Continuing the theme of cleaning up old and weird stuff in the code, I
propose to remove the Item type. It's defined as
typedef Pointer Item;
(note that Pointer is char *), and its almost only use is as part of
PageAddItem*():
extern OffsetNumber PageAddItemExtended(Page page, Item item, Size size,
OffsetNumber offsetNumber, int flags);
The actual thing passed to PageAddItem*() is of some AM-specific type,
and so that forces casts in all calls, like
offnum = PageAddItem(page, (Item) tuple, tuplen, offnum, true, false);
So this type doesn't promote any type safety, but in fact sort of forces
the opposite.
And then we have the usual problem that this is a type that hides
pointerness, and so we can't add any qualifiers, which leads to some
unconstify nonsense.
(Also, Item is unrelated to ItemPointer, which seems confusing.)
Initially I considered creating some underlying type to point to like
ItemData, but that didn't seem useful. Ultimately, PageAddItem*() is
just a fancy memcpy(), and using void * is an idiomatic way to refer to
a generic chunk of memory. So I'm proposing to remove the Item type,
replace it with void * in function prototypes, and remove all the casts.
Extension authors can make their code backward compatible by replacing
PageAddItem(page, (Item) tuple, ...)
with
PageAddItem(page, (void *) tuple, ...)