Re: RFA: New pass to delete unexecutable paths in the CFG

[Jeff Law <law@redhat.com>]

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On 11/07/11 06:53, Tom Tromey wrote:
>>>>>> "Jeff" == Jeff Law <law@redhat.com> writes:
> 
> Jeff> First, it's perfectly fine to have a NULL pointer dereference
> in a Jeff> program as long as that code is never executed.  Once
> the code is Jeff> executed, we've entered the realm of undefined
> behavior.
> 
> Jeff> Thus in a conforming program we can safely assume that a
> provable NULL Jeff> pointer dereference can never be executed at
> runtime.  This implies Jeff> there is a path through the CFG that
> is unexecutable.
> 
> IIUC, then this isn't true for Java.  In Java the attempt to
> dereference NULL throws a NullPointerException, which can be
> caught, etc.  It isn't undefined.
So, presumably there's no way to know we're throwing to
NullPointerException from the exception information attached to the
statement or BB?  If not I could disable if the statement with the
memory op throws anywhere.  It's not ideal, but conservatively correct.

jeff

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