I happened to be looking at nodes.h and started wondering just how
sane this coding really is:
extern PGDLLIMPORT Node *newNodeMacroHolder;
#define newNode(size, tag) \
( \ AssertMacro((size) >= sizeof(Node)), /* need the tag, at least */ \ newNodeMacroHolder = (Node *)
palloc0fast(size),\ newNodeMacroHolder->type = (tag), \ newNodeMacroHolder \
)
Given that we're calling palloc, it's not clear that saving one level of
function call is really buying much; and what it's costing us is a store
to a global variable that the compiler has no way to optimize away.
On a lot of platforms, accessing global variables isn't especially
cheap. Also, considering that palloc0fast is a nontrivial macro, and
that there are a LOT of uses of newNode(), we're paying rather a lot of
code space for a pretty dubious savings.
So I'm tempted to get rid of this and just make newNode() an out-of-line
function.
Thoughts?
regards, tom lane
