C + + Exception object

1.catch clause argument is an object

Look at the code first:

#include <iostream> #include <exception>using namespace Std;class myexception:p ublic exception{public: MyException () {cout<< "myexception ()" &LT;&LT;ENDL;} ~myexception () {cout<< "~myexception ()" &LT;&LT;ENDL;} MyException (const myexception& RHS) {cout<< "myexception (const myexception& RHS)" &LT;&LT;ENDL;} void what () {cout<< "MyException What ()" <<endl;}}; Class Derivedexception:public myexception{public:derivedexception () {cout<< "derivedexception ()" <<endl ;} ~derivedexception () {cout<< "~derivedexception ()" &LT;&LT;ENDL;} A derived class that does not display a copy constructor that calls the base class implicitly calls the base class's default constructor derivedexception (const derivedexception& RHS): MyException (RHS) {cout << "derivedexception (const derivedexception& RHS)" &LT;&LT;ENDL;} void what () {cout<< "derivedexception What ()" <<endl;}}; void Exceptiontest () {Try{throw derivedexception ();//This is not a local object and does not destroy}catch (MyException ex) with Exceptiontest () Ex.what (); throw; The original exception object was re-thrown; }}int Main () {Try{exceptionteSt ();} catch (Derivedexception ex) {ex.what ();} return 0;}

Program Run Result:

2. When the catch clause is a reference parameter

The code is as follows:

#include <iostream> #include <exception>using namespace Std;class myexception:p ublic exception{public: MyException () {cout<< "myexception ()" &LT;&LT;ENDL;} ~myexception () {cout<< "~myexception ()" &LT;&LT;ENDL;} MyException (const myexception& RHS) {cout<< "myexception (const myexception& RHS)" &LT;&LT;ENDL;} void what () {cout<< "MyException What ()" <<endl;}}; Class Derivedexception:public myexception{public:derivedexception () {cout<< "derivedexception ()" <<endl ;} ~derivedexception () {cout<< "~derivedexception ()" &LT;&LT;ENDL;} A derived class that does not display a copy constructor that calls the base class implicitly calls the base class's default constructor derivedexception (const derivedexception& RHS): MyException (RHS) {cout << "derivedexception (const derivedexception& RHS)" &LT;&LT;ENDL;} void what () {cout<< "derivedexception What ()" <<endl;}}; void Exceptiontest () {Try{throw derivedexception ();//This is not a local object and will not be destroyed with Exceptiontest ()}catch (MyException & Ex) {ex.what (); throw;//If a change is made to ex, the change is propagated to the next catch clause}}int main () {TRY{exceptiontest ();} catch (Derivedexception &ex) {ex.what ();} return 0;}

The results of the program run as follows:

C + + Exception object