Re: [PATCH 1/1] git-compat-util.h: drop the `PRIuMAX` definition

From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Hariom Verma via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Hariom Verma <hariom18599@gmail.com>
Subject: Re: [PATCH 1/1] git-compat-util.h: drop the `PRIuMAX` definition
Date: Mon, 25 Nov 2019 11:24:02 +0900	[thread overview]
Message-ID: <xmqq1rtwzoal.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20191124170643.GA16907@sigill.intra.peff.net> (Jeff King's message of "Sun, 24 Nov 2019 12:06:43 -0500")

Jeff King <peff@peff.net> writes:

> On Sun, Nov 24, 2019 at 01:09:23PM +0000, Hariom Verma via GitGitGadget wrote:
>
>> From: Hariom Verma <hariom18599@gmail.com>
>> 
>> Git's code base already seems to be using `PRIdMAX` without any such
>> fallback definition for quite a while (75459410edd (json_writer: new
>> routines to create JSON data, 2018-07-13), to be precise, and the
>> first Git version to include that commit was v2.19.0).
>> 
>> Therefore it should be safe to drop the fallback definition for
>> `PRIuMAX` in `git-compat-util.h`.
>
> I noticed this recently, too, and wondered if it was time for a cleanup.

While I agree with the conclusion, I do not think I agree with the
above "Therefore (implying that the lack of need for fallback
PRIdMAX means the same for PRIuMAX) it should be safe" as a good
justification.  That reasoning assumes that the outside world is
much saner than us.  We thought PRIuMAX fallback necessary while a
counterpart for PRIdMAX unneeded---the outside world could have made
a similar mistake and in the opposite way (i.e. only defined PRIdMAX
while leaving PRIuMAX undefined).

But I do agree with the alternative justification in the following
two paragraphs you have given, which are ...

> We do sometimes get portability reports more than a year after the
> problem was introduced. But I think this one is pretty safe. PRIuMAX is
> in C99, and we've been picking up other C99-isms without complaint.
>
> I was curious what system originally spurred this. The PRIuMAX
> definition was originally added in 3efb1f343a (Check for PRIuMAX rather
> than NO_C99_FORMAT in fast-import.c., 2007-02-20). But it was replacing
> a construct that was introduced in 579d1fbfaf (Add NO_C99_FORMAT to
> support older compilers., 2006-07-30), which talks about gcc 2.95.
> That's pretty ancient at this point.

... these.

> This part of the patch looks obviously correct. :) But...
>
>>  #ifndef SCNuMAX
>>  #define SCNuMAX PRIuMAX
>>  #endif
>
> Can we likewise ditch the fallback definition for SCNuMAX? And PRIu32,
> etc? It seems likely any platform would either have all of them or none.

I guess that's also a C99-ism that we can use?

Thanks, both.