Incompatible Pointer Type warnings

[trillianjedi]

Hi all,

I'm using a piece of code from a book (Linux Programming) which includes some IPC related excerpts I'd like to use (queue stuff).

Here's some code that I'm using from the book, which produces the below compiler warnings.

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <string.h>
#include <sys/ipc.h>

/* Get a queue DS record */
int getQueueDs( int qid, struct msgqid_ds *qbuf ) {
	if( msgctl( qid, IPC_STAT, qbuf) == -1) {
		return(0);
	}
	return(1);
}

/* Change queue Permissions */
int changeQueuePerms( int qid, char *mode ) {
	struct msqid_ds tmpbuf;

	/* Retrieve a current copy of the internal data structure */
	getQueueDs(qid, &tmpbuf);

	/* Change the permissions using an old trick */
	sscanf(mode, "&#37;ho", &tmpbuf.msg_perm.mode);

	/* Update the internal data structure */
	if( msgctl( qid, IPC_SET, &tmpbuf) == -1) {
		return(0);
	}

	return(1);
}

/* Change queue Size */
int changeQueueSize( int qid, ushort newSize ) {
	struct msqid_ds tmpbuf;

	/* Retrieve a current copy of the internal data structure */
	getQueueDs(qid, &tmpbuf);

	/* Change the size value */
	tmpbuf.msg_qbytes = newSize;

	/* Update the internal data structure */
	if( msgctl( qid, IPC_SET, &tmpbuf) == -1) {
		return(0);
	}

	return(1);
}

/* Get queue info */
int getQueueNumberOfMessages( int qid ) {
	struct msqid_ds tmpbuf;

	/* Retrieve a current copy of the internal data structure */
	if ( getQueueDs( qid, &tmpbuf) ) {
		return(tmpbuf.msg_qnum);
	}

	return(-1);
}

Compiler Warnings:-

includes/queues.h:47: warning: `struct msgqid_ds' declared inside parameter list
includes/queues.h:47: warning: its scope is only this definition or declaration, which is probably not what you want
includes/queues.h: In function `getQueueDs':
includes/queues.h:48: warning: passing arg 3 of `msgctl' from incompatible pointer type
includes/queues.h: In function `changeQueuePerms':
includes/queues.h:59: warning: passing arg 2 of `getQueueDs' from incompatible pointer type
includes/queues.h: In function `changeQueueSize':
includes/queues.h:77: warning: passing arg 2 of `getQueueDs' from incompatible pointer type
includes/queues.h: In function `getQueueNumberOfMessages':
includes/queues.h:95: warning: passing arg 2 of `getQueueDs' from incompatible pointer type

I don't understand the incompatible pointer type warning as the man page tells me that these are the correct types for the msgctl function:-

int msgctl(int msqid, int cmd, struct msqid_ds *buf);

The "struct declared inside parameter list" warning I just don't follow at all.

Any thoughts?

Many thanks.

[tabstop]

Yours: struct msgqid_ds *
Theirs: struct msqid_ds *

Compare and contrast.

[rags_to_riches]

EDIT: Oooo...good eye, tabstop.

[trillianjedi]

Ouch

Thank you - great spot.......