18.4.2 Implementation-defined attributes

Analogous to pragmas, the set of attributes may be extended by an implementation. All GNAT-defined attributes are described in Implementation Defined Attributes, and these include several that are specifically intended to correspond to other vendors’ Ada 83 attributes. For migrating from VADS, the attribute VADS_Size may be useful. For compatibility with HP Ada 83, GNAT supplies the attributes Bit, Machine_Size and Type_Class.