brk(2) [plan9 man page]

BRK(2)								System Calls Manual							    BRK(2)

NAME

       brk, sbrk - change memory allocation

SYNOPSIS

       #include <u.h>
       #include <libc.h>

       int   brk(void *addr)

       void* sbrk(ulong incr)

DESCRIPTION

       Brk sets the system's idea of the lowest bss location not used by the program (called the break) to addr rounded up to the next multiple of
       8 bytes.  Locations not less than addr and below the stack pointer may cause a memory violation if accessed.

       In the alternate function sbrk, incr more bytes are added to the program's data space and a pointer  to	the  start  of	the  new  area	is
       returned.  Rounding occurs as with brk.

       When  a program begins execution via exec the break is set at the highest location defined by the program and data storage areas.  Ordinar-
       ily, therefore, only programs with growing data areas need to use brk.  A call to sbrk with a zero argument returns the lowest  address	in
       the dynamic segment.

SOURCE

       /sys/src/libc/9sys/sbrk.c

SEE ALSO

       intro(2), malloc(2), segattach(2), segbrk(2)

DIAGNOSTICS

       These functions set errstr.

       The error return from sbrk is (void*)-1.

																	    BRK(2)

BRK(2)								System Calls Manual							    BRK(2)

NAME

       brk, sbrk, break - change core allocation

SYNOPSIS

       char *brk(addr)

       char *sbrk(incr)

DESCRIPTION

       Brk sets the system's idea of the lowest location not used by the program (called the break) to addr (rounded up to the next multiple of 64
       bytes on the PDP11, 256 bytes on the Interdata 8/32, 512 bytes on the VAX-11/780).  Locations not  less	than  addr  and  below	the  stack
       pointer are not in the address space and will thus cause a memory violation if accessed.

       In  the	alternate  function  sbrk,  incr  more	bytes  are added to the program's data space and a pointer to the start of the new area is
       returned.

       When a program begins execution via exec the break is set at the highest location defined by the program and data storage areas.   Ordinar-
       ily, therefore, only programs with growing data areas need to use break.

SEE ALSO

       exec(2), malloc(3), end(3)

DIAGNOSTICS

       Zero is returned if the break could be set; -1 if the program requests more memory than the system limit or if too many segmentation regis-
       ters would be required to implement the break.

BUGS

       Setting the break in the range 0177701 to 0177777 (on the PDP11) is the same as setting it to zero.

ASSEMBLER

       (break = 17.)
       sys break; addr

       Break performs the function of brk.  The name of the routine differs from that in C for historical reasons.

																	    BRK(2)