Tim Attwood <tim### [at] anti-spamcomcastnet> wrote:
> >  (Btw, AFAIK the C standard specifially says that a null pointer cannot
> > contain a valid value. Thus the compiler can assume that it can't contain
> > a valid value.)

> The problem is that in C a null pointer is represented
> by 0, but 0 is a valid memory address. So when you
> have a valid pointer to address 0, then the optimizer
> thinks you are checking for null, not for address 0.

  Well, dereferencing a null pointer is undefined behavior, so from the point
of view of the standard the compiler can do whatever it wants. Thus gcc is
not doing anything wrong here (because after a null pointer dereference there
is no "wrong" to be done).

  If someone is to be blamed is the designers of the kernel if they decided
that a null pointer points to a valid address, against the C standard, and
then implemented the kernel in C (using a standard-conforming C compiler).

-- 
                                                          - Warp

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