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gc list function cleanup.

Browse source 
Introduced gc_list_move(), which captures the common gc_list_remove() +
gc_list_append() sequence.  In fact, no uses of gc_list_append() remained
(they were all in a gc_list_move() sequence), so commented that one out.

gc_list_merge():  assert that `from` != `to`; that was an implicit
precondition, now verified in a debug build.

Others:  added comments about their purpose.
This commit is contained in:
Tim Peters 2004-11-01 01:39:08 +00:00
parent cc2a866cb7
commit e2d591847c
1 changed files with 31 additions and 15 deletions
Download patch file Download diff file Expand all files Collapse all files

46
Modules/gcmodule.c
View file

@ -139,6 +139,9 @@ gc_list_is_empty(PyGC_Head *list)
return (list->gc.gc_next == list);
}
#if 0
/* This became unused after gc_list_move() was introduced. */
/* Append `node` to `list`. */
static void
gc_list_append(PyGC_Head *node, PyGC_Head *list)
{
@ -147,7 +150,9 @@ gc_list_append(PyGC_Head *node, PyGC_Head *list)
node->gc.gc_prev->gc.gc_next = node;
list->gc.gc_prev = node;
}
#endif
/* Remove `node` from the gc list it's currently in. */
static void
gc_list_remove(PyGC_Head *node)
{
@ -156,11 +161,29 @@ gc_list_remove(PyGC_Head *node)
node->gc.gc_next = NULL; /* object is not currently tracked */
}
/* append a list onto another list, from becomes an empty list */
/* Move `node` from the gc list it's currently in (which is not explicitly
* named here) to the end of `list`. This is semantically the same as
* gc_list_remove(node) followed by gc_list_append(node, list).
*/
static void
gc_list_move(PyGC_Head *node, PyGC_Head *list)
{
PyGC_Head *current_prev = node->gc.gc_prev;
PyGC_Head *current_next = node->gc.gc_next;
PyGC_Head *new_prev = list->gc.gc_prev;
current_prev->gc.gc_next = current_next;
current_next->gc.gc_prev = current_prev;
node->gc.gc_next = list;
node->gc.gc_prev = new_prev;
new_prev->gc.gc_next = list->gc.gc_prev = node;
}
/* append list `from` onto list `to`; `from` becomes an empty list */
static void
gc_list_merge(PyGC_Head *from, PyGC_Head *to)
{
PyGC_Head *tail;
assert(from != to);
if (!gc_list_is_empty(from)) {
tail = to->gc.gc_prev;
tail->gc.gc_next = from->gc.gc_next;
@ -295,8 +318,7 @@ visit_reachable(PyObject *op, PyGC_Head *reachable)
* and move_unreachable will eventually get to it
* again.
*/
gc_list_remove(gc);
gc_list_append(gc, reachable);
gc_list_move(gc, reachable);
gc->gc.gc_refs = 1;
}
/* Else there's nothing to do.
@ -368,8 +390,7 @@ move_unreachable(PyGC_Head *young, PyGC_Head *unreachable)
* young if that's so, and we'll see it again.
*/
next = gc->gc.gc_next;
gc_list_remove(gc);
gc_list_append(gc, unreachable);
gc_list_move(gc, unreachable);
gc->gc.gc_refs = GC_TENTATIVELY_UNREACHABLE;
}
gc = next;
@ -416,8 +437,7 @@ move_finalizers(PyGC_Head *unreachable, PyGC_Head *finalizers)
next = gc->gc.gc_next;
if (has_finalizer(op)) {
gc_list_remove(gc);
gc_list_append(gc, finalizers);
gc_list_move(gc, finalizers);
gc->gc.gc_refs = GC_REACHABLE;
}
}
@ -430,8 +450,7 @@ visit_move(PyObject *op, PyGC_Head *tolist)
if (PyObject_IS_GC(op)) {
if (IS_TENTATIVELY_UNREACHABLE(op)) {
PyGC_Head *gc = AS_GC(op);
gc_list_remove(gc);
gc_list_append(gc, tolist);
gc_list_move(gc, tolist);
gc->gc.gc_refs = GC_REACHABLE;
}
}
@ -559,8 +578,7 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
assert(wrasgc != next); /* wrasgc is reachable, but
next isn't, so they can't
be the same */
gc_list_remove(wrasgc);
gc_list_append(wrasgc, &wrcb_to_call);
gc_list_move(wrasgc, &wrcb_to_call);
}
}
@ -600,8 +618,7 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
Py_DECREF(op);
if (wrcb_to_call.gc.gc_next == gc) {
/* object is still alive -- move it */
gc_list_remove(gc);
gc_list_append(gc, old);
gc_list_move(gc, old);
}
else
++num_freed;
@ -694,8 +711,7 @@ delete_garbage(PyGC_Head *collectable, PyGC_Head *old)
}
if (collectable->gc.gc_next == gc) {
/* object is still alive, move it, it may die later */
gc_list_remove(gc);
gc_list_append(gc, old);
gc_list_move(gc, old);
gc->gc.gc_refs = GC_REACHABLE;
}
}