Re: [PATCH v1 3/6] configure: add --without-default-features

[Paolo Bonzini <pbonzini@redhat.com>]

On 09/12/20 18:00, Alex Bennée wrote:
> By default QEMU enables a lot of features if it can probe and find the
> support libraries. It also enables a bunch of features by default.
> This patch adds the ability to build --without-default-features which
> can be paired with a --without-default-devices for a barely functional
> build.
> 
> The main use case for this is testing our build assumptions and for
> minimising the amount of stuff you build if you just want to test a
> particular feature on your relatively slow emulated test system.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>   configure | 159 ++++++++++++++++++++++++++++++------------------------
>   1 file changed, 88 insertions(+), 71 deletions(-)
> 
> diff --git a/configure b/configure
> index 8f2095a2db..a08e6c96e0 100755
> --- a/configure
> +++ b/configure
> @@ -291,10 +291,24 @@ unset target_list_exclude
>   #
>   # Always add --enable-foo and --disable-foo command line args.
>   # Distributions want to ensure that several features are compiled in, and it
> -# is impossible without a --enable-foo that exits if a feature is not found.
> +# is impossible without a --enable-foo that exits if a feature is not
> +# found.
>   
> -brlapi=""
> -curl=""
> +default_feature=""
> +default_yes_feature="yes"
> +# parse CC options second
> +for opt do
> +  optarg=$(expr "x$opt" : 'x[^=]*=\(.*\)')
> +  case "$opt" in
> +      --without-default-features)
> +          default_feature="no"
> +          default_yes_feature="no"

default_yes_features can be replaced with ${default_feature:-yes} if you 
wish.

> +  ;;
> +  esac
> +done

Since Meson has equivalent functionality to --without-default-features, 
you also want to add -Dauto_features=disabled to the meson command line.

Also, the gettext feature is true/false/empty rather than yes/no, so 
it's not being adjusted.  I suggest you change it (in meson_options.txt) 
from "boolean" to "feature" (auto/enabled/disabled) and move the 
detection code from configure to po/meson.build.  It should be as simple as

-if get_option('gettext')
+if find_program('xgettext', required: get_option('gettext')).found()

and then it will also get the functionality from -Dauto_features.

Paolo

> @@ -453,7 +467,7 @@ gettext=""
>   bogus_os="no"
>   malloc_trim="auto"
>   
> -# parse CC options first
> +# parse CC options second
>   for opt do
>     optarg=$(expr "x$opt" : 'x[^=]*=\(.*\)')
>     case "$opt" in
> @@ -796,7 +810,7 @@ Linux)
>     audio_possible_drivers="oss alsa sdl pa"
>     linux="yes"
>     linux_user="yes"
> -  vhost_user="yes"
> +  vhost_user="$default_yes_feature"
>   ;;
>   esac
>   
> @@ -940,6 +954,8 @@ for opt do
>     ;;
>     --without-default-devices) default_devices="no"
>     ;;
> +  --without-default-features) # processed above
> +  ;;
>     --enable-gprof) gprof="yes"
>     ;;
>     --enable-gcov) gcov="yes"
> @@ -1737,7 +1753,8 @@ Advanced options (experts only):
>     --gdb=GDB-path           gdb to use for gdbstub tests [$gdb_bin]
>   
>   Optional features, enabled with --enable-FEATURE and
> -disabled with --disable-FEATURE, default is enabled if available:
> +disabled with --disable-FEATURE, default is enabled if available
> +(unless built with --without-default-features):
>   
>     system          all system emulation targets
>     user            supported user emulation targets
>