backend: always use the same code to compute the files in ExtractedObjects

Instead of asking the ExtractedObjects, but with a hook back into the backend,
use the existing function in the backend itself.  This fixes using the
extract_objects(...) of a generated source file in a custom_target.

It should also fix recursive extract_all_objects with the Xcode backend.

Fixes: #10394

mesonbuild/backend/backends.py

@@ -456,6 +456,10 @@ class Backend:
         obj_list = self._flatten_object_list(target, target.get_objects(), proj_dir_to_build_root)
         return list(dict.fromkeys(obj_list))
 
+    def determine_ext_objs(self, objects: build.ExtractedObjects, proj_dir_to_build_root: str = '') -> T.List[str]:
+        obj_list = self._flatten_object_list(objects.target, [objects], proj_dir_to_build_root)
+        return list(dict.fromkeys(obj_list))
+
     def _flatten_object_list(self, target: build.BuildTarget,
                              objects: T.Sequence[T.Union[str, 'File', build.ExtractedObjects]],
                              proj_dir_to_build_root: str) -> T.List[str]:
@@ -477,7 +481,7 @@ class Backend:
             elif isinstance(obj, build.ExtractedObjects):
                 if obj.recursive:
                     obj_list += self._flatten_object_list(obj.target, obj.objlist, proj_dir_to_build_root)
-                obj_list += self.determine_ext_objs(obj, proj_dir_to_build_root)
+                obj_list += self._determine_ext_objs(obj, proj_dir_to_build_root)
             else:
                 raise MesonException('Unknown data type in object list.')
         return obj_list
@@ -808,7 +812,7 @@ class Backend:
         machine = self.environment.machines[target.for_machine]
         return self.canonicalize_filename(gen_source) + '.' + machine.get_object_suffix()
 
-    def determine_ext_objs(self, extobj: 'build.ExtractedObjects', proj_dir_to_build_root: str) -> T.List[str]:
+    def _determine_ext_objs(self, extobj: 'build.ExtractedObjects', proj_dir_to_build_root: str) -> T.List[str]:
         result: T.List[str] = []
 
         # Merge sources and generated sources
@@ -1297,8 +1301,7 @@ class Backend:
             elif isinstance(i, build.GeneratedList):
                 fname = [os.path.join(self.get_target_private_dir(target), p) for p in i.get_outputs()]
             elif isinstance(i, build.ExtractedObjects):
-                outputs = i.get_outputs(self)
-                fname = self.get_extracted_obj_paths(i.target, outputs)
+                fname = self.determine_ext_objs(i)
             elif isinstance(i, programs.ExternalProgram):
                 assert i.found(), "This shouldn't be possible"
                 assert i.path is not None, 'for mypy'
@@ -1310,9 +1313,6 @@ class Backend:
             srcs += fname
         return srcs
 
-    def get_extracted_obj_paths(self, target: build.BuildTarget, outputs: T.List[str]) -> T.List[str]:
-        return [os.path.join(self.get_target_private_dir(target), p) for p in outputs]
-
     def get_custom_target_depend_files(self, target: build.CustomTarget, absolute_paths: bool = False) -> T.List[str]:
         deps: T.List[str] = []
         for i in target.depend_files:

mesonbuild/backend/xcodebackend.py

@@ -259,9 +259,6 @@ class XCodeBackend(backends.Backend):
         obj_path = f'{project}.build/{buildtype}/{tname}.build/Objects-normal/{arch}/{stem}.o'
         return obj_path
 
-    def get_extracted_obj_paths(self, target: build.BuildTarget, outputs: T.List[str]) -> T.List[str]:
-        return outputs
-
     def generate(self):
         self.serialize_tests()
         # Cache the result as the method rebuilds the array every time it is called.
@@ -1469,7 +1466,7 @@ class XCodeBackend(backends.Backend):
                 # Add extracted objects to the link line by hand.
                 if isinstance(o, build.ExtractedObjects):
                     added_objs = set()
-                    for objname_rel in o.get_outputs(self):
+                    for objname_rel in self.determine_ext_objs(o):
                         objname_abs = os.path.join(self.environment.get_build_dir(), o.target.subdir, objname_rel)
                         if objname_abs not in added_objs:
                             added_objs.add(objname_abs)

mesonbuild/build.py

@@ -447,12 +447,6 @@ class ExtractedObjects(HoldableObject):
                                      'in Unity builds. You can only extract all '
                                      'the object files for each compiler at once.')
 
-    def get_outputs(self, backend: 'Backend') -> T.List[str]:
-        return [
-            backend.object_filename_from_source(self.target, source)
-            for source in self.get_sources(self.srclist, self.genlist)
-        ]
-
 
 @dataclass(eq=False, order=False)
 class StructuredSources(HoldableObject):
@@ -2878,7 +2872,7 @@ def get_sources_string_names(sources, backend):
         elif isinstance(s, (BuildTarget, CustomTarget, CustomTargetIndex, GeneratedList)):
             names += s.get_outputs()
         elif isinstance(s, ExtractedObjects):
-            names += s.get_outputs(backend)
+            names += backend.determine_ext_objs(s)
         elif isinstance(s, File):
             names.append(s.fname)
         else: