NAME

break, brk, sbrk − change core allocation

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. 

BUGS

Setting the break in the range 0177700 to 0177777 is the same as setting it to zero.