On Thu, Jan 10, 2019 at 10:54:46AM -0800, Nick Desaulniers wrote:
> On Wed, Jan 9, 2019 at 8:22 PM Nathan Chancellor
> <natechancel...@gmail.com> wrote:
> >
> > Clang warns:
> >
> > In file included from drivers/net/ethernet/intel/iavf/iavf_main.c:4:
> > In file included from drivers/net/ethernet/intel/iavf/iavf.h:37:
> > In file included from drivers/net/ethernet/intel/iavf/iavf_type.h:8:
> > drivers/net/ethernet/intel/iavf/iavf_osdep.h:49:18: warning: 'format'
> > attribute argument not supported: gnu_printf [-Wignored-attributes]
> > __attribute__ ((format(gnu_printf, 3, 4)));
> > ^
> > 1 warning generated.
> >
> > We can convert from gnu_printf to printf without any side effects for
> > two reasons:
> >
> > 1. All iavf_debug instances use standard printf formats, as pointed out
> > by Miguel Ojeda at the below link, meaning gnu_printf is not strictly
> > required.
> >
> > 2. However, GCC has aliased printf to gnu_printf on Linux since at least
> > 2010 based on git history.
>
> Thanks for this fix!
> FWIW, using godbolt to see which version something was added in is
> better than giving a year of the commit. I don't think it matters for
> this case, as the kernel already makes use of `printf` as you do in
> this change, but food for thought for next time.
>
Yes that is a good point, I need to be taking advantage of that site
more.
Thank you for the review!
Nathan
> >
> > From gcc/c-family/c-format.c:
> >
> > /* Attributes such as "printf" are equivalent to those such as
> > "gnu_printf" unless this is overridden by a target. */
> > static const target_ovr_attr gnu_target_overrides_format_attributes[] =
> > {
> > { "gnu_printf", "printf" },
> > { "gnu_scanf", "scanf" },
> > { "gnu_strftime", "strftime" },
> > { "gnu_strfmon", "strfmon" },
> > { NULL, NULL }
> > };
> >
> > The mentioned override only happens on Windows (mingw32). Changing from
> > gnu_printf to printf is a no-op for GCC and stops Clang from warning.
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/111
> > Suggested-by: Miguel Ojeda <miguel.ojeda.sando...@gmail.com>
> > Signed-off-by: Nathan Chancellor <natechancel...@gmail.com>
> > ---
> > drivers/net/ethernet/intel/iavf/iavf_osdep.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/intel/iavf/iavf_osdep.h
> > b/drivers/net/ethernet/intel/iavf/iavf_osdep.h
> > index e6e0b0328706..c90cafb526d0 100644
> > --- a/drivers/net/ethernet/intel/iavf/iavf_osdep.h
> > +++ b/drivers/net/ethernet/intel/iavf/iavf_osdep.h
> > @@ -46,7 +46,7 @@ struct iavf_virt_mem {
> >
> > #define iavf_debug(h, m, s, ...) iavf_debug_d(h, m, s, ##__VA_ARGS__)
> > extern void iavf_debug_d(void *hw, u32 mask, char *fmt_str, ...)
> > - __attribute__ ((format(gnu_printf, 3, 4)));
> > + __printf(3, 4);
>
> And you make use of the __attribute__ wrapper from
> include/linux/compiler_attributes.h, cool.
> Reviewed-by: Nick Desaulniers <ndesaulni...@google.com>
>
> --
> Thanks,
> ~Nick Desaulniers
