Re: passing host name from a structure.

[Jeff Woods <Kazrak+kernel@cesmail.net>]

At 10/6/2004 04:47 PM -0500, Edward Parrilla wrote:
>#define bcopy(a,b,c) strncpy(b,a,c)
>
>    struct sockaddr_in  sa;  /* socket addr. structure           */
>    struct hostent * hp;     /* host entry                       */
>    char *hostname;
>
>hostname=argv[3];
>
>hp=gethostbyname(hostname);  <-- get this error " warning: assignment 
>makes pointer from integer without a cast"

This error looks really peculiar.  IIUC, it's complaining that 
gethostbyname() returns an int (or other ordinal value) which must be 
converted to a pointer for assignment to "hp".  However, on my system "man 
gethostbyname" says "struct hostent *gethostbyname(const char *name);" 
which says it should be returning a pointer (even one of the same type as 
you declared "hp").  Have you declared a prototype for gethostbyname()?  If 
not, then the compiler assumes the function returns an int.  The same man 
page indicates you should include this line in your source:  "#include 
<netdb.h>".  Just to be sure, check "man gethostbyname" on your system and 
see what include files it recommends and what type gethostbyname() 
returns.  If you've confirmed that's not the problem, then you might dig 
into the include file(s), find the prototype being used for gethostbyname() 
and see that it's correct; but that's very unlikely to be the 
problem.  (Someone else would have seen it a long time ago.)

>bcopy((char *)hp->h_addr, (char *)&sa.sin_addr, hp->h_length);  <-- 
>getting  dereferencing pointer to incomplete type

The problem is the precedence of "(char *)hp->h_addr".  The cast "()" and 
indirection "->" operators have equal precedence level and so left-to-right 
order determines precedence, which means you told the compile to access the 
h_addr struct field of what you just told it is a char.  I think you mean 
"(char *)(hp->h_addr)".  Note also that some groups of operators at the 
same precedence level operate left to right [e.g., arithmetic: (a + b - c)] 
and others operate right to left [e.g., assignments: (a *= b +=2)].

--
Jeff Woods <kazrak+kernel@cesmail.net>