Windows

From: Jeff King <peff@peff.net>
Date: Oct 27, 2016, 17:11 UTC
Message-ID: <20161027171121.tsg2gy5gov5apihq@sigill.intra.peff.net>
In-Reply-To: <CAGZ79kbP3pgPHgv-x1Q-Q1QwmXc=gOyxWhXh2SngO8WSZc3PFA@mail.gmail.com>

On Thu, Oct 27, 2016 at 10:01:02AM -0700, Stefan Beller wrote:

Show 5 quoted lines

> >  That function can
> > be called from main() of platforms that cannot statically initialize
> > mutices,
> 
> By main you mean the main() in common-main.c or cmd_main in git.c ?

Any setup or initialization for library functions needs to go in main() of common-main.c. Otherwise, only builtins get it, and external programs are left to segfault (or whatever).

> Those both look like the wrong place. Of course it would work adding it
> there, but it smells like a maintenance nightmare.

I agree it's ugly, but I suspect it would work OK in practice. We don't have that many mutexes and initializing them is cheap.

Languages like C++ have non-constant initializers, and the compiler takes care of running the startup code before main() begins. There's no portable way to do that in C, but our cmd_main() is roughly the same thing.

I still prefer the lazy initialization if it can work without incurring measurable overhead. That's the normal way to do things in C; the only complication here is the thread safety.

-Peff