[libcamera-devel] [RFC PATCH] libcamera: Disable automatic vcs versioning

[Laurent Pinchart]

On Sat, Aug 20, 2022 at 03:29:48PM +0200, Christian Rauch via libcamera-devel wrote:
> Hi Tomi,
> 
> With the recent discussions on "versioning", I would actually argue that
> this should be removed entirely, and we should only rely on the semver
> versioning.

I'd rather not. It has been proven very useful multiple times to have
the exact git commit ID in bug reports. If we were to drop it, it would
increase our support burden. I'm fine omitting the commit ID when the
libcamera version exactly matches a released version, but not otherwise.

> Am 20.08.22 um 10:07 schrieb Tomi Valkeinen via libcamera-devel:
> > libcamera builds the git hash version into the libcamera library. This
> > makes ninja create the generated version.cpp on every build, and if the
> > git hash has changed, compilation of version.cpp and linking of
> > libcamera library.
> >
> > This patch adds a meson option to disable this behavior and instead use
> > the meson project-version as the version built into the library, which
> > is only generated at meson configuration time.
> >
> > With this change, ninja will nicely say "no work to do" if there's
> > nothing to compile, instead of starting the build and generating
> > version.cpp.

I'd prefer a way to skip recompilation (and relinking) if the version
hasn't changed since the last build.

> > But, more importantly, it often reduces build time. For example, this
> > takes a particular git range compilation (~20 py bindings patches) from
> > 43 seconds to 10 seconds. Obviously the improvement depends very much on
> > the patches in question. If every commit changes libcamera itself, there
> > is no difference.
> >
> > Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ideasonboard.com>
> > ---
> >  meson_options.txt         |  5 +++++
> >  src/libcamera/meson.build | 29 +++++++++++++++++++++--------
> >  2 files changed, 26 insertions(+), 8 deletions(-)
> >
> > diff --git a/meson_options.txt b/meson_options.txt
> > index 7a9aecfc..6a0bd0be 100644
> > --- a/meson_options.txt
> > +++ b/meson_options.txt
> > @@ -63,3 +63,8 @@ option('pycamera',
> >          type : 'feature',
> >          value : 'disabled',
> >          description : 'Enable libcamera Python bindings (experimental)')
> > +
> > +option('disable-vcs-versioning',
> > +        type : 'boolean',
> > +        value : false,
> > +        description : 'Disable automatic libcamera library versioning with the git hash')
> > diff --git a/src/libcamera/meson.build b/src/libcamera/meson.build
> > index ce1f0f2f..6fd6f084 100644
> > --- a/src/libcamera/meson.build
> > +++ b/src/libcamera/meson.build
> > @@ -121,14 +121,27 @@ endforeach
> >
> >  libcamera_sources += control_sources
> >
> > -gen_version = meson.project_source_root() / 'utils' / 'gen-version.sh'
> > -
> > -# Use vcs_tag() and not configure_file() or run_command(), to ensure that the
> > -# version gets updated with every ninja build and not just at meson setup time.
> > -version_cpp = vcs_tag(command : [gen_version, meson.project_build_root(), meson.project_source_root()],
> > -                      input : 'version.cpp.in',
> > -                      output : 'version.cpp',
> > -                      fallback : meson.project_version())
> > +if get_option('disable-vcs-versioning')
> > +    cdata = configuration_data()
> > +    cdata.set('VCS_TAG', meson.project_version())
> > +
> > +    # For some reason using 'version.cpp' as output file works fine for generation
> > +    # but causes meson to delete the file before build. Any other file name
> > +    # seems to work.
> > +    version_cpp = configure_file(input : 'version.cpp.in',
> > +                                 output : 'version_static.cpp',
> > +                                 configuration : cdata)
> > +
> > +else
> > +    gen_version = meson.project_source_root() / 'utils' / 'gen-version.sh'
> > +
> > +    # Use vcs_tag() and not configure_file() or run_command(), to ensure that the
> > +    # version gets updated with every ninja build and not just at meson setup time.
> > +    version_cpp = vcs_tag(command : [gen_version, meson.project_build_root(), meson.project_source_root()],
> > +                          input : 'version.cpp.in',
> > +                          output : 'version.cpp',
> > +                          fallback : meson.project_version())
> > +endif
> >
> >  libcamera_sources += version_cpp
> >

-- 
Regards,

Laurent Pinchart