Re: [PATCH] strbuf: use designated initializers in STRBUF_INIT

[Brandon Williams <bmwill@google.com>]

On 07/10, Jeff King wrote:
> On Sun, Jul 09, 2017 at 10:05:49AM -0700, Junio C Hamano wrote:
> 
> > René Scharfe <l.s.r@web.de> writes:
> > 
> > > I wonder when we can begin to target C99 in git's source, though. :)
> > 
> > Let's get the ball rolling by starting to use some of the useful
> > features like designated initializers, perhaps, in a small, critical
> > and reasonably stable part of the system that anybody must compile,
> > leave it in one full release cycle or two, and when we hear nobody
> > complains, introduce it en masse for the remainder of the system?
> > 
> > That way, we will see if there are people who need pre-C99 soon
> > enough, and we won't have to scramble reverting too many changes
> > when it happens.
> 
> Neat idea. Something like this?
> 
> -- >8 --
> Subject: [PATCH] strbuf: use designated initializers in STRBUF_INIT
> 
> There are certain C99 features that might be nice to use in
> our code base, but we've hesitated to do so in order to
> avoid breaking compatibility with older compilers. But we
> don't actually know if people are even using pre-C99
> compilers these days.
> 
> One way to figure that out is to introduce a very small use
> of a feature, and see if anybody complains. The strbuf code
> is a good place to do this for a few reasons:
> 
>   - it always gets compiled, no matter which Makefile knobs
>     have been tweaked.
> 
>   - it's very stable; this definition hasn't changed in a
>     long time and is not likely to (so if we have to revert,
>     it's unlikely to cause headaches)
> 
> If this patch can survive a few releases without complaint,
> then we can feel more confident that designated initializers
> are widely supported by our user base.  It also is an
> indication that other C99 features may be supported, but not
> a guarantee (e.g., gcc had designated initializers before
> C99 existed).
> 
> And if we do get complaints, then we'll have gained some
> data and we can easily revert this patch.
> 
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> I suspected we could also do something with __STDC_VERSION__, though I
> wonder what compilers set it to when not in standards-compliant mode.
> gcc-6 claims C11 when no specific -std flag is given.
> 
> And obviously before releasing this or anything similar, it would be
> nice to see results from people building pu. I'm especially curious
> whether MSVC would work with this (or if people even still use it, since
> Git for Windows is pretty mature?).
> 
>  strbuf.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/strbuf.h b/strbuf.h
> index 2075384e0..e705b94db 100644
> --- a/strbuf.h
> +++ b/strbuf.h
> @@ -68,7 +68,7 @@ struct strbuf {
>  };
>  
>  extern char strbuf_slopbuf[];
> -#define STRBUF_INIT  { 0, 0, strbuf_slopbuf }
> +#define STRBUF_INIT  { .alloc = 0, .len = 0, .buf = strbuf_slopbuf }

I love that this is happening!  And maybe someday soon we can do:

  for (int i = 0; i < n; i++)

So that we can scope loop variables to the loops themselves.

-- 
Brandon Williams