E2457 Delphi style classes must be caught by reference (C++)
Go Up to Compiler Errors And Warnings (C++) Index
You can only catch a Delphi style object by pointer. Delphi style classes derive directly or indirectly from System::TObject.
Example:
void foo(TObject *p) { try { throw(p); } catch (TObject o) // Error { } catch (TObject *op) // OK { } }