Are there cases where a typedef is absolutely necessary?

Question

Consider the following excerpt from the safe bool idiom:

typedef void (Testable::*bool_type)() const;
operator bool_type() const;

Is it possibl

Answer 1

One case (unrelated to your question) where a typedef is required is when using the

va_arg() macro. Quoting the C99 standard (7.15.1.1):

type* va_arg(va_list ap, type);

...

The parameter type shall be a type name specified such that the type of a pointer to an object that has the specified type can be obtained simply by postfixing a * to type