Some questions about qdebug, a custom debug and const approach

[high_flyer]

frankly, I have no idea what you are after, and why you make it so complicated.
So far I have seen nothing in what you have posted, that qDebug() does not give you since you only output strings.
Its your job to convert what ever other types to strings, and then you can just feed the strings to qDebug().
You are over complicating a non existing problem (in my view).

gives me :
123456
and I'd want
123
456

Well, then put a line break where you need it!
qDebug() will output any string you give it, so just create the string you want the way you want it.

Perhaps this can hellp :
Cout needs to receive and endl because if not there is no line feed.
cout<<"hello"<<"how are you"<<endl;
But qDebug NOT :
qDebug()<<"hello"<<"how are you";
SO ..... what kind of magic is there in qDebug ?

Thats is true, qDebug() adds a line break after every srting, it not magic, just the way it was conceived.
As the qDebug() docs states:

With this syntax, the function returns a QDebug object that is configured to use the QtDebugMsg message type. It automatically puts a single space between each item, and outputs a newline at the end. It supports many C++ and Qt types.

[tonnot]

My job is not to convert all to strings ....

As you has written :

.... and outputs a newline at the end.

This is the main question, How qDebug do it ? How it knows that there is an end ?
Thanks

[high_flyer]

My job is not to convert all to strings

Ok, if you say so.

How qDebug do it ?

It just appends an '\n' to any string it gets as input.

You can look in the qDebug() code to see exactly how.

You might want to read the QDebug docs.

[tonnot]

Solved.
The way is to do it at destructor.....