Possible Duplicate:
catch exception by pointer in C++
What is the best way to catch an exception: by value, reference or pointer and why?
Possible Duplicate:
catch exception by pointer in C++
What is the best way to catch an exception: by value, reference or pointer and why?
You nearly always want to catch exceptions by (usually const) reference.
You dont want to raise any more exceptions so catching by reference is best
By reference, unless you're doing Windows programming, where exceptions are typically caught by pointer.