about dereferencing pointer to incomplete type

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i have worked some hours, but i can't solved it,
so please tell me why?

in the lxhttpd_netbase.h

CSS

/**
  handle read/write callback.
*/
typedef void ( *read_write_cb )( int fd, void *arg );
struct fd_set;
struct timeval;
/**
  a tcp server.
*/
struct tcp_server
{
        // socket: file descriptor
        int fd;
        // fd set
        struct fd_set *fd_readset;
        struct fd_set *fd_writeset;
        struct fd_set *fd_set;
        // max connection
        int max_con;
        // read/write callback
        read_write_cb read_cb;
        read_write_cb write_cb;
        // argument for read/write callback
        void *arg;
};

in the lxhttpd_netbase.c

#include <sys/types.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <stdio.h>
#include <netinet/in.h>
#include <string.h>
#include "lxhttpd_netbase.h"
#include <unistd.h>

/*
  set fd set
*/
static void _server_set_fd( struct tcp_server *server )
{
        memcpy( server->fd_readset->fd_array, server->fd_set->fd_array, sizeof( server->fd_set->fd_array[0] ) * server->fd_set->fd_count );
        server->fd_readset->fd_count = server->fd_set->fd_count;
        memcpy( server->fd_writeset->fd_array, server->fd_set->fd_array, sizeof( server->fd_set->fd_array[0] ) * server->fd_set->fd_count );
        server->fd_writeset->fd_count = server->fd_set->fd_count;
        FD_SET( server->fd, server->fd_readset );
        //FD_SET( server->fd, server->fd_writeset );
}

and when i complier it by gcc -o lxhttpd_netbase -g lxhttpd_netbase.c
it will come out :

VB

lxhttpd_netbase.c: In function ‘_server_set_fd’:
lxhttpd_netbase.c:46: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:46: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:46: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:46: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:47: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:47: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:48: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:48: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:48: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:48: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:49: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:49: error: dereferencing pointer to incomplete type
lxhttpd_netbase.c:50: error: dereferencing pointer to incomplete type

please help me, thank you very much.

i have included the files in the lxhttpd_netbase.h :

XML

#include <sys/types.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <stdio.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>

but it still don't work. thank you

Posted 19-Feb-11 21:44pm

lxlenovostar

Updated 20-Feb-11 3:27am

v4

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2 solutions

Solution 2

if i must use fd_set in this way , i must include "Winsock2.h",
in linux, we can't use fd_cout and fd_array. because fd_set is:

#undef __NFDBITS
#define __NFDBITS       (8 * sizeof(unsigned long))
 
#undef __FD_SETSIZE
#define __FD_SETSIZE    1024
 
#undef __FDSET_LONGS
#define __FDSET_LONGS   (__FD_SETSIZE/__NFDBITS )
typedef struct {
          unsigned long fds_bits [__FDSET_LONGS];
  } fd_set;

Posted 28-Feb-11 18:22pm

lxlenovostar

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OriginalGriff · Accepted Answer · 2011-02-19T22:00:00

Solution 1

Probably, it is the lack of a firm definition of fd_set - your lxhttpd_netbase.h file defines it as:

struct fd_set;

Try to include the file containing the full definition, and the error should disappear.

At the moment, you try to access the server->fd_readset->fd_array etc. elements of your tcp_server structure, but the compiler doesn't know anything about them!

Posted 19-Feb-11 22:00pm

OriginalGriff

Comments

Espen Harlinn 20-Feb-11 8:11am

Good answer :)

lxlenovostar 20-Feb-11 9:19am

i try to include the fowllowing files,but it doesn't work

#include ???
#include ???
#include <stdlib.h>
#include <stdio.h>
#include ???
#include <string.h>
#include <unistd.h>

OriginalGriff 20-Feb-11 9:21am

Would you mind rephrasing that? :laugh:
I suspect that your less than and grater than characters are being swallowed by the HTML: edit your question and add this at teh end in a code block.

Sergey Alexandrovich Kryukov 20-Feb-11 15:19pm

I edited your text. You need to use HTML char entities, not angular brackets (edit again to see source text). You lost three includes (I marked ???) before I had a chance to help it. Please edit again.
--SA

lxlenovostar 20-Feb-11 9:25am

sorry , i will do it .

OriginalGriff 20-Feb-11 10:17am

Thanks: You need to include Winsock2.h according to http://msdn.microsoft.com/en-us/library/ms737873(v=vs.85).aspx

lxlenovostar 20-Feb-11 10:31am

maybe it could work, but i do it on the Linux, i'm still thinking, thanks

Richard MacCutchan 20-Feb-11 10:43am

A simple Google could have found you this page http://linux.die.net/man/3/fd_set

Sergey Alexandrovich Kryukov 20-Feb-11 15:19pm

Should be easy enough, 5.
--SA