[PATCH] C undefined behavior fix

[dewar@gnat.com]

<<We have seen much trouble in this area before, but I doubt we can
avoid all of them by proper documentation.  Quite a few people seem to
write some C code, check that it works, look at the generated machine
code, and if it seems to be correct, the C code is considered to be
correct.
>>

We can't avoid people writing wrong code, but we can avoid debate as to
whether the code is right or wrong :-)