BREAK(II) 8/5/73 BREAK(II)
NAME
break - set program break
SYNOPSIS
(break = 17.)
sys break; addr
char *brk(addr)
char *sbrk(incr)
DESCRIPTION
Break 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). 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.
From C, brk will set the break to addr. The old break is
returned.
In the alternate entry 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. Ordinarily, therefore, only programs with growing
data areas need to use break.
SEE ALSO
exec (II), alloc (III), end (III)
DIAGNOSTICS
The c-bit is set if the program requests more memory than
the system limit or if more than 8 segmentation registers
would be required to implement the break. From C, -1 is
returned for these errors.