[PATCH] meson: Don't build tests when CLang lacks -fsemantic-interposition

[Martin Kletzander]

On Tue, Mar 21, 2023 at 05:47:19PM +0100, Michal Privoznik wrote:
>There are some CLang versions that do not support
>-fsemantic-interposition. If that's the case, the code is
>optimized so much that our mocking no longer works.
>
>Therefore, disable tests and produce a warning.
>
>Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>---
>
>Technically, this is a v2 of:
>
>https://listman.redhat.com/archives/libvir-list/2023-March/238943.html
>
>but a different approach is implemented, so I'm sending it anew.
>
> meson.build | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
>diff --git a/meson.build b/meson.build
>index a0682e8d0b..c15003ce02 100644
>--- a/meson.build
>+++ b/meson.build
>@@ -2035,8 +2035,18 @@ subdir('src')
>
> subdir('tools')
>
>-build_tests = not get_option('tests').disabled()
>-if build_tests
>+build_tests = [ not get_option('tests').disabled() ]
>+if build_tests[0] and \
>+   cc.get_id() == 'clang' and \
>+   not supported_cc_flags.contains('-fsemantic-interposition') \
>+   and get_option('optimization') != '0'
>+   # If CLang doesn't support -fsemantic-interposition then our
>+   # mocking doesn't work. The best we can do is to not run the
>+   # test suite.
>+   build_tests = [ false, '!!! Forcibly disabling tests because CLang lacks -fsemantic-interposition. Update CLang or disable optimization !!!' ]
>+endif
>+

So at first I wanted to suggest something like:

if cc.get_id() == 'clang' and \
    not supported_cc_flags.contains('-fsemantic-interposition') \
    and get_option('optimization') != '0'
   # If CLang doesn't support -fsemantic-interposition then our
   # mocking doesn't work. The best we can do is to not run the
   # test suite.
   if get_option('tests').enabled()
     error('Cannot enable tests because CLang lacks -fsemantic-interposition. Update CLang or disable optimization')
   else
     build_tests = false
   endif
else
   build_tests = not get_option('tests').disabled()
endif

Which would simply error out if you want the tests to be enabled on such
system.  However that has the downside that some potential contributor
might not notice the tests are being disabled and we would also have to
have another place where to track the enablement of tests/optimization,
in our CI.  It is possible, but after some tries I think your approach
is better and the main thing is that we need something to be pushed in
order for us not to get into failing CI fatigue which I've seen in other
projects where CI failures are just being dismissed after couple of
issues.  So:

Reviewed-by: Martin Kletzander <mkletzan at redhat.com>

>+if build_tests[0]
>   subdir('tests')
> endif
>
>-- 
>2.39.2
>
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