On Fri, 20 Jun 2025 16:47:29 +0000, Farley, Peter <[email protected]>
wrote:
>I would THINK that if an object on a heap is deleted, then a second delete
>request for that same object SHOULD return an error (invalid object address at
>least), which of course the programmer should be checking . . . but regardless
>of checked or not checked, the effect of a second delete SHOULD not cause any
>storage error in any rational heap system of which I can conceive.
>
>Was this a custom heap library or some existing standard heap library?
There is no return value from a delete so there is no way to check for an
error. I would appreciate an assert or similar.
This is the utterly vanilla XLC C++/LE heap library.
If I am reading the docs correctly a bad delete used to throw but now the
behavior is undefined.
It is my usual practice to follow a delete with setting the pointer to nullptr
(zero). This has two benefits: (1) if one then tries to de-reference ("use")
the pointer one gets an immediate fault rather than whatever the old address
might happen to point to; and (2) a subsequent duplicate delete is a no-op.
(Standard C++ behavior -- delete of a nullptr is a no-op.) I obviously failed
to follow my own practice in this case. (And yes, it's not perfect. A program
might have more than one pointer to an on-heap object.)
Charles
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