On Mon, 12 Jan 2009, Bernd Schmidt wrote:

However, if the compiler chooses to put them into the same stack 
location, the RTL-based alias analysis will happily conclude (based on 
the differing types) that the reads from A and the writes to B can't 
possibly conflict, and some passes may end up reordering them. End 
result: overlapping lifetimes and overlapping stack slots.  Oops.

Yes, I came to the same conclusion.

Of course, I knew a-priori that the real bug was using type-based alais 
analysis to make (statically visible) aliasing decisions, but I realize 
that there are people who never understood things like that. Sadly, some 
of them worked on gcc.

			Linus