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

3 files changed, 15 insertions, 0 deletions

diff --git a/test cases/failing/78 link with shared module on osx/meson.build b/test cases/failing/78 link with shared module on osx/meson.build
new file mode 100644
index 000000000..2c714f97a
--- /dev/null
+++ b/test cases/failing/78 link with shared module on osx/meson.build
@@ -0,0 +1,8 @@
+project('link with shared module', 'c')
+
+if host_machine.system() != 'darwin'
+  error('Test only fails on OSX')
+endif
+
+m = shared_module('mymodule', 'module.c')
+e = executable('prog', 'prog.c', link_with : m)
diff --git a/test cases/failing/78 link with shared module on osx/module.c b/test cases/failing/78 link with shared module on osx/module.c
new file mode 100644
index 000000000..81b0d5af0
--- /dev/null
+++ b/test cases/failing/78 link with shared module on osx/module.c
@@ -0,0 +1,3 @@
+int func(void) {
+    return 1496;
+}
diff --git a/test cases/failing/78 link with shared module on osx/prog.c b/test cases/failing/78 link with shared module on osx/prog.c
new file mode 100644
index 000000000..8164d8da1
--- /dev/null
+++ b/test cases/failing/78 link with shared module on osx/prog.c
@@ -0,0 +1,4 @@
+
+int main(int argc, char **argv) {
+    return func();
+}