10.10.3 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 non-function 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.

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.

The function members are available on the TYPE_METHODS list. Again, subsequent members are found by following the TREE_CHAIN field. If a function is overloaded, each of the overloaded functions appears; no OVERLOAD nodes appear on the TYPE_METHODS list. Implicitly declared functions (including default constructors, copy constructors, assignment operators, and destructors) will appear on this list as well.

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_MARKED_P and BINFO_FLAG_1 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.

LOCAL_CLASS_P

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

TYPE_POLYMORPHIC_P

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

TYPE_HAS_DEFAULT_CONSTRUCTOR

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

CLASSTYPE_HAS_MUTABLE

TYPE_HAS_MUTABLE_P

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

CLASSTYPE_NON_POD_P

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

TYPE_HAS_NEW_OPERATOR

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

TYPE_HAS_ARRAY_NEW_OPERATOR

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

TYPE_OVERLOADS_CALL_EXPR

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

TYPE_OVERLOADS_ARRAY_REF

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

TYPE_OVERLOADS_ARROW

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