Experimental Physics and
Industrial Control System

Till Straumann <[email protected]> · Tue, 13 Sep 2011 11:39:48 -0500

I wrote a driver class derived from asynMotorController
(which BTW was easy, thanks for the great package).

I would like the driver to be robust in case e.g., of the
absence of e.g., hardware or a serial communication channel.

Hence, my class does something like:

class MyDrv : public asynMotorController {
public:
    MyDrv() : asynMotorController(<parameters go here>)
    {
        status = detect_hardware(<parameters>);
        if ( status ) {
            throw MyException("HW detection failed\n");
        }
    }
};

In my main application I create a driver object

try {
   new MyDrv();
} catch (MyException &e) {
   printf("Unable to create driver: %s\n", e.what());
}

However, if hardware detection fails and the exception
is thrown and subsequently caught then the IOC application
will eventually (later) segfault in asynPortDriver::callbackTask()
(when trying to lock the mutex). It seems that the work
of the superclass constructor(s) (asynMotorController/asynPortDriver/...) is
not properly undone.

No segfault happens if I comment the entire try block
(including the 'new' statement), i.e., if I create no
driver at all (but still load the .db file etc.).

How am I supposed to handle failure in the constructor?

Thanks
-- Till

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System