NSMutableString append data error

Question

I have AsyncSocket like this.

- (void)onSocket:(AsyncSocket *)sock didReadData:(NSData *)data withTag:(long)tag {
NSString *message = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];
[data getBytes:&tdata];
  if (tdata > 5) {

    if(bheader){
        if(!charS){
            if([message isEqualToString:@"S"]){
                CMSG = message;
                charS=YES;
            }
        }
        else{
            NSMutableString *tmp = [[NSMutableString alloc] initWithString:@""];
            [tmp appendString:CMSG];       <<<<< This is code error at loop 2, 
            [tmp appendString:message];     the first loop success but second is fail
            CMSG = tmp;
            [tmp release];
        }
    }
    else{  
        if (message){            
            cmessage = [[NSString alloc]initWithFormat:@"%@%@",cmessage,message]  ;
        }
        else
            NSLog(@"Error converting received data into UTF-8 String");

        cdata++;
        if(cdata==idata) {
            msgComplete=YES;
        }

    }

    if (msgComplete) {
        NSDictionary *userInfo = [NSDictionary dictionaryWithObject:cmessage forKey:kNotificationMessage];
        [notificationCenter postNotificationName:kNotification object:self userInfo:userInfo];
        cmessage=@"";
        CMSG=@"";
        msgComplete=NO;
        bheader=YES;
        cdata=0;
        charS=NO;
        [cmessage release];

    }
}

[sock readDataToLength:1 withTimeout:-1 tag:0];

}

This code fail at second loop at [tmp appendString:CMSG]; Thread 1: Program received signal "SIGABRT"
How fix this error ?
Thanks gurus,

Answer 1

CMSG is assigned to tmp but tmp is released right afterwards. CMSG needs to be retained throughout the loop.

CMSG = tmp;   //<< should be CMSG = [tmp retain];
[tmp release];

Now you have another potential problem. You are using a deprecated method here

[data getBytes:&tdata];
  if (tdata > 5) {

getBytes: was deprecated because of a potential buffer overrun and the result of getBytes is not appropriate to use for if(tdata > 5) . If you want to check the length of bytes get that that from the NSData object.

Answer 2

I see an error that may or may not be the ultimate problem here. In the final conditional statement, you have:

cmessage=@"";
...
[cmessage release];

I don't think you should be releasing that string. I don't actually know all of the ins and outs of NSString objects that are defined in that way (as opposed to stringWithFormat: or initWithString: ), but I don't think that you have ownership of that string object. You shouldn't have to release it.

Remove that release message and see if it helps.