Raise on unsupported platforms in GetPyRuntimeAddress

Author: lkollar

Lib/test/test_external_inspection.py

@@ -997,5 +997,20 @@ def main_work():
                          "GIL holder should be among all threads")
 
 
+class TestUnsupportedPlatformHandling(unittest.TestCase):
+    @unittest.skipIf(
+        sys.platform in ("linux", "darwin", "win32"),
+        "Test only runs on unsupported platforms (not Linux, macOS, or Windows)",
+    )
+    def test_unsupported_platform_error(self):
+        with self.assertRaises(RuntimeError) as cm:
+            RemoteUnwinder(os.getpid())
+
+        self.assertIn(
+            "Reading the PyRuntime section is not supported on this platform",
+            str(cm.exception)
+        )
+
+
 if __name__ == "__main__":
     unittest.main()

Python/remote_debug.h

@@ -888,7 +888,9 @@ _Py_RemoteDebug_GetPyRuntimeAddress(proc_handle_t* handle)
         _PyErr_ChainExceptions1(exc);
     }
 #else
-    Py_UNREACHABLE();
+    _set_debug_exception_cause(PyExc_RuntimeError,
+        "Reading the PyRuntime section is not supported on this platform");
+    return 0;
 #endif
 
     return address;