[cfe-commits] r148859 - in /cfe/trunk: lib/Analysis/FormatString.cpp lib/Analysis/PrintfFormatString.cpp lib/Analysis/ScanfFormatString.cpp test/Sema/format-strings-scanf.c test/Sema/format-strings.c

[Ted Kremenek]

Agreed.  We could even have -Wformat-gnu on by default for certain targets where the GNU extensions were known to be supported. 

There is a larger issue, however, that some format specifiers may only make sense for certain functions and not others, even on the same target.  Having a separate warning flag doesn't actually help here.  Instead, we need a way to distinguish functions by the grouping of format specifiers that they accept.  I don't have clear design in my head on how to do this, either than extending the existing 'format' attributes. 


On Tuesday, January 24, 2012 at 3:43 PM, Chandler Carruth wrote:

> If you would like to contribute a -Wformat-gnu set of warnings which flag use of format specifiers that are GNU extensions, I think that would be a very useful warning for Clang to have.
> 
> On Tue, Jan 24, 2012 at 3:15 PM, Joerg Sonnenberger <joerg at britannica.bec.de (mailto:joerg at britannica.bec.de)> wrote:
> > The problem is that it is about shutting up warnings for Linux (or OSX)
> > specific code and at the same time stopping the warning for everyone
> > else on code that needs them.
> We can't have it both ways though. We have to pick one behavior to be the default, and currently the largest users of Clang are on OSX or Linux and thus benefit from the default behavior you are observing. It's not a great way to choose a default, but neither is making warn by default for the majority of its users on code that is correct. =/ Again, I'm not really thrilled about it, but it seems pragmatic. It is at least consistent with -Wgnu and other extensions in Clang. 
> 
> I don't think its too onerous to have to pass -Wformat-gnu to get more detailed warnings, any more than some folks pass -Wgnu to find out about language extensions in use.
> 
> While it might be possible to make -Wformat include -Wformat-gnu when not compiling in one af the '-std=gnu*' language dialect variations, that would seem a really confusing bit of behavior. I like warning flags being simple set arithmetic. 
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