diff options
Diffstat (limited to 'share/man/man3')
| -rw-r--r-- | share/man/man3/queue.3 | 40 |
1 files changed, 29 insertions, 11 deletions
diff --git a/share/man/man3/queue.3 b/share/man/man3/queue.3 index f4329c0f1a6..dcc5fc4ffac 100644 --- a/share/man/man3/queue.3 +++ b/share/man/man3/queue.3 @@ -1,4 +1,4 @@ -.\" $OpenBSD: queue.3,v 1.37 2005/01/04 20:45:01 jaredy Exp $ +.\" $OpenBSD: queue.3,v 1.38 2005/10/27 19:27:10 otto Exp $ .\" $NetBSD: queue.3,v 1.4 1995/07/03 00:25:36 mycroft Exp $ .\" .\" Copyright (c) 1993 The Regents of the University of California. @@ -615,11 +615,11 @@ LIST_INSERT_AFTER(n1, n2, entries); n2 = malloc(sizeof(struct entry)); /* Insert before. */ LIST_INSERT_BEFORE(n1, n2, entries); /* Forward traversal. */ -for (np = head.lh_first; np != NULL; np = np->entries.le_next) +LIST_FOREACH(np, &head, entries) np-> ... -while (head.lh_first != NULL) /* Delete. */ - LIST_REMOVE(head.lh_first, entries); +while (!LIST_EMPTY(&head)) /* Delete. */ + LIST_REMOVE(LIST_FIRST(&head), entries); .Ed .Sh SIMPLE QUEUES A simple queue is headed by a structure defined by the @@ -727,10 +727,10 @@ SIMPLEQ_INSERT_AFTER(&head, n1, n2, entries); n2 = malloc(sizeof(struct entry)); /* Insert at the tail. */ SIMPLEQ_INSERT_TAIL(&head, n2, entries); /* Forward traversal. */ -for (np = SIMPLEQ_FIRST(&head); np != NULL; np = SIMPLEQ_NEXT(np, entries)) +SIMPLEQ_FOREACH(np, &head, entries) np-> ... /* Delete. */ -while ((n1 = SIMPLEQ_FIRST(&head)) != NULL) +while (!SIMPLEQ_EMPTY(&head)) SIMPLEQ_REMOVE_HEAD(&head, entries); .Ed .Sh TAIL QUEUES @@ -1000,18 +1000,22 @@ CIRCLEQ_INSERT_AFTER(&head, n1, n2, entries); n2 = malloc(sizeof(struct entry)); /* Insert before. */ CIRCLEQ_INSERT_BEFORE(&head, n1, n2, entries); /* Forward traversal. */ -for (np = CIRCLEQ_FIRST(&head); np != CIRCLEQ_END(&head); - np = CIRCLEQ_NEXT(np, entries)) +CIRCLEQ_FOREACH(np, &head, entries) np-> ... /* Reverse traversal. */ -for (np = CIRCLEQ_LAST(&head); np != CIRCLEQ_END(&head); - np = CIRCLEQ_PREV(np, entries)) +CIRCLEQ_FOREACH_REVERSE(np, &head, entries) np-> ... /* Delete. */ -while (CIRCLEQ_FIRST(&head) != CIRCLEQ_END(&head)) +while (!CIRCLEQ_EMPTY(&head)) CIRCLEQ_REMOVE(&head, CIRCLEQ_FIRST(&head), entries); .Ed .Sh NOTES +It is an error to assume the next and previous fields are preserved +after an element has been removed from a list or queue. +Using any macro (except the various forms of insertion) on an element +removed from a list or queue is incorrect. +An example of erroneous usage is removing the same element twice. +.Pp The .Fn SLIST_END , .Fn LIST_END , @@ -1044,6 +1048,20 @@ for (var = LIST_FIRST(head); var != LIST_END(head); var = nxt) { } LIST_INIT(head); /* to put the list back in order */ .Ed +.Pp +A similar situation occurs when the current element is deleted +from the list. +Correct code saves a pointer to the next element in the list before +removing the element: +.Bd -literal -offset indent +for (var = LIST_FIRST(head); var != LIST_END(head); var = nxt) { + nxt = LIST_NEXT(var, entry); + if (some_condition) { + LIST_REMOVE(var, entry); + some_function(var); + } +} +.Ed .Sh HISTORY The .Nm queue |