Re: [PATCH] describe: fix --no-exact-match

From: Jeff King <peff@peff.net>
Date: Aug 10, 2023, 00:26 UTC
Message-ID: <20230810002638.GC795985@coredump.intra.peff.net>
In-Reply-To: <xmqqzg30m3vo.fsf@gitster.g>

On Wed, Aug 09, 2023 at 12:07:07PM -0700, Junio C Hamano wrote:

Show 12 quoted lines

> But I am failing to imagine how the calling side actually would look
> like.  Can we do something along the lines of
> 
>     #define OPT_CALLBACK(s, l, v, a, h, cb)
> 	.short_name = (s),
> 	.long_name = (l),
> 	.value_ ## typeof(v) = &v,
> 	.help = (h),
> 	.callback = (cb),
> 
> with a clever CPP trick?  It sounds like either too much churn or
> too much magic or both, at least to me.

Sadly, I think "typeof" is not sufficiently portable, and there is no replacement. You'd have to do something like:

  int my_foo;
  ...
  OPT_CALLBACK('f', "foo", int, &my_foo, ...etc);

Not great, but it might not be _too_ bad given that most helpers like OPT_BOOL() can just say "int" behind the scenes.

That said, I don't recall these void pointers being a large source of errors in the past. So while it's a fun type-system puzzle, the effort/reward ratio might not be favorable.

-Peff