V8/usr/man/man2/brk.2

.TH BRK 2 
.SH NAME
brk, sbrk, break \- change core allocation
.SH SYNOPSIS
.B char *brk(addr)
.PP
.B char *sbrk(incr)
.SH DESCRIPTION
.I Brk
sets the system's idea of the lowest location not used by the program
(called the break)
to
.I addr
(rounded up to the next multiple of 64 bytes
on a PDP11
and 1024 bytes on a VAX).
Locations not less than
.I addr
and below the stack pointer
are not in the address space and will thus
cause a memory violation if accessed.
.PP
In the alternate function
.I 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
.I brk,
but a nominal break is remembered, so rounding does not accumulate.)
.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 break .
.SH "SEE ALSO"
exec(2),
malloc(3),
end(3)
.SH DIAGNOSTICS
Zero is returned if the 
.I brk
could be set;
\-1 if the program requests more
memory than the system limit
or if too many segmentation
registers would be required to implement the break.
.I Sbrk
returns \-1 if the break could not be set.