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Re: US-CERT Vulnerability Note VU#162289
Gerald.Williams@infineon.com wrote:
It's already been acknowledged that the source code is wrong
to assume that the compiler knows about wrapping of pointers.
The real issue at this stage is how to warn users who may be
using GCC and implicitly relying on its old behavior, without
unintentionally pushing people in the wrong direction. Since
this optimization is performed by many other compilers, the
ship has already sailed on this one, so to speak.
that's a strong argument I agree
[In fact,
after GCC does something to warn users about this, it'll be
much "safer" than those other compilers.]
For sure you want a warning, the compiler should never be
removing explicit tests in the users code without generating
a warning I would think.
I agree that on the face of it, it seems like you wouldn't
want to optimize away tests like this when you can know that
pointer arithmetic really does look the same as unsigned
arithmetic (for a particular architecture, etc.). However,
sometimes an optimization may enable thirty more, so I for
one am not going to argue against it. Especially not when
many other compilers do it also.
Not sure I agree with that, but I can certainly live with
a warning.
-Jerry
P.S. I'm having some déjà vu, recalling discussions back in
the GCC 2.7 days about whether it was really OK to change
the behavior for signed arithmetic to support devices with
saturation. We've come a long way since then.
:-)