TH BRK 2
SH NAME
brk, sbrk \- change memory allocation
SH SYNOPSIS
B #include <u.h>
br
B #include <libc.h>
PP
ta \w'\fLvoid* 'u
B
int brk(void *addr)
PP
B
void* sbrk(ulong incr)
SH DESCRIPTION
I Brk
sets the system's idea of the lowest bss location not used by the program
(called the break)
to
I addr
rounded up to the next multiple of 8 bytes.
Locations not less than
I addr
and below the stack pointer
may cause a memory violation if accessed.
PP
In the alternate function
IR sbrk ,
I 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
IR brk .
PP
When a program begins execution via
I exec
the break is set at the
highest location defined by the program
and data storage areas.
Ordinarily, therefore, only programs with growing
data areas need to use
IR brk .
A call to
I sbrk
with a zero argument returns the lowest address
in the dynamic segment.
SH SOURCE
B /sys/src/libc/9sys/sbrk.c
SH SEE ALSO
IR intro (2),
IR malloc (2),
IR segattach (2),
IR segbrk (2)
SH DIAGNOSTICS
These functions set
IR errstr .
PP
The error return from
I sbrk
is
BR (void*)-1 .
