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Message |
Pedja
Guest
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 Posted: Tue Jul 08, 2003 6:55 am Post subject: Using exception object outside try-catch block |
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Hello.
I need to do something like this:
Exception *pe = NULL;
try
{
....
}
catch( Exception &e )
{
....
pe = &e;
....
}
catch( ... )
{
....
}
if ( pe )
{
// use pe
}
In this example, I presume that 'pe' will be dangling pointer outside
try-catch block (if initialized inside).
If I use:
pe = new Exception( e );
instead of:
pe = &e;
this will not do the job, since 'e' could be object of the class
derived from Exception. In that case I couldn't access 'additional'
functionality.
Am I missing something obvious here?
Does anybody have any advise?
Thanks.
- Pedja.
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JKroetch
Guest
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| Posted: Wed Aug 13, 2003 4:33 pm Post subject: Re: Using exception object outside try-catch block |
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"Eivind Midtgård" <see.signature (AT) somewhere (DOT) invalid> wrote
| Quote: |
You want to use the exception outside of the try/catch.
Then the thrown exception must be allocated on the heap,
i.e. you must use "throw new Exception " instead
of "throw Exception". Your catch should
be modified to read "catch (Exception* e)".
(Let me add that it is generally no good idea to
mix references and pointers.)
|
EEEEK! Definitely don't start throwing around allocated exceptions!
You'll be leaking memory like a sieve (cause you'll have to delete
them at all points, etc.) Even with Smart Wrappers to deallocate the
memory, this is not a good idea.
My guess is you're using the exception to pass some kind of
information along? In that case, I'd create a NEW class that takes the
exception in the constructor and gains the pertinent information from
it. You'd end up with this:
(Pseudo-code)
///////////////////////////////////////////
class MyExceptionInfo {
public:
MyExceptionInfo(MyException& e) {
// Copies the data
}
};
/// in code
MyExceptionInfo* pInfo = NULL;
try {
// Throws MyException
GetData();
}
catch (MyException &e) {
pInfo = new MyExceptionInfo(e);
}
if (pInfo != NULL) {
// Exception was thrown!
// Use data!
// Ensure I clean up!
delete pInfo;
pInfo = NULL;
}
///////////////////////////////////////////
Much safer & cleaner. DO NOT DO NOT DO NOT "throw new MyException();"
You've been warned. :)
John
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