[RFC] Program Bounds Checking

[David Edelsohn <dje at watson dot ibm dot com>]

	Tzi-cker Chiueh has developed a low-overhead bounds checking
feature and approached the FSF about having it incorporated in GCC.  This
discussion originally was forwarded to the GCC Steering Committee, so I am
redirecting the conversation to the main GCC mailinglist.  Hopefully some
members of the GCC community who are knowledgeable about this type of
technology will follow up with Tzi-cker.

Thanks, David

------- Forwarded Message

Mudflap performs not-so-complete bound checking on C programs. Already its
performance overhead is 300%-500% of the original execution time.  Our
initial bound checking compiler, CASH
(http://www.ecsl.cs.sunysb.edu/cash/index.html), can perform complete
bound checking for C programs with a performance overhead of less than
10%.

The reason it can achieve this feat is because it exploits segmentation
hardware on X86/IA32 architecture. Because segmentation hardware is not
supported in IA64 and other embedded processors, our current proposal is
to exploit "debug resgister" hardware, which is more universal, to achieve
the same array bound checking performance level as CASH.

CASH's low run-time overhead makes it practical for the first time to turn
on bound checking for production-mode server programs such as Apache or
BIND.

------- End of Forwarded Message