gh-153903: Fix ctypes wrap_dll_function() with string annotations (#154042)

Call get_annotations() with eval_str=True.

Author: vstinner

Lib/ctypes/util.py

@@ -579,7 +579,7 @@ def wrap_dll_function(dll):
     def decorator(func):
         name = func.__name__
         ptr = getattr(dll, name)
-        annotations = annotationlib.get_annotations(func)
+        annotations = annotationlib.get_annotations(func, eval_str=True)
 
         try:
             restype = annotations.pop("return")

Lib/test/test_ctypes/test_funcptr.py

@@ -151,6 +151,11 @@ def noexist():
             def PyObject_GetAttrString(op: ctypes.py_object, attr: ctypes.c_char_p):
                 pass
 
+    def test_wrap_dll_function_str_ann(self):
+        from test.test_ctypes import wrap_str_ann
+        version = wrap_str_ann.Py_GetVersion()
+        self.assertIsInstance(version, bytes)
+
 
 if __name__ == '__main__':
     unittest.main()

Lib/test/test_ctypes/wrap_str_ann.py

@@ -0,0 +1,13 @@
+from __future__ import annotations
+import ctypes.util
+
+def test_ann() -> ctypes.c_char_p:
+    ...
+
+# Check that "from __future__ import annotations" works as expected
+if not isinstance(test_ann.__annotations__['return'], str):
+    raise Exception("annotations must be strings")
+
+@ctypes.util.wrap_dll_function(ctypes.pythonapi)
+def Py_GetVersion() -> ctypes.c_char_p:
+    ...