Re: [PATCH v2 24/24] configure: automatically parse command line for meson -D options

[Thomas Huth]

On 12/10/2021 13.13, Paolo Bonzini wrote:
> Right now meson_options.txt lists about 90 options.  Each option
> needs code in configure to parse it and pass the option down to Meson as
> a -D command-line argument; in addition the default must be duplicated
> between configure and meson_options.txt.  This series tries to remove
> the code duplication by generating the case statement for those --enable
> and --disable options, as well as the corresponding help text.
>
> About 80% of the options can be handled completely by the new mechanism.
> Eight meson options are not of the --enable/--disable kind.  Six more need
> to be parsed in configure for various reasons documented in the patch,
> but they still have their help automatically generated.
>
> The advantages are:
>
> - less code in configure
>
> - parsing and help is more consistent (for example --enable-blobs was
>    not supported)
>
> - options are described entirely in one place, meson_options.txt.
>    This make it more attractive to use Meson options instead of
>    hand-crafted configure options and config-host.mak
>
> A few options change name: --enable-tcmalloc and --enable-jemalloc
> become --enable-malloc={tcmalloc,jemalloc}; --disable-blobs becomes
> --disable-install-blobs; --enable-trace-backend becomes
> --enable-trace-backends.

... and you provide compatibility wrappers now - maybe worth to mention it here.

...
> @@ -1793,18 +1427,12 @@ Advanced options (experts only):
>                              (by default affects only QEMU, not tools like 
> qemu-img)
>     --enable-block-drv-whitelist-in-tools
>                              use block whitelist also in tools instead of only 
> QEMU
> -  --enable-trace-backends=B Set trace backend
> -                           Available backends: $trace_backend_list

Old output with --help:

 --enable-trace-backend=B Set trace backend
                           Available backends: nop, dtrace, ftrace, simple, 
stderr, ust

New output:

  --enable-trace-backends=CHOICE
                           Set available tracing backends [log]

Why does it fail to list the choices here? ... it works for the other
options like "--enable-malloc"?

 Thomas