1.\" $NetBSD: __builtin_object_size.3,v 1.1 2007/05/30 01:17:31 tls Exp $ 2.\" 3.\" Copyright (c) 2007 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to The NetBSD Foundation 7.\" by Christos Zoulas. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the NetBSD 20.\" Foundation, Inc. and its contributors. 21.\" 4. Neither the name of The NetBSD Foundation nor the names of its 22.\" contributors may be used to endorse or promote products derived 23.\" from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 26.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 29.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35.\" POSSIBILITY OF SUCH DAMAGE. 36.\" 37.\" 38.Dd May 23, 2007 39.Dt __BUILTIN_OBJEXT_SIZE 3 40.Os 41.Sh NAME 42.Nm __builtin_object_size 43.Nd return the size of the given object 44.Sh LIBRARY 45.Ft size_t 46.Fn __builtin_object_size "void *ptr" "int type" 47.Sh DESCRIPTION 48The 49.Fn __builtin_object_size 50function is a 51.Xr gcc 1 52built-in function that returns the size of the 53.Fa ptr 54object if known at compile time and the object does not have any side 55effects. 56.Sh RETURN VALUES 57If the size of the object is not known or it has side effects the 58.Fn __builtin_object_size 59function returns: 60.Bl -tag -width (size_t)-1 61.It Dv (size_t)-1 62for 63.Fa type 64.Dv 0 65and 66.Dv 1 . 67.It Dv (size_t)0 68for 69.Fa type 70.Dv 2 71and 72.Dv 3 . 73.El 74.Pp 75If the size of the object is known, then the 76.Fn __builtin_object_size 77function returns the maximum size of all the objects that the compiler 78knows that they can be pointed to by 79.Fa ptr 80when 81.Fa type 82.Dv & 2 == 0 , 83and the minimum size when 84.Fa type 85.Dv & 2 != 0 . 86.Sh SEE ALSO 87.Xr gcc 1 , 88.Xr ssp 3 . 89.Sh HISTORY 90The 91.Fn __builtin_object_size 92appeared in gcc 4.1. 93