Into the Void

[Scott <drmemory@3rivers.net>]

Years ago, I learned this trick from somebody in the C/C++ Journal, or
whatever that rag was called:

           memcpy(*data_buf,bp,len)[len] = '\0';

I get the following error:

indatax.c: In function `read_datum':
indatax.c:374: warning: dereferencing `void *' pointer
indatax.c:374: invalid use of void expression

and if I cast the function:

           (char *) memcpy(*data_buf,bp,len)[len] = '\0';

I get:

indatax.c: In function `read_datum':
indatax.c:374: warning: dereferencing `void *' pointer
indatax.c:374: void value not ignored as it ought to be

What aren't I understanding here? Tell me to go away if these
questions are too elementary for the list....