> i was compiling ncbi toolkit, in the file ncbimsg.c  gave a compile-time
> error as <sys/types.h> does not
> include definitions for fd_set . I included the  header file
<sys/types.h>,
> and still give the compilation error as
>
> " 'fd_set' undeclared (  first use in this function )"
AFAIK fd_set is declared in sys/types.h:

typedef struct fd_set {
 __fd_mask fds_bits[__howmany(FD_SETSIZE, __NFDBITS)];
} fd_set;

I think it must be a source code error.