C undefined behavior fix

From: Paul Mackerras <[email protected]>
Date: Sun, 6 Jan 2002 16:32:05 +1100 (EST)

* I need a way to tell the compiler not to make any assumptions about what objects that such a pointer might or might not point to, so that the effect of dereferencing the pointer is simply to access the memory at the address I gave, and is not considered "undefined" regardless of how I might have constructed the address.

GCC already does the first and third, but there doesn't seem to be a clean and reliable way to do the second.