Re: [PATCHv2] sysdeps/ieee754/soft-fp: ignore maybe-uninitialized with -O [BZ #19444]

[Joseph Myers <joseph at codesourcery dot com>]

On Sun, 30 Sep 2018, Martin Jansa wrote:

> On Sun, Sep 30, 2018 at 04:53:36PM +0000, Joseph Myers wrote:
> > On Sun, 30 Sep 2018, Martin Jansa wrote:
> > 
> > > +#include <libc-diag.h>
> > > +/* R_f[01] are not set in cases where it is not used in packing, but the
> > > +   compiler does not see that it is set in all cases where it is
> > > +   used, resulting in warnings that it may be used uninitialized.
> > > +   The location of the warning differs in different versions of GCC,
> > > +   it may be where R is defined using a macro or it may be where the
> > > +   macro is defined.  */
> > 
> > This comment is missing the key information that it's specifically a 
> > warning seen with -O1.
> 
> The other 3 cases of the same:
> https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/ieee754/soft-fp/s_fma.c;h=41cf81a74bfc6a8c21c565fb04c90ced4bfd19e8;hb=refs/heads/master#l32
> https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/ieee754/soft-fp/s_fmaf.c;h=afe64356b3a9c5f3467c35b80f33ba946fbeee46;hb=refs/heads/master#l32
> https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/ieee754/soft-fp/s_fmal.c;h=4c2d4c5d9be09f0c8464fb20b81af3aff131e65d;hb=refs/heads/master#l32
> 
> are probably also triggered only with -O1, do you want me to update all
> 4 or just the new case?

They're definitely not limited to -O1 (or weren't when added in 2015, 
commit dc6b5aed1b406a53c4512d355376b4e12c7da971).  So it's only the new 
case for which a comment about being limited to -O1 is appropriate.

-- 
Joseph S. Myers
joseph@codesourcery.com