Proposal to add gc_list_for_each macro

[nybblista]

Feature or enhancement

Proposal:

In the implementation of the reference cycle garbage collector, gc.c file, I have noticed that we use the following for-loop pattern over and over to traverse a PyGC_Head list:

for (gc = GC_NEXT(list); gc != list; gc = GC_NEXT(gc)) {
  /* ... */
}

However, in pycore_llist.h we avoided that by using llist_for_each macro as:

// Iterate over a list.
#define llist_for_each(node, head) \
    for (node = (head)->next; node != (head); node = node->next)

I propose adding a new macro as gc_list_for_each to the gc_list_xxx family to serve the same purpose:

#define gc_list_for_each(gc, list) \
    for (gc = GC_NEXT((list)); gc != (list); gc = GC_NEXT(gc))

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

[picnixz]

It's mostly cosmetics and I don't think it's worth as it adds a level of indirection in the code, but it's up to the maintainers, namely @markshannon or @colesbury.

Note that = GC_NEXT\(\w+\); \w+ != only has 10 occurrences in the file so it's not that frequent and 3 out of them wouldn't be replacable by this macro.

[colesbury]

Yeah, I'm not sure it's worth it, but I don't feel strongly either way.