Subtyping support in GCC?

[Jason Chagas]

The the ARM compiler (armcc) provides a subtyping ($Sub/$Super)
mechanism useful as a patching technique (see links below for
details). Can someone tell me if GCC has similar support? If so, where
can I learn more about it?

FYI, before posting this question here, I researched the web
extensivelly on this topic. There seems to be some GNU support for
subtyping in C++.  But I had no luck finding any information
specifically for 'C'.

Thanks,

Jason

How to use $Super$$ and $Sub$$ for patching data?:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka15416.html

Using $Super$$ and $Sub$$ to patch symbol definitions:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0474c/Chdefdce.html