[cfe-commits] [Patch] Warn about non-standard format strings (PR12017)

[Joerg Sonnenberger]

On Tue, Feb 21, 2012 at 09:57:23AM +0000, Hans Wennborg wrote:
> On Mon, Feb 20, 2012 at 21:00, Ted Kremenek <kremenek at apple.com> wrote:
> > On Feb 20, 2012, at 12:21 PM, Joerg Sonnenberger <joerg at britannica.bec.de>
> > wrote:
> >
> > There's "non-standard" and then there's completely unportable.  Warnings
> > like:
> >
> > +  // Combining 'L' with an integer conversion specifier.
> > +  printf("%Li", (long long)42); // expected-warning{{using the length
> > modifier 'L' with the conversion specifier 'i' is non-standard}}
> > +  printf("%Lo", (long long)42); // expected-warning{{using the length
> > modifier 'L' with the conversion specifier 'o' is non-standard}}
> >
> 
> [...]
> 
> > Do we really silently accept them?  Until very recently (a month ago?), we
> > emitted:
> >
> > t.c:4:12: warning: length modifier 'L' results in undefined behavior or no
> >       effect with 'i' conversion specifier [-Wformat]
> >   printf("%Li", (long long) 2);
> >           ~^~
> > 1 warning generated.
> >
> >
> > Now I see that TOT doesn't warn here.  Is this accepted somewhere?  I see no
> > test cases in clang/test that shows we should accept this.  Was this an
> > intentional change, or a regression?
> 
> r148859 made them accepted about a month ago. Looks intentional to me :)

Which brings up the question, where is that documented? At least the
Linux documentation is silent on this being valid.

Joerg