Exceptions in Classes

• Functions can be marked with noexcept
  • void foo() noexcept;
  • This means a function will not throw an exception
    • In the implementation of the function.
    • Any functions it calls.
  • If it does, the C++ runtime system forces the program to exit.
• Exceptions in constructors
  • You can throw an exception in a constructor.
    • But the destructor will never be called.
    • So you should clean up any resources you allocate before you throw the exception.
  • But the sub objects will be destroyed.
  • You can even wrap the ctor-initializer in a try block

       MyClass::MyClass() :
       try 
          member1{value}, member2{value}, ... {
          {
              // body of constructor
          }
          catch () {
              throw (something);
          }
    
            

  • This will catch ctor-initializer throws as well as throws in the constructor body.
  • Sub objects will be destroyed by the time the catch block executes.
• Do not allow exceptions to escape from destructors
  • If they do, they may cause program termination.
  • This is because destructors can be called during a stack unwind due to an exception...
  • And clients never call the destructor, so how can they handle the problem.