Question

The problem happens with code like this:

#include <cstdlib>
#include <iostream>
#include <stdexcept>

using namespace std;

int main(int argc, char** argv) {

try {
    throw  runtime_error("Message");
} catch (exception e) {
    cout << e.what();
}
return 0;
}

I expect Message to appear. But the result was std::exception. I thought the subclass virtual functions can be called from the superclass reference. How can fix that?

Answer 1

C++ makes an explicit distinction between reference and value copy. Use

catch (const std::exception& e) 

to catch by reference instead of value.