More clearly explain portability issues with linking to a module

Refine #3277

According to what I read on the internet, on OSX, both MH_BUNDLE (module)
and MH_DYLIB (shared library) can be dynamically loaded using dlopen(), but
it is not possible to link against MH_BUNDLE as if they were shared
libraries.

Metion this as an issue in the documentation.

Emitting a warning, and then going on to fail during the build with
mysterious errors in symbolextractor isn't very helpful, so make attempting
this an error on OSX.

Add a test for that.

See also:
https://docstore.mik.ua/orelly/unix3/mac/ch05_03.htm
https://stackoverflow.com/questions/2339679/what-are-the-differences-between-so-and-dylib-on-osx

1 files changed, 6 insertions, 2 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 4b42365..36e2e3c 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -1086,8 +1086,12 @@ You probably should put it in link_with instead.''')
         '''
         for link_target in self.link_targets:
             if isinstance(link_target, SharedModule):
-                mlog.warning('''target links against shared modules. This is not
-recommended as it can lead to undefined behaviour on some platforms''')
+                if for_darwin(self.is_cross, self.environment):
+                    raise MesonException('''target links against shared modules.
+This is not permitted on OSX''')
+                else:
+                    mlog.warning('''target links against shared modules. This is not
+recommended as it is not supported on some platforms''')
                 return
 
 class Generator: