Re: [PATCH v3] meson: disable PCRE2 dependency by default in macOS

[Patrick Steinhardt <ps@pks.im>]

On Mon, Jul 14, 2025 at 09:55:27PM -0400, Eli Schwartz wrote:
> On 7/13/25 1:48 PM, Carlo Marcelo Arenas Belón wrote:
> > diff --git a/meson.build b/meson.build
> > index 7fea4a34d6..e1475be6c8 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -1055,7 +1055,8 @@ else
> >    build_options_config.set('NO_ICONV', '1')
> >  endif
> >  
> > -pcre2 = dependency('libpcre2-8', required: get_option('pcre2'), default_options: ['default_library=static', 'test=false'])
> > +pcre2_feature = get_option('pcre2').disable_auto_if(host_machine.system() == 'darwin' and not get_option('macos_workaround_system_pcre2'))
> > +pcre2 = dependency('libpcre2-8', required: pcre2_feature, default_options: ['default_library=static', 'test=false'])
> >  if pcre2.found()
> >    libgit_dependencies += pcre2
> >    libgit_c_args += '-DUSE_LIBPCRE2'
> 
> 
> Instead of disable_auto_if, we should simply verify a working install.
> 
> if pcre2.found() and pcre2.type_name() != 'internal' and
> host_machine.system() == 'darwin'
>     # macOS installs a broken system package, double check
>     if not compiler.has_header('pcre2.h', dependencies: pcre2)
>         if get_option('pcre2').enabled()
>             error('broken pcre2 install found but pcre2 is required')
>         endif
>         # Replace with not-found-dependency
>         pcre2 = dependency('', required: false)
>         warning('broken pcre2 install found, disabling pcre2 feature')

Okay. So if the `pcre2` feature was explicitly enabled we error out and
abort, otherwise we print a warning and disable it. This makes a lot of
sense to me.

>     endif
> endif
> 
> if pcre2.found()
>     libgit_dependencies += pcre2
> 
> [...]
> 
> 
> Please double-check my work, that this compiler.has_header() is
> sufficient on your reproducer system to detect and disable the
> non-working feature.

I think auto-detecting such broken PCRE2 libraries is indeed the best
way forward, thanks!

> > diff --git a/meson_options.txt b/meson_options.txt
> > index e7f768df24..f63ff32556 100644
> > --- a/meson_options.txt
> > +++ b/meson_options.txt
> > @@ -45,7 +45,7 @@ option('gitweb', type: 'feature', value: 'auto',
> >    description: 'Build Git web interface. Requires Perl.')
> >  option('iconv', type: 'feature', value: 'auto',
> >    description: 'Support reencoding strings with different encodings.')
> > -option('pcre2', type: 'feature', value: 'enabled',
> > +option('pcre2', type: 'feature', value: 'auto',
> 
> 
> This part is fine. We shouldn't default-fail if it isn't found, when we
> can't expect it to be universally available.

Agreed. I guess tha only reason why I picked "enabled" here is because
we also got a wrapper in "subprojects/". But with this new workaround in
place I agree that it is sensible to switch to "auto".

Patrick