• Subject: Re: bug in CMPPTRT
  • From: "Leif Svalgaard" <leif@xxxxxxxx>
  • Date: Fri, 29 Sep 2000 17:40:24 -0500

> If I understand correctly, CMPPTRT compares pointer type, not pointer
> values.
> Second operand null means "there is no pointer here".
> So result of first CMPPTRT means, that P is a pointer (it was initialized
> to bad value - probably NULL pointer, but still a pointer), and result of
> second CMPPTRT means that Q is not a pointer (was not initialized - only
> memory allocated).

The actual statement is:
if operand 2 is null (Gene's is) an equal condition occurs if a pointer does
not exist in the storage area identified by operand 1

Nothing about the pointer being valid or the object actually existing.
If you look at the generated code, you'll see that it only checks to
see if the appropriate bits are set in the upper 64 bits of the pointer.

In Gene's case, these bits are set for P (by the INIT) not for Q (no INIT),
hence...


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