builtin bounds checking how-to

["Brian McQueen" <mcqueenorama at gmail dot com>]

I see a slight reference to some builtin object size checking
functionality provided by gcc.  But from the documentation I am not
able to guess how to use many of the builtins provided, such as:

__builtin___sprintf_chk

and

__builtin___printf_chk

and the others mentioned in the gcc info pages under Object Size
Checking.  I'd like to use these things.

Would someone please point me in the right direction so I can get
these things going?  In particular what is the 'implementation
specific flag' that is to be passed as an argument?

Thanks for any help on this.

Brin McQueen