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

NAME
     malloc, free, realloc, calloc - main memory allocator

SYNOPSIS
     char *malloc (size)
     unsigned size;

     free (ptr)
     char *ptr;

     char *realloc (ptr, size)
     char *ptr;
     unsigned size;

     char *calloc (nelem, elsize)
     unsigned nelem, elsize;

HP-UX COMPATIBILITY
     Level:    HP-UX/RUN ONLY

     Origin:   System III

DESCRIPTION
     _M_a_l_l_o_c and _f_r_e_e  provide  a  simple  general-purpose  memory
     allocation  package.  _M_a_l_l_o_c returns a pointer to a block of
     at least _s_i_z_e bytes beginning  on  a  word  boundary.   Note
     that,  for  requests for zero bytes (_s_i_z_e = 0), _m_a_l_l_o_c still
     returns a valid pointer.  The allocated block of  memory  is
     not initialized in any way.

     The argument to _f_r_e_e is a  pointer  to  a  block  previously
     allocated  by  _m_a_l_l_o_c;  this  space  is  made  available for
     further allocation, but its contents are left undisturbed.

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

     _M_a_l_l_o_c allocates the first big enough  contiguous  reach  of
     free  space  found  in a circular search from the last block
     allocated or freed, coalescing adjacent free  blocks  as  it
     searches.   It  calls  _s_b_r_k  (see _b_r_k(2)) to get more memory
     from the system when there  is  no  suitable  space  already
     free.

     _R_e_a_l_l_o_c changes the size of the block pointed to by  _p_t_r  to
     _s_i_z_e  bytes  and  returns  a pointer to the (possibly moved)
     block.  The contents will be unchanged up to the  lesser  of
     the new and old sizes.

     _R_e_a_l_l_o_c also works if _p_t_r points to a block freed since  the
     last  call  of _m_a_l_l_o_c, _r_e_a_l_l_o_c, or _c_a_l_l_o_c; thus sequences of
     _f_r_e_e, _m_a_l_l_o_c and _r_e_a_l_l_o_c can exploit the search strategy  of
     _m_a_l_l_o_c to do storage compaction.

     _C_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.  The space is initialized to zeros.

     Each of the allocation routines returns a pointer  to  space
     suitably  aligned  (after  possible  pointer  coercion)  for
     storage of any type of object.

DIAGNOSTICS
     _M_a_l_l_o_c, _r_e_a_l_l_o_c and _c_a_l_l_o_c return  a  null  pointer  (0)  if
     there  is  no  available  memory  or  if  the arena has been
     detectably corrupted by storing  outside  the  bounds  of  a
     block.   When _r_e_a_l_l_o_c returns 0, the block pointed to by _p_t_r
     may be destroyed.

BUGS
     _F_r_e_e does not check its pointer argument for validity.  When
     passed a null pointer (value 0), it causes a memory fault.