From: Ben Pfaff Date: Sat, 8 Nov 2008 01:23:09 +0000 (-0800) Subject: Correct comment describing list_remove() behavior. X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=93f894c124abdfa1256fd5b84b94378ed489a1a5;p=pintos-anon Correct comment describing list_remove() behavior. Thanks to Godmar for pointing out the problem. --- diff --git a/src/lib/kernel/list.c b/src/lib/kernel/list.c index e9993cb..316d9ef 100644 --- a/src/lib/kernel/list.c +++ b/src/lib/kernel/list.c @@ -222,21 +222,13 @@ list_push_back (struct list *list, struct list_elem *elem) /* Removes ELEM from its list and returns the element that followed it. Undefined behavior if ELEM is not in a list. - It's not safe to treat ELEM as an element in a list after - removing it. In particular, using list_next() or list_prev() - on ELEM after removal yields undefined behavior. This means - that a naive loop to remove the elements in a list will fail: + A list element must be treated very carefully after removing + it from its list. Calling list_next() or list_prev() on ELEM + will return the item that was previously before or after ELEM, + but, e.g., list_prev(list_next(ELEM)) is no longer ELEM! - ** DON'T DO THIS ** - for (e = list_begin (&list); e != list_end (&list); e = list_next (e)) - { - ...do something with e... - list_remove (e); - } - ** DON'T DO THIS ** - - Here is one correct way to iterate and remove elements from a - list: + The list_remove() return value provides a convenient way to + iterate and remove elements from a list: for (e = list_begin (&list); e != list_end (&list); e = list_remove (e)) {