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From:   Eric Sunshine <sunshine@sunshineco.com>
Date:   Tue, 17 Nov 2020 18:07:07 -0500
Message-ID: <CAPig+cQnA_zqtjOu2OryM57jVMQeo32U3iBYVzxFkPnZ9Zd+cA@mail.gmail.com>
Subject: Re: [PATCH] list-objects-filter-options: fix function name in BUG
To:     Jeff King <peff@peff.net>
Cc:     =?UTF-8?Q?Martin_=C3=85gren?= <martin.agren@gmail.com>,
        Git Mailing List <git@vger.kernel.org>,
        Taylor Blau <me@ttaylorr.com>
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On Tue, Nov 17, 2020 at 5:55 PM Jeff King <peff@peff.net> wrote:
> I actually wonder if it is time to drop HAVE_VARIADIC_MACROS completely.
> They are in C99, and we have been introducing many other C99-isms. It
> would be a minor cleanup to a few bits of code, which perhaps isn't
> worth the risk. But I also have a vague memory of not being able to
> implement some interfaces because we couldn't count on them.
>
> Poking around, 3689539127 (add helpers for allocating flex-array
> structs, 2016-02-22) points out one such case. I think discussion of
> BUG_ON() got blocked by that, too. Looks like we also discussed them in
> the big "C99 weather balloon" thread:

There was also an idea[1] to use variadic macros to prevent `errno`
from being clobbered in a case like this:

    die_errno(_("blah %s"), foobar());

In which, if foobar() changes `errno`, then die_errno() reports the wrong value.

[1]: https://lore.kernel.org/git/CAPig+cQKMxwadf9aGyC5ESa-vxDy9PzrYo+m+JaVQ3S=12PyQQ@mail.gmail.com/