term% cat index.txt 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 pro‐
gram's data space and a pointer to the start of the new area is re‐
turned. Rounding occurs as with brk.
When a program begins execution via exec the break is set at the high‐
est 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)