Re: unexpected exception handler

From:

suresh shenoy <msureshshenoy@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Tue, 8 Jan 2008 05:41:08 -0800 (PST)

Message-ID:

<9d0aec99-3a2a-4977-aa06-0b8ae761df95@i72g2000hsd.googlegroups.com>

On Jan 8, 7:36 am, George2 <george4acade...@yahoo.com> wrote:

Hello everyone,

This question is about when it is allowed to call throw to re-throw
exception -- make the exception re-throw.

I can only think of two situations,

1. in catch block of an exception;
2. in unexpected handler.

For (2), in unexpected handler, since the input parameter is null, so
in order to get the exception information, we need to re-throw it and
catch it to get exception informaiton.

Is my understanding correct? Here is some pseudo code from Bjarne's
book.

[Code]
// suppose throwY is unexpcted handler
void throwY() throw (Yunexpected)
{
try{
throw; // have to re-throw and catch in order to get excep=

tion

information since current input parameter is null and has no exception
information, my understanding correct?
    } catch (Network_exception& p)
    {
        throw (Yunexpected (&p));
    } catch (...)
    {
        throw (Yunexpected (0));
    }}

[/Code]

thanks in advance,
George

George,

   In a design perspective when you have multiple levels of function
calls, you would most likely write a class (holding exception
information) and create an object of this in the nth level and pass it
all the way up and process it at a central location.
As an example,

class myexception {

....
}

void Func_One() {
try
{
    Func_Two();
}
catch(some exception)
{
  do this;
}
...
catch(myexception)
{
  throw;
}
}

void Func_Two() {
try
{
   Func_Three();
}
catch(some exception)
{

}
catch(myexception)
{
  throw;
}
}

void Func_Three() {
try
{
   something;
}

catch(...)
{
   throw new myexception();
}

}

When you encounter a throw the control is passed backed to the calling
function with app info unless there is finally block.

Suresh