Xinu7/man/man2/getmem.doc

GETMEM(2)           Xinu Programmer's Manual            GETMEM(2)



NAME
     getmem, getstk - get a block of main memory

SYNOPSIS
     char *getmem(nbytes)
     int nbytes;

     char *getstk(nbytes)
     int nbytes;

DESCRIPTION
     In either form, _g_e_t_m_e_m rounds the number of bytes, _n_b_y_t_e_s,
     to an even-word multiple, and allocates a block of _n_b_y_t_e_s
     bytes of memory for the caller.  _G_e_t_m_e_m returns the lowest
     word address in the allocated block; _g_e_t_s_t_k returns the
     highest word address in the allocated block.  If less than
     _n_b_y_t_e_s bytes remain, the call returns SYSERR.

     _G_e_t_m_e_m allocates memory starting with the end of the loaded
     program.  _G_e_t_s_t_k allocates memory from the stack area down-
     ward.  The routines cooperate so they never allocate over-
     lapping regions.

SEE ALSO
     freemem(2) getbuf(2), freebuf(2)

BUGS
     There is no way to protect memory, so the active stack may
     write into regions returned by either call; allocations
     returned by _g_e_t_s_t_k are more prone to disaster because they
     lie closest to the dynamic stack areas of other processes.
























Version 6b               Printed 1/12/87                        1