Error message: The Application crashed

[josecarlosmissias]

Hello
I created a small application using QTcpServer for sending remote messages when I compile using QT Creator in debug mode the application runs correctly.
When I build configuring QT Creator to release the program crashes and is shown the following error message "image attached".

I wrote a few lines: "qDebug () <<" msg ..."" in some parts of the program:

...
qDebug() << "6. here OK "; far is correct, this message is displayed on the console

if( msg == SAP_RETR_WELCOME_STRING) {
}

qDebug() << "7. here OK "; this message does not show in console

if I try to print the contents of the msg variable, the program crashes:
qDebug () << "contents of msg is. .." << msg;