log_target_->pt_->dump();

[ardavan]

what is the meaning of this code?
log_target_->pt_->dump();

[dhayden]

It dereferences log_target_ to get an object.
Then it dereferences the pt_ pointer of that object to get another object.
Then it calls the dump() method of that other object.

Without seeing the rest of the code, I can't tell you what the code accomplishes.