clang: Always pass POSIX paths to consumers

Fixes #12191

Author: amyspark

mesonbuild/backend/backends.py

@@ -309,10 +309,10 @@ def get_target_filename(self, t: T.Union[build.Target, build.CustomTargetIndex],
         else:
             assert isinstance(t, build.BuildTarget), t
             filename = t.get_filename()
-        return os.path.join(self.get_target_dir(t), filename)
+        return (Path(self.get_target_dir(t)) / filename).as_posix()
 
     def get_target_filename_abs(self, target: T.Union[build.Target, build.CustomTargetIndex]) -> str:
-        return os.path.join(self.environment.get_build_dir(), self.get_target_filename(target))
+        return (Path(self.environment.get_build_dir()) / self.get_target_filename(target)).as_posix()
 
     def get_source_dir_include_args(self, target: build.BuildTarget, compiler: 'Compiler', *, absolute_path: bool = False) -> T.List[str]:
         curdir = target.get_subdir()
@@ -339,16 +339,16 @@ def get_target_filename_for_linking(self, target: T.Union[build.Target, build.Cu
         # On all other platforms, we link to the library directly.
         if isinstance(target, build.SharedLibrary):
             link_lib = target.get_import_filename() or target.get_filename()
-            return os.path.join(self.get_target_dir(target), link_lib)
+            return (Path(self.get_target_dir(target)) / link_lib).as_posix()
         elif isinstance(target, build.StaticLibrary):
-            return os.path.join(self.get_target_dir(target), target.get_filename())
+            return (Path(self.get_target_dir(target)) / target.get_filename()).as_posix()
         elif isinstance(target, (build.CustomTarget, build.CustomTargetIndex)):
             if not target.is_linkable_target():
                 raise MesonException(f'Tried to link against custom target "{target.name}", which is not linkable.')
-            return os.path.join(self.get_target_dir(target), target.get_filename())
+            return (Path(self.get_target_dir(target)) / target.get_filename()).as_posix()
         elif isinstance(target, build.Executable):
             if target.import_filename:
-                return os.path.join(self.get_target_dir(target), target.get_import_filename())
+                return (Path(self.get_target_dir(target)) / target.import_filename).as_posix()
             else:
                 return None
         raise AssertionError(f'BUG: Tried to link to {target!r} which is not linkable')

mesonbuild/backend/ninjabackend.py

@@ -3222,7 +3222,7 @@ def generate_pch(self, target, header_deps=None):
     def get_target_shsym_filename(self, target):
         # Always name the .symbols file after the primary build output because it always exists
         targetdir = self.get_target_private_dir(target)
-        return os.path.join(targetdir, target.get_filename() + '.symbols')
+        return (Path(targetdir) / (target.get_filename() + '.symbols')).as_posix()
 
     def generate_shsym(self, target):
         target_file = self.get_target_filename(target)
@@ -3235,7 +3235,7 @@ def generate_shsym(self, target):
         self.add_build(elem)
 
     def get_import_filename(self, target):
-        return os.path.join(self.get_target_dir(target), target.import_filename)
+        return (Path(self.get_target_dir(target)) / target.import_filename).as_posix()
 
     def get_target_type_link_args(self, target, linker):
         commands = []

mesonbuild/compilers/mixins/clang.py

@@ -121,6 +121,13 @@ def openmp_flags(self) -> T.List[str]:
             # Shouldn't work, but it'll be checked explicitly in the OpenMP dependency.
             return []
 
+    def gen_vs_module_defs_args(self, defsfile: str) -> T.List[str]:
+        if isinstance(self.linker, (MSVCDynamicLinker)):
+            # With MSVC, DLLs only export symbols that are explicitly exported,
+            # so if a module defs file is specified, we use that to export symbols
+            return ['-Wl,/DEF:' + defsfile]
+        return super().gen_vs_module_defs_args(defsfile)
+
     @classmethod
     def use_linker_args(cls, linker: str, version: str) -> T.List[str]:
         # Clang additionally can use a linker specified as a path, which GCC