|BRK(2)||System Calls Manual||BRK(2)|
sbrk() functions are historical curiosities left over from earlier days before the advent of virtual memory management.
brk() function sets the break or lowest address of a process's data segment (uninitialized data) to addr (immediately above bss). Data addressing is restricted between addr and the lowest stack pointer to the stack segment. Memory is allocated by
brk() in page size pieces; if addr is not evenly divisible by the system page size, it is increased to the next page boundary.
The current value of the program break is reliably returned by
sbrk(0)” (see also
getrlimit(2) system call may be used
to determine the maximum permissible size of the data
segment; it will not be possible to set the break beyond the
rlim_max value returned from a call to
etext + rlp->rlim_max’ (see
end(3) for the definition of
brk() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
sbrk() function returns a pointer to
the base of the new storage if successful; otherwise -1 with
errno set to indicate why the allocation failed.
sbrk() will fail and no additional memory will be allocated if one of the following are true:
brk() function call appeared in Version 7 AT&T UNIX.
|October 11, 2015||OpenBSD-current|