--- /dev/null
+.\" $NetBSD: brk.2,v 1.7 1995/02/27 12:31:57 cgd Exp $
+.\"
+.\" Copyright (c) 1980, 1991, 1993
+.\" The Regents of the University of California. 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.
+.\" 3. All advertising materials mentioning features or use of this software
+.\" must display the following acknowledgement:
+.\" This product includes software developed by the University of
+.\" California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\" may be used to endorse or promote products derived from this software
+.\" without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
+.\"
+.\" @(#)brk.2 8.2 (Berkeley) 12/11/93
+.\"
+.Dd December 11, 1993
+.Dt BRK 2
+.Os BSD 4
+.Sh NAME
+.Nm brk ,
+.Nm sbrk
+.Nd change data segment size
+.Sh SYNOPSIS
+.Fd #include <unistd.h>
+.Ft void *
+.Fn brk "const void *addr"
+.Ft void *
+.Fn sbrk "int incr"
+.Sh DESCRIPTION
+.Bf -symbolic
+The brk and sbrk functions are historical curiosities
+left over from earlier days before the advent of virtual memory management.
+.Ef
+The
+.Fn brk
+function
+sets the break or lowest address
+of a process's data segment (uninitialized data) to
+.Fa addr
+(immediately above bss).
+Data addressing is restricted between
+.Fa addr
+and the lowest stack pointer to the stack segment.
+Memory is allocated by
+.Fa brk
+in page size pieces;
+if
+.Fa addr
+is not evenly divisible by the system page size, it is
+increased to the next page boundary.
+.Pp
+.\" The
+.\" .Nm sbrk
+.\" function
+.\" allocates chunks of
+.\" .Fa incr
+.\" bytes
+.\" to the process's data space
+.\" and returns an address pointer.
+.\" The
+.\" .Xr malloc 3
+.\" function utilizes
+.\" .Nm sbrk .
+.\" .Pp
+The current value of the program break is reliably returned by
+.Dq Li sbrk(0)
+(see also
+.Xr end 3 ) .
+The
+.Xr getrlimit 2
+system call may be used to determine
+the maximum permissible size of the
+.Em data
+segment;
+it will not be possible to set the break
+beyond the
+.Em rlim_max
+value returned from a call to
+.Xr getrlimit ,
+e.g.
+.Dq qetext + rlp\(->rlim_max.
+(see
+.Xr end 3
+for the definition of
+.Em etext ) .
+.Sh RETURN VALUES
+.Nm Brk
+returns a pointer to the new end of memory if successful;
+otherwise -1 with
+.Va errno
+set to indicate why the allocation failed.
+The
+.Nm sbrk
+function returns a pointer to the base of the new storage if successful;
+otherwise -1 with
+.Va errno
+set to indicate why the allocation failed.
+.Sh ERRORS
+.Xr Sbrk
+will fail and no additional memory will be allocated if
+one of the following are true:
+.Bl -tag -width Er
+.It Bq Er ENOMEM
+The limit, as set by
+.Xr setrlimit 2 ,
+was exceeded.
+.It Bq Er ENOMEM
+The maximum possible size of a data segment (compiled into the
+system) was exceeded.
+.It Bq Er ENOMEM
+Insufficient space existed in the swap area
+to support the expansion.
+.El
+.Sh SEE ALSO
+.Xr execve 2 ,
+.Xr getrlimit 2 ,
+.Xr malloc 3 ,
+.Xr mmap 2 ,
+.Xr end 3
+.Sh BUGS
+Setting the break may fail due to a temporary lack of
+swap space. It is not possible to distinguish this
+from a failure caused by exceeding the maximum size of
+the data segment without consulting
+.Xr getrlimit .
+.Sh HISTORY
+A
+.Fn brk
+function call appeared in
+.At v7 .
projects / apple / libc.git / blobdiff