container_of.3 revision 1.2.4.2 $NetBSD: container_of.3,v 1.2.4.2 2025/08/02 05:55:10 perseant Exp $
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.Dd October 8, 2011 .Dt CONTAINER_OF 3 .Os .Sh NAME .Nm container_of .Nd cast a pointer to member of a structure to a pointer of its container structure. .Sh SYNOPSIS n sys/container_of.h .Ft "type *" .Fn container_of "pointer" "type" "member" .Sh DESCRIPTION Given a .Fa pointer that points to a .Fa member of the container structure .Fa type the .Fn container_of macro returns a pointer that points to the enclosing container structure.
Copyright (c) 2024 The NetBSD Foundation, Inc.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
.Dd October 8, 2011 .Dt CONTAINER_OF 3 .Os .Sh NAME .Nm container_of .Nd cast a pointer to member of a structure to a pointer of its container structure. .Sh SYNOPSIS n sys/container_of.h .Ft "type *" .Fn container_of "pointer" "type" "member" .Sh DESCRIPTION Given a .Fa pointer that points to a .Fa member of the container structure .Fa type the .Fn container_of macro returns a pointer that points to the enclosing container structure.
p A compiler error will result if .Ar member is not aligned to a byte boundary
q i.e. it is a bit-field . .Sh EXAMPLES d -literal #include <assert.h> #include <sys/container_of.h> struct container { double other_member; int member; }; struct container one; void test(void) { int *ptr = &one.member; struct container *onep = container_of(ptr, struct container, member); assert(onep == &one); } .Ed .Sh SEE ALSO .Xr __alignof__ 3 , .Xr offsetof 3 , .Xr stddef 3 , .Xr typeof 3 .Sh HISTORY The .Fn container_of macro appeared first in the Linux kernel.
Indexes created Sat Nov 08 12:09:53 GMT 2025