SimStruct representing an S-Function block or a Simulink® model.
The parent SimStruct of S,
or NULL if S is the root SimStruct.
Use to obtain the parent of a SimStruct.
There is one SimStruct for each S-function
in your model and one for the model itself. The structures are arranged
as a tree with the model SimStruct as the root.
This macro is for internal use. User-written S-functions should not
use the ssGetParentSS macro.