11.10.3 Classes

Besides namespaces, the other high-level scoping construct in C++ is the class. (Throughout this manual the term class is used to mean the types referred to in the ANSI/ISO C++ Standard as classes; these include types defined with the class, struct, and union keywords.)

A class type is represented by either a RECORD_TYPE or a UNION_TYPE. A class declared with the union tag is represented by a UNION_TYPE, while classes declared with either the struct or the class tag are represented by RECORD_TYPEs. You can use the CLASSTYPE_DECLARED_CLASS macro to discern whether or not a particular type is a class as opposed to a struct. This macro will be true only for classes declared with the class tag.

Almost all members are available on the TYPE_FIELDS list. Given one member, the next can be found by following the TREE_CHAIN. You should not depend in any way on the order in which fields appear on this list. All nodes on this list will be ‘DECL’ nodes. A FIELD_DECL is used to represent a non-static data member, a VAR_DECL is used to represent a static data member, and a TYPE_DECL is used to represent a type. Note that the CONST_DECL for an enumeration constant will appear on this list, if the enumeration type was declared in the class. (Of course, the TYPE_DECL for the enumeration type will appear here as well.) There are no entries for base classes on this list. In particular, there is no FIELD_DECL for the “base-class portion” of an object. If a function member is overloaded, each of the overloaded functions appears; no OVERLOAD nodes appear on the TYPE_FIELDS list. Implicitly declared functions (including default constructors, copy constructors, assignment operators, and destructors) will appear on this list as well.

The TYPE_VFIELD is a compiler-generated field used to point to virtual function tables. It may or may not appear on the TYPE_FIELDS list. However, back ends should handle the TYPE_VFIELD just like all the entries on the TYPE_FIELDS list.

Every class has an associated binfo, which can be obtained with TYPE_BINFO. Binfos are used to represent base-classes. The binfo given by TYPE_BINFO is the degenerate case, whereby every class is considered to be its own base-class. The base binfos for a particular binfo are held in a vector, whose length is obtained with BINFO_N_BASE_BINFOS. The base binfos themselves are obtained with BINFO_BASE_BINFO and BINFO_BASE_ITERATE. To add a new binfo, use BINFO_BASE_APPEND. The vector of base binfos can be obtained with BINFO_BASE_BINFOS, but normally you do not need to use that. The class type associated with a binfo is given by BINFO_TYPE. It is not always the case that BINFO_TYPE (TYPE_BINFO (x)), because of typedefs and qualified types. Neither is it the case that TYPE_BINFO (BINFO_TYPE (y)) is the same binfo as y. The reason is that if y is a binfo representing a base-class B of a derived class D, then BINFO_TYPE (y) will be B, and TYPE_BINFO (BINFO_TYPE (y)) will be B as its own base-class, rather than as a base-class of D.

The access to a base type can be found with BINFO_BASE_ACCESS. This will produce access_public_node, access_private_node or access_protected_node. If bases are always public, BINFO_BASE_ACCESSES may be NULL.

BINFO_VIRTUAL_P is used to specify whether the binfo is inherited virtually or not. The other flags, BINFO_FLAG_0 to BINFO_FLAG_6, can be used for language specific use.

The following macros can be used on a tree node representing a class-type.


This predicate holds if the class is local class i.e. declared inside a function body.


This predicate holds if the class has at least one virtual function (declared or inherited).


This predicate holds whenever its argument represents a class-type with default constructor.


These predicates hold for a class-type having a mutable data member.


This predicate holds only for class-types that are not PODs.


This predicate holds for a class-type that defines operator new.


This predicate holds for a class-type for which operator new[] is defined.


This predicate holds for class-type for which the function call operator() is overloaded.


This predicate holds for a class-type that overloads operator[]


This predicate holds for a class-type for which operator-> is overloaded.