Re: [Qemu-devel] [RFC PATCH for 2.10 33/35] configure: clang does not support -Wexpansion-to-defined

[Philippe Mathieu-Daudé]

On 07/24/2017 06:22 PM, Peter Maydell wrote:
> On 24 July 2017 at 19:27, Philippe Mathieu-Daudé <address@hidden> wrote:
> > Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> > ---
> >   configure | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/configure b/configure
> > index 6b52e19ee3..48295aa1e6 100755
> > --- a/configure
> > +++ b/configure
> > @@ -1582,8 +1582,12 @@ gcc_flags="-Wold-style-declaration -Wold-style-definition 
> > -Wtype-limits"
> >   gcc_flags="-Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers 
> > $gcc_flags"
> >   gcc_flags="-Wno-missing-include-dirs -Wempty-body -Wnested-externs $gcc_flags"
> >   gcc_flags="-Wendif-labels -Wno-shift-negative-value $gcc_flags"
> > -gcc_flags="-Wno-initializer-overrides -Wexpansion-to-defined $gcc_flags"
> > +gcc_flags="-Wno-initializer-overrides $gcc_flags"
> >   gcc_flags="-Wno-string-plus-int $gcc_flags"
> > +# clang does not support -Wexpansion-to-defined
> > +if ! echo | $cc -dM -E - | grep __clang__ > /dev/null 2>&1 ; then
> > +    gcc_flags="-Wexpansion-to-defined $gcc_flags"
> > +fi
>
> We already have a mechanism for testing that the warning
> flags we pass here are actually supported by the compiler
> (the cc_has_warning_flag() function, which we run on
> every flag in $gcc_flags). Why does -Wexpansion-to-defined
> need special casing?

Yeah no idea, it works with clang 3.9 but not 5.0, I didn't investigate 
further. I prefixed this patch 'RFC' to not consider it but provide it 
if someone wanted to reproduce the analysis. Maybe I should prefix it 
'XXX' next time or 'NOT FOR MERGE'.

Regards,

Phil.