[cfe-commits] [Patch] -Wformat-non-standard: warn about positional arguments (pr12017)

[Ted Kremenek]

On Feb 28, 2012, at 3:03 AM, Hans Wennborg <hans at chromium.org> wrote:

> On Mon, Feb 27, 2012 at 20:00, Ted Kremenek <kremenek at apple.com> wrote:
>> For me the goal of the warning is to warn about non-portable code, not annoy
>> people.  Format specifiers and format string extensions covered by POSIX are
>> by definition portable on POSIX-compliant systems.  So I raise the question
>> of whether or not we should warn about these at all?
> 
> I agree that a good warning about non-portable code, that could be
> turned on by default or as part of -Wall, would be the ideal.
> 
> However, we're not there yet. In the meantime, I think having a
> warning under -pedantic that warns about non-ISO C format strings
> makes sense. I agree that it would be extremely annoying to warn about
> POSIX extensions by default, but under -pedantic I think users would
> expect to get warnings about these, just as with GCC.

Ok, I'm fine with this approach (putting under -pedantic), but should we put it under a separate warning group (that is activated by -Wformat-non-standard).  That way people could turn off these warnings if all the care about is POSIX compatibility by still keep the rest of the portability warnings.

> 
> Maybe the wording of the warnings and the name of the flag could be
> changed to make this intention more clear. I agree that just saying
> "non-standard" is a bit vague in the light of some of these features
> actually being standardized under POSIX.

I think improving the wording would help quite a bit.  What is "standard" is also a moving target, so saying what the "standard" is might help a great deal (e.g., C99).  It also may just add confusion.  Another way is to have -Wformat-posix-extensions, which is activated by -Wformat-non-standard (as I suggested above), and just have a parenthetical note in the warning that says "POSIX extension".

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