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

[Peter Maydell]

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?

thanks
-- PMM