4.3BSD-UWisc/man/cat3/malloc.3f

MALLOC(3F)          UNIX Programmer's Manual           MALLOC(3F)



NAME
     malloc, free, falloc - memory allocator

SYNOPSIS
     subroutine malloc (size, addr)
     integer size, addr

     subroutine free (addr)
     integer addr

     subroutine falloc (nelem, elsize, clean, basevec, addr, offset)
     integer nelem, elsize, clean, addr, offset

DESCRIPTION
     _M_a_l_l_o_c, _f_a_l_l_o_c and _f_r_e_e provide a general-purpose memory
     allocation package.  _M_a_l_l_o_c returns in _a_d_d_r the address of a
     block of at least _s_i_z_e bytes beginning on an even-byte boun-
     dary.

     _F_a_l_l_o_c allocates space for an array of _n_e_l_e_m elements of
     size _e_l_s_i_z_e and returns the address of the block in _a_d_d_r. It
     zeros the block if _c_l_e_a_n is 1.  It returns in _o_f_f_s_e_t an
     index such that the storage may be addressed as
     _b_a_s_e_v_e_c(_o_f_f_s_e_t+_1) ... _b_a_s_e_v_e_c(_o_f_f_s_e_t+_n_e_l_e_m). _F_a_l_l_o_c gets
     extra bytes so that after address arithmetic, all the
     objects so addressed are within the block.

     The argument to _f_r_e_e is the address of a block previously
     allocated by _m_a_l_l_o_c or _f_a_l_l_o_c; this space is made available
     for further allocation, but its contents are left undis-
     turbed.  To free blocks allocated by _f_a_l_l_o_c, use _a_d_d_r in
     calls to _f_r_e_e, do not use _b_a_s_e_v_e_c(_o_f_f_s_e_t+_1).

     Needless to say, grave disorder will result if the space
     assigned by _m_a_l_l_o_cor_f_a_l_l_o_c is overrun or if some random
     number is handed to _f_r_e_e.

DIAGNOSTICS
     _M_a_l_l_o_c and _f_a_l_l_o_c set _a_d_d_r to 0 if there is no available
     memory or if the arena has been detectably corrupted by
     storing outside the bounds of a block.

     The following example shows how to obtain memory and use it
     within a subprogram:

           integer addr, work(1), offset
              ...
           call falloc ( n, 4, 0, work, addr, offset )
           do 10 i = 1, n
           work(offset+i) = ...
     10    continue




Printed 12/27/86          May 15, 1985                          1






MALLOC(3F)          UNIX Programmer's Manual           MALLOC(3F)



     The next example reads in dimension information, allocates
     space for two arrays and two vectors, and calls subroutine
     _d_o_i_t to do the computations:

           integer addr, dummy(1), offs
           read *, k, l, m
           indm1   = 1
           indm2   = indm1 + k*l
           indm3   = indm2 + l*m
           indsym  = indm3 + k*m
           lsym = n*(n+1)/2
           indv  = indsym + lsym
           indtot = indv + m
           call falloc ( indtot, 4, 0, dummy, addr, offs )
           call doit( dummy(indm1+offs), dummy(indm2+offs),
          .           dummy(indm3+offs), dummy(indsym+offs),
          .           dummy(indv +offs), m, n, lsym )
           end
           subroutine doit( arr1, arr2, arr3, vsym, vec, m, n, lsym )
           real arr1(k,l), arr2(l,m), arr3(k,m), vsym(lsym), v2(m)
              ...

FILES
     /usr/lib/libU77.a

SEE ALSO
     malloc(3)




























Printed 12/27/86          May 15, 1985                          2