[plt-scheme] Testing a pointer for null (FFI)

Thanks.  I'll go with the test for zero, which feels a tiny
bit sleazy and I don't recall the C standard specifying
NULL == 0 but works on every implementation I've ever used.

N.

--- Eli Barzilay <eli at barzilay.org> wrote:

...
> ... it seems that you have a pointer to a pointer, so you
> have to do
> that `ptr-ref'.  You can either do the above, or use
> (ptr-ref the-pointer _pointer) and check if it's #f or
> not.  Both are
> fine since NULL is 0, and using _pointer will cost one
> malloc if the
> pointer is not NULL (but who's counting?)...

...

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