Re: Potential for bugs while using COPY_POINTER_FIELD to copy NULL pointer

Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> writes:
> After such a copy tests like if (pointer) will start failing. There are few
> callers of COPY_POINTER_FIELD which do not call the macro if the size can
> be 0. But there are some who do not do so. This looks fishy, in case we
> have if (pointer) kinds of cases.

I don't think we do. That macro is only used to copy fixed-length
support arrays like sort column numbers. There would be no reason to
test such a field for null-ness; its size is always determined by other
properties of the node.

It does look like all the actual uses of the macro are protected by
if-tests if the number of columns could be zero (except for MergeJoin
which didn't use to support zero columns but now does; should go fix
that). But AFAICS that is purely to save a couple of cycles in the copy
operation, not because it would matter later.

regards, tom lane