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

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;

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.

     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, grave 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_e_a_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

Printed 9/10/82                                                 1

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

     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.  _M_a_l_l_o_c may be recompiled to check the arena very
     stringently on every transaction; see the source code.

BUGS
     When _r_e_a_l_l_o_c returns 0, the block pointed to by _p_t_r may be
     destroyed.

Printed 9/10/82                                                 2