Question

Please see the back trace below, I don´t think I have seen this before and I can not find any information in the documentation:

(gdb) bt
#0  0x000000007b44042c in Driver::setRec (this=0x1, message=@0x50)

Answer 1

I can’t find it in documentation, but it looks like this is how gdb displays references to variables. According to backtrace, you were stopped at class method, accepting 1 parameter by reference with the following signature: Driver::setRec(message&).

Update:
It is not explicitly stated about @ in C++ Expressions documentation. The only thing stated is:

In the parameter list shown when gdb displays a frame, the values of
reference variables are not displayed (unlike other variables); this
avoids clutter, since references are often used for large structures.
The address of a reference variable is always shown, unless you have
specified `set print address off’.