Improved C++ Support in GCC 3.0

• Improvements:
  • G++ now supports importing member functions from base classes with a using-declaration.
  • G++ now enforces access control for nested types.
  • In some obscure cases, functions with the same type could have the same mangled name. This bug caused compiler crashes, link-time clashes, and debugger crashes. Fixing this bug required breaking ABI compatibility for the functions involved. The functions in questions are those whose types involve non-type template arguments whose mangled representations require more than one digit.
  • Certain invalid conversions that were previously accepted will now be rejected. For example, assigning function pointers of one type to function pointers of another type now requires a cast, whereas previously G++ would sometimes accept the code even without the cast.
• Removed (no longer supported):
  • Support for guiding declarations has been removed.
  • Support for assignment to this has been removed. This idiom was used in the very early days of C++, before users were allowed to overload operator new; it is no longer allowed by the C++ standard.
  • Support for signatures, a G++ extension, has been removed.
  • G++ previously allowed sizeof (X::Y) where Y was a non-static member of X, even if the `sizeof' expression occurred outside of a non-static member function of X (or one of its derived classes, or a member-initializer for X or one of its derived classes.) This extension has been removed.
  • G++ no longer allows you to overload the conditional operator (i.e., the ?: operator.)
  • The "named return value" extension:

    int f () return r { r = 3; }

    has been deprecated, and will be removed in a future version of G++.