Difference: std::runtime_error vs std::exception()

Question

What is the difference between std::runtime_error and std::exception? What is the appropriate use for each? Why are they different in the first pla

Answer 1

std::exception should be considered (note the considered) the abstract base of the standard exception hierarchy. This is because there is no mechanism to pass in a specific message (to do this you must derive and specialize what()). There is nothing to stop you from using std::exception and for simple applications it may be all you need.

std::runtime_error on the other hand has valid constructors that accept a string as a message. When what() is called a const char pointer is returned that points at a C string that has the same string as was passed into the constructor.

try
{
    if (badThingHappened)
    {
         throw std::runtime_error("Something Bad happened here");
    }
}
catch(std::exception const& e)
{
    std::cout << "Exception: " << e.what() << "\n";
}