backends: include objects of linked targets into the depscan phase

The get_all_linked_targets() method is incomplete, in that it does
not check other targets that provide objects for the target. While
ninjabackend.py does use `flatten_object_list` on the target itself,
it does not check any link_with or link_whole targets. And because the
static library in a `BothLibraries` object might actually have no sources
and have just an `ExtractedObjects` entry instead, using `link_with:
foo.get_static_lib()` in a Fortran program is broken.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

mesonbuild/backend/backends.py

@@ -508,14 +508,21 @@ class Backend:
     def get_all_linked_targets(self, target: build.BuildTarget) -> T.Iterator[build.BuildTargetTypes]:
         """Get all targets that have been linked with this one, including internal and
         indirect static libraries unlike :method:`build.BuildTarget.get_all_link_deps`
-        and :method:`build.all_dependencies_recurse`.
+        and :method:`build.all_dependencies_recurse`, and targets whose objects
+        are borrowed by this one or any returned target.
 
         This is useful for cases where we need to analyze these links, such as
         for module information.
         """
         seen: T.Set[build.BuildTarget] = set()
-
         stack: T.Deque[build.BuildTargetTypes] = deque()
+
+        def add_linked_targets(t: build.BuildTarget) -> None:
+            stack.extendleft(t.link_targets)
+            stack.extendleft(t.link_whole_targets)
+            _, od = self.flatten_object_list(t)
+            stack.extendleft(od)
+
         stack.extendleft(target.link_targets)
         stack.extendleft(target.link_whole_targets)
         while stack:
@@ -523,8 +530,7 @@ class Backend:
             if t in seen or not isinstance(t, build.BuildTarget):
                 continue
             seen.add(t)
-            stack.extendleft(t.link_targets)
-            stack.extendleft(t.link_whole_targets)
+            add_linked_targets(t)
             yield t
         assert target not in seen, 'should not have self'
 

test cases/fortran/24 both_libraries/main.f90

@@ -0,0 +1,5 @@
+program main
+  use mymod, only: myval
+  implicit none
+  print *, myval
+end program main

test cases/fortran/24 both_libraries/meson.build

@@ -0,0 +1,6 @@
+project('fmodbug', 'fortran', default_options: ['default_library=both'])
+
+lib = library('mylib', 'modsrc.f90')
+# CI also runs with other default_library settings
+lib_linked = get_option('default_library') == 'both' ? lib.get_static_lib() : lib
+exe = executable('myexe', 'main.f90', link_with: lib_linked)

test cases/fortran/24 both_libraries/modsrc.f90

@@ -0,0 +1,4 @@
+module mymod
+  implicit none
+  integer, parameter :: myval = 42
+end module mymod