Question

Following fails to catch a exception

int *i;  //intentionally uninitialized

try {
      *i = 6;
    }
catch (const runtime_error e) {
      cout << "caught!" << endl;
    }

is it actually catching a runtime error or an exception?

Answer 1

The line *i = 6; does not throw a runtime_error; it results in undefined behavior.

The uninitialized pointer will be dereferenced and your program will try to write the value six to wherever it points (if it points anywhere). This results in undefined behavior. In most cases, this means your program will either crash immediately or will crash later on because you will have corrupted something important in memory.

There is no way to “catch” this sort of error as an exception in standard C++; you need to write your code such that you don’t do things like this.