Program errors cannot be solved after being found online for a long time

For program errors, I cannot find a solution for a long time on the Internet-Linux general technology-Linux technology and application information. The following is a detailed description. When I compile the following program, the compilation fails.

# Include "unistd. h"
# Include "stdlib. h"
# Include "stdio. h"
# Include
# Include
# Include



Int
Main (int argc, char ** argv)
{
Intmqid;
Size_tlen;
Longint type;
Struct msgbuf * ptr;

If (argc! = 5)
Fprintf (stderr, "usage: msgsnd <# Bytes> Data ");
Len = atoi (argv [2]);
Type = atoi (argv [3]);

Mqid = msgget (ftok (argv [1], 0), 0200 );

Ptr = calloc (sizeof (long) + len, sizeof (char ));
Ptr-> mtype = type; // 26 rows
Ptr-> mtext = argv [4]; // 27 rows

Msgsnd (mqid, ptr, len, 0 );

Exit (0 );
}

The following errors always occur:


[Root @ localhost ch6msg] # gcc msgsnd. c-o msgsnd
Msgsnd. c: In the 'main' function:
Msgsnd. c: 26: Error: Leading pointer to incomplete type
Msgsnd. c: 27: Error: Leading pointer to incomplete type

Which of the following experts can help solve the problem?