Terminate called after throwing an instance of an exception, core dumped

Question

I am going over C++ exceptions and am running into an error that I am unsure of why it is giving me issues:

 #include <iostream>
 #include <exception>

 class err : public std::exception
 {
 public:
      const char* what() const noexcept { return "error"; }
 };

 void f() throw()
 {
      throw err();
 }

 int main()
 {
      try
      {
           f();
      }
      catch (const err& e)
      {
           std::cout << e.what() << std::endl;
      }
 }

When I run it, I get the following runtime error:

 terminate called after throwing an instance of 'err'
   what():  error
 Aborted (core dumped)

If I move the try/catch logic completely to f(), i.e.

 void f() 
 {
      try
      {
           throw err();
      }
      catch (const err& e)
      {
            std::cout << e.what() << std::endl;
      }
 }

And just call it from main (without the try/catch block in main), then there is no error. Am I not understanding something, as it relates to throwing exceptions from functions?

Answer 1

The throw() in void f() throw() is a dynamic exception specification and is deprecated since c++11. It's was supposed to be used to list the exceptions a function could throw. An empty specification (throw()) means there are no exceptions that your function could throw. Trying to throw an exception from such a function calls std::unexpected which, by default, terminates.

Since c++11 the preferred way of specifying that a function cannot throw is to use noexcept. For example void f() noexcept.