[PATCH] strbuf: use designated initializers in STRBUF_INIT

From: Jeff King <peff@peff.net>
Date: Jul 10, 2017, 07:03 UTC
Message-ID: <20170710070342.txmlwwq6gvjkwtw7@sigill.intra.peff.net>

On Sun, Jul 09, 2017 at 10:05:49AM -0700, Junio C Hamano wrote:

Show 13 quoted lines

> 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 }
 
 /**
  * Life Cycle Functions

-- 
2.13.2.1071.gcd8104b61