If you specify a class type for the argument of a catch block (the exception_declaration), the compiler uses a copy constructor to initialize that argument. If that argument does not have a name, the compiler initializes a temporary object and destroys it when the handler exits.
The ISO C++ specifications do not require the compiler to construct temporary objects in cases where they are redundant. The compiler takes advantage of this rule to create more efficient, optimized code. Take this into consideration when debugging your programs, especially for memory problems.