Question

This is a picky thing and it is probably just my OCD flairing up but I was wondering why the standard exception class hierarchy is set up as it is.

exception
  bad_alloc
  bad_cast
  bad_typeid
  bad_exception
  ios_base::failure
  runtime_error
    subclasses...
  logic_error
    subclasses...

Couldn’t all the bad_* exceptions just be subclasses of something like lang_support_error? And ios_base::failure seems completely out of place.

Is there some historical or technical reasons the hierachy ended up like this?

Answer 1

If I remember correctly, the logic was:

• logic_error would be the equivalent of an assert, but with less drastic behavior
• runtime_error would be the base of all others

However, as you noticed, it does not quite hold, even in the standard library itself.

The main issue I guess is subjectivity: is std::out_of_range a logic_error or a runtime_error ?

It’s subjective…