contiguous block of
heap allocated memory, with the <I>arg_xxx</I> struct at its head,
followed by the storage space for <I>maxcount</I> argument values as
well as an optional private data structure that may be used to hide
internal data from the end-user. If the allocation failed then the
constructor should return NULL.</P>
<PRE CLASS="western">size_t nbytes;
struct arg_xxx *result;

nbytes = sizeof(struct arg_xxx) + sizeof(struct arg_xxx_priv) + maxcount*sizeof(&lt;xxx&gt;) ;
result = (struct arg_xxx*)mal