Re: Fixing the warning about warning(""); was: Re: [PATCH] difftool.c: mark a file-local symbol with static

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Jan 26, 2017, 11:37 UTC
Message-ID: <alpine.DEB.2.20.1701261226220.3469@virtualbox>
In-Reply-To: <546179e0-1d6e-86f7-00cf-e13218b76de1@kdbg.org>

Hi Hannes,

On Thu, 26 Jan 2017, Johannes Sixt wrote:

Show 5 quoted lines

> Am 25.01.2017 um 23:01 schrieb Jeff King:
> > +#pragma GCC diagnostic ignored "-Wformat-zero-length"
> 
> Last time I used #pragma GCC in a cross-platform project, it triggered
> an "unknown pragma" warning for MSVC.

It is starting to become a little funny how many ways we can discuss the resolution of the GCC compiler warning.

And it starts to show: we try to solve the thing in so many ways, just to avoid the obviously most-trivial patch to change warning(""); to warning("%s", "") (the change to warning(" "); would change behavior, but I would be fine with that, too).

I am not really interested in any of these complicated workarounds. If you gentle people decide they are better in Git's source code, go ahead. I do not have to like what you are doing, I just have to work with it.

Show 7 quoted lines

> (It was the C++ compiler, I don't know if the C compiler would also
> warn.) It would have to be spelled like this:
> 
> #pragma warning(disable: 4068)   /* MSVC: unknown pragma */
> #pragma GCC diagnostic ignored "-Wformat-zero-length"
> 
> Dscho mentioned that he's compiling with MSVC. It would do him a favor.

I am compiling with MSVC, and the idea is to tap into that large number of Windows developers who Git traditionally has had a really bad time attracting. From that perspective, I would say it would not only do me a favor, but anybody who builds Git for Windows using Visual Studio.

But we also have to consider whether it would do anybody a "dis-favor". #pragma statements are by definition highly dependent on the compiler. I have no idea whether there are developers out there building Git with C compilers other than GCC, clang or MSVC (as I did back in the days on IRIX and HP/UX), but there is quite the potential for problems here [*1*].

To keep Git's source code truly portable, the #pragma would have to be guarded by a GCC-specific #ifdef ... #endif.

Ciao, Dscho

Footnote *1*: This is just another instance where a discussion on the Git mailing list reminds me of http://thedailywtf.com/articles/The_Complicator_0x27_s_Gloves, as it tries to avoid an obvious solution by trying to come up with a different solution that in turn requires additional solutions to additional problems caused by the alternative solution.