vs: Manually link generated .o files

Fixes #12550 .

VS automatically links CustomBuild outputs ending in .obj or .res,
but others need to be included explicitly.

mesonbuild/backend/vs2010backend.py

@@ -894,18 +894,6 @@ def add_include_dirs(self, lang, parent_node, file_inc_dirs):
         dirs = file_inc_dirs[lang]
         ET.SubElement(parent_node, "AdditionalIncludeDirectories").text = ';'.join(dirs)
 
-    @staticmethod
-    def has_objects(objects, additional_objects, generated_objects):
-        # Ignore generated objects, those are automatically used by MSBuild because they are part of
-        # the CustomBuild Outputs.
-        return len(objects) + len(additional_objects) > 0
-
-    @staticmethod
-    def add_generated_objects(node, generated_objects):
-        # Do not add generated objects to project file. Those are automatically used by MSBuild, because
-        # they are part of the CustomBuild Outputs.
-        return
-
     @staticmethod
     def escape_preprocessor_define(define: str) -> str:
         # See: https://msdn.microsoft.com/en-us/library/bb383819.aspx
@@ -1779,17 +1767,20 @@ def path_normalize_add(path, lis):
         for o in custom_objs:
             additional_objects.append(o)
 
+        # VS automatically links CustomBuild outputs whose name ends in .obj or .res,
+        # but the others need to be included explicitly
+        explicit_link_gen_objs = [obj for obj in gen_objs if not obj.endswith(('.obj', '.res'))]
+
         previous_objects = []
-        if self.has_objects(objects, additional_objects, gen_objs):
+        if len(objects) + len(additional_objects) + len(explicit_link_gen_objs) > 0:
             inc_objs = ET.SubElement(root, 'ItemGroup')
             for s in objects:
                 relpath = os.path.join(proj_to_build_root, s.rel_to_builddir(self.build_to_src))
                 if path_normalize_add(relpath, previous_objects):
                     ET.SubElement(inc_objs, 'Object', Include=relpath)
-            for s in additional_objects:
+            for s in additional_objects + explicit_link_gen_objs:
                 if path_normalize_add(s, previous_objects):
                     ET.SubElement(inc_objs, 'Object', Include=s)
-            self.add_generated_objects(inc_objs, gen_objs)
 
         ET.SubElement(root, 'Import', Project=r'$(VCTargetsPath)\Microsoft.Cpp.targets')
         self.add_regen_dependency(root)

test cases/common/52 object generator/meson.build

@@ -29,6 +29,14 @@ gen2 = generator(python,
  arguments : [comp, cc, '@INPUT@', '@OUTPUT0@'])
 generated2 = gen2.process(['source3.c'])
 
-e = executable('prog', 'prog.c', generated, generated2)
+# Generate an object file ending with .o even on Windows.
+# The VS backend needs to handle .o objects differently from .obj objects.
+gen3 = generator(python,
+ output : '@BASENAME@.o',
+ arguments : [comp, cc, '@INPUT@', '@OUTPUT@'])
+
+generated3 = gen3.process(['source4.c'])
+
+e = executable('prog', 'prog.c', generated, generated2, generated3)
 
 test('objgen', e)

test cases/common/52 object generator/prog.c

@@ -1,7 +1,8 @@
 int func1_in_obj(void);
 int func2_in_obj(void);
 int func3_in_obj(void);
+int func4_in_obj(void);
 
 int main(void) {
-    return func1_in_obj() + func2_in_obj() + func3_in_obj();
+    return func1_in_obj() + func2_in_obj() + func3_in_obj() + func4_in_obj();
 }

test cases/common/52 object generator/source4.c

@@ -0,0 +1,3 @@
+int func4_in_obj(void) {
+    return 0;
+}