Error: invalid lvalue in assignment

xxrsc · 08-14-2006, 06:15 PM

I'm trying to compile irmp3-v0.5.6 but I have the following error.

irmp3mod.c: In function ‘mod_sendmsg’:
irmp3mod.c:103: error: invalid lvalue in assignment
make[2]: *** [irmp3mod.o] Error 1

Here's where I think the problem is:

Code:

// append message to queue
	for (m=mod_msgs; m && m->next; m=m->next);
	m ? m->next : mod_msgs = newmsg;

Here's the function:

Code:

void mod_sendmsg (int msgtype, char *msg)
{
	mod_message_t *newmsg, *m;
	log_printf(LOG_NOISYDEBUG,"CORE: message %s type %d sent",msg,msgtype);
	if(answer_head) { // we are in a query
		// the action has to be taken immediatly, so transform this to a query call
		// however, we don't care about the answer
		free_message(mod_query(msgtype,msg));
		// create new message entry
		newmsg = malloc(sizeof(mod_message_t));
		if (!newmsg) {
			return;
		}
		newmsg->msg = malloc(strlen(msg)+1);
		if (!newmsg->msg) {
			free(newmsg);
			return;
		}
		newmsg->msgtype = msgtype;
		strcpy(newmsg->msg, msg);
		newmsg->next = NULL;
		answer_head->next = newmsg;
		answer_head = newmsg;
		return;
	}

	// create new message entry
	newmsg = malloc(sizeof(mod_message_t));
	if (!newmsg)
		return;
	newmsg->msg = malloc(strlen(msg)+1);
	if (!newmsg->msg) {
		free(newmsg);
		return;
	}
	newmsg->msgtype = msgtype;
	strcpy(newmsg->msg, msg);
	newmsg->next = NULL;

	// append message to queue
	for (m=mod_msgs; m && m->next; m=m->next);
	m ? m->next : mod_msgs = newmsg;
}

I've tried using and older version of gcc but then I get a bunch of other errors.

helmut_hed · 08-17-2006, 01:43 PM

That code is maybe a little too "clever"

I would first look at the type of m->next and mod_msgs and make sure they are still the same as the type of newmsg. If they are, I would try rewriting this line:

m ? m->next : mod_msgs = newmsg;

as this:

if (m) {
m->next = newmsg;
}
else {
mod_msgs = newmsg;
}

which should be equivalent. "invalid lvalue" means the left-hand-side of an assignment (the lvalue) is messed up. It could be a gcc version issue as you surmised.

Good luck,
Jeff