Re: [PATCH v3 3/5] configure: Clean up warning flag lists

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 6/17/20 6:37 AM, Richard Henderson wrote:
> Use a helper function to tidy the assembly of gcc_flags.
> Separate flags that disable warnings from those that enable,
> and sort the disable warnings to the end.
> 
> Suggested-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  configure | 42 ++++++++++++++++++++++++++++++++----------
>  1 file changed, 32 insertions(+), 10 deletions(-)
> 
> diff --git a/configure b/configure
> index b01b5e3bed..a8bef95282 100755
> --- a/configure
> +++ b/configure
> @@ -97,6 +97,11 @@ do_cxx() {
>      do_compiler "$cxx" "$@"
>  }
>  
> +# Append $2 to the variable named $1, with space separation
> +add_to() {
> +    eval $1=\${$1:+\"\$$1 \"}\$2
> +}

Nice trick Eric!

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> +
>  update_cxxflags() {
>      # Set QEMU_CXXFLAGS from QEMU_CFLAGS by filtering out those
>      # options which some versions of GCC's C++ compiler complain about
> @@ -2024,16 +2029,33 @@ if ! compile_prog "" "" ; then
>      error_exit "You need at least GCC v4.8 or Clang v3.4 (or XCode Clang v5.1)"
>  fi
>  
> -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-string-plus-int -Wno-typedef-redefinition $gcc_flags"
> -# Note that we do not add -Werror to gcc_flags here, because that would
> -# enable it for all configure tests. If a configure test failed due
> -# to -Werror this would just silently disable some features,
> -# so it's too error prone.
> +# Accumulate -Wfoo and -Wno-bar separately.
> +# We will list all of the enable flags first, and the disable flags second.
> +# Note that we do not add -Werror, because that would enable it for all
> +# configure tests. If a configure test failed due to -Werror this would
> +# just silently disable some features, so it's too error prone.
> +
> +warn_flags=
> +add_to warn_flags -Wold-style-declaration
> +add_to warn_flags -Wold-style-definition
> +add_to warn_flags -Wtype-limits
> +add_to warn_flags -Wformat-security
> +add_to warn_flags -Wformat-y2k
> +add_to warn_flags -Winit-self
> +add_to warn_flags -Wignored-qualifiers
> +add_to warn_flags -Wempty-body
> +add_to warn_flags -Wnested-externs
> +add_to warn_flags -Wendif-labels
> +add_to warn_flags -Wexpansion-to-defined
> +
> +nowarn_flags=
> +add_to nowarn_flags -Wno-initializer-overrides
> +add_to nowarn_flags -Wno-missing-include-dirs
> +add_to nowarn_flags -Wno-shift-negative-value
> +add_to nowarn_flags -Wno-string-plus-int
> +add_to nowarn_flags -Wno-typedef-redefinition
> +
> +gcc_flags="$warn_flags $nowarn_flags"
>  
>  cc_has_warning_flag() {
>      write_c_skeleton;
>