Thread: Variable life cycle

Hello everyone,


In the sample, I am wondering what is the life cycle of variable b_? Could we access variable b_ in catch block?

I have this confusion is because,

1. I think b_ is member variable, and we should be able to access it anywhere in the class itself, so we can access b_ in catch block;

2. I think b_ is declared and initialized in try {} block, and catch exceeds the {} of try, so we can not access b_ in catch block.

Which option is correct?

http://www.gotw.ca/gotw/066.htm

Code:

class C:
{
  B b_;

  C::C()
  try
    : b_( /*...*/ )
  {
  }
  catch( ... )
  {
    // can we access _b here?
  }

};

thanks in advance,
George

If you compile it, you should have your answer.
1 is correct.

_b(...) doesn't declare anything. You need to specify a type to declare it, like this:
B _b;

Thanks cpjust,


It can compile. :-)

Originally Posted by cpjust

If you compile it, you should have your answer.
1 is correct.

_b(...) doesn't declare anything. You need to specify a type to declare it, like this:
B _b;

regards,
George

I agree, thanks anon!

Originally Posted by anon

If b_ failed to be constructed, I don't see how you can access it.

The article seems to say that if you have multiple member objects and one of them fails to be constructed, you cannot access any of them in the catch block and the exception will be automatically rethrown.

regards,
George

I agree, thanks CornedBee!

Originally Posted by CornedBee

The object is in scope, so you can access it; however, the object may or may not have been constructed, so it definitely isn't safe to access it. Accessing an uninitialized object causes undefined behaviour.

regards,
George