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brk, sbrk, break - change core allocation
Brk 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 on the PDP11, 256 bytes on the
Interdata 8/32, 512 bytes on the VAX-11/780). Locations not less than addr and below the
stack pointer are not in the address space and will thus cause a memory violation if
In the alternate function 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.
exec(2), malloc(3), end(3)
Zero is returned if the break 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
Setting the break in the range 0177701 to 0177777 (on the PDP11) is the same as setting it
(break = 17.)
sys break; addr
Break performs the function of brk. The name of the routine differs from that in C for
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