[RFC PATCH 0/3] Automatically convert configure options to meson build options

[Paolo Bonzini]

Right now meson_options.txt lists less than a dozen options, but about
40 more could come as configure tests are converted and moved to
meson.build.  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 passing unknown
--enable and --disable options to a Python program, and using
Meson's introspection support to match those to meson_options.txt

The disadvantages are:

- because we parse command-line options before meson is available,
the introspection output is stored in the source tree.  The output
is slightly modified using the "jq" tool in order to ensure that it's
stable and that modifications to meson_buildoptions.txt do not cause
horrible conflicts.  This is the main reason for the unattractive
diffstat (the number of JSON lines added is higher than the number
of configure lines removed, though of course the latter are code
that must be maintained manually and the former is not).

- we now need Python to generate the full help, so if Python is
missing we can only print a partial message and direct the user
to specify the interpreter with --python.  It would be possible to fix
this by rewriting the script in Perl (at least on Fedora, JSON::PP is
always installed if Perl is, because it's a dependency for CPAN; I'd
have to check Ubuntu and the BSDs), or if we want to write it as a
Bourne shell script, to further massage the introspection output into
for example TAB-separated values.

Opinions are welcome on whether this is worthwhile and how to solve
the above doubts.

Paolo

Paolo Bonzini (3):
  configure: quote command line arguments in config.status
  configure: early test for Python
  configure: automatically parse command line for meson -D options

 Makefile                                |   6 ++
 configure                               | 107 ++++++++-----------
 docs/devel/build-system.rst             |  35 +------
 meson-buildoptions.json                 | 130 ++++++++++++++++++++++++
 scripts/configure-parse-buildoptions.py |  94 +++++++++++++++++
 5 files changed, 280 insertions(+), 92 deletions(-)
 create mode 100644 meson-buildoptions.json
 create mode 100644 scripts/configure-parse-buildoptions.py

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2.26.2