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<h4 class="subsection">10.10.3 Classes</h4>
<p><a name="index-class_002c-scope-2039"></a><a name="index-RECORD_005fTYPE-2040"></a><a name="index-UNION_005fTYPE-2041"></a><a name="index-CLASSTYPE_005fDECLARED_005fCLASS-2042"></a><a name="index-TYPE_005fBINFO-2043"></a><a name="index-BINFO_005fTYPE-2044"></a><a name="index-TYPE_005fFIELDS-2045"></a><a name="index-TYPE_005fVFIELD-2046"></a><a name="index-TYPE_005fMETHODS-2047"></a>
Besides namespaces, the other high-level scoping construct in C++ is the
class. (Throughout this manual the term <dfn>class</dfn> is used to mean the
types referred to in the ANSI/ISO C++ Standard as classes; these include
types defined with the <code>class</code>, <code>struct</code>, and <code>union</code>
keywords.)
<p>A class type is represented by either a <code>RECORD_TYPE</code> or a
<code>UNION_TYPE</code>. A class declared with the <code>union</code> tag is
represented by a <code>UNION_TYPE</code>, while classes declared with either
the <code>struct</code> or the <code>class</code> tag are represented by
<code>RECORD_TYPE</code>s. You can use the <code>CLASSTYPE_DECLARED_CLASS</code>
macro to discern whether or not a particular type is a <code>class</code> as
opposed to a <code>struct</code>. This macro will be true only for classes
declared with the <code>class</code> tag.
<p>Almost all non-function members are available on the <code>TYPE_FIELDS</code>
list. Given one member, the next can be found by following the
<code>TREE_CHAIN</code>. You should not depend in any way on the order in
which fields appear on this list. All nodes on this list will be
‘<samp><span class="samp">DECL</span></samp>’ nodes. A <code>FIELD_DECL</code> is used to represent a non-static
data member, a <code>VAR_DECL</code> is used to represent a static data
member, and a <code>TYPE_DECL</code> is used to represent a type. Note that
the <code>CONST_DECL</code> for an enumeration constant will appear on this
list, if the enumeration type was declared in the class. (Of course,
the <code>TYPE_DECL</code> for the enumeration type will appear here as well.)
There are no entries for base classes on this list. In particular,
there is no <code>FIELD_DECL</code> for the “base-class portion” of an
object.
<p>The <code>TYPE_VFIELD</code> is a compiler-generated field used to point to
virtual function tables. It may or may not appear on the
<code>TYPE_FIELDS</code> list. However, back ends should handle the
<code>TYPE_VFIELD</code> just like all the entries on the <code>TYPE_FIELDS</code>
list.
<p>The function members are available on the <code>TYPE_METHODS</code> list.
Again, subsequent members are found by following the <code>TREE_CHAIN</code>
field. If a function is overloaded, each of the overloaded functions
appears; no <code>OVERLOAD</code> nodes appear on the <code>TYPE_METHODS</code>
list. Implicitly declared functions (including default constructors,
copy constructors, assignment operators, and destructors) will appear on
this list as well.
<p>Every class has an associated <dfn>binfo</dfn>, which can be obtained with
<code>TYPE_BINFO</code>. Binfos are used to represent base-classes. The
binfo given by <code>TYPE_BINFO</code> 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
<code>BINFO_N_BASE_BINFOS</code>. The base binfos themselves are obtained
with <code>BINFO_BASE_BINFO</code> and <code>BINFO_BASE_ITERATE</code>. To add a
new binfo, use <code>BINFO_BASE_APPEND</code>. The vector of base binfos can
be obtained with <code>BINFO_BASE_BINFOS</code>, but normally you do not need
to use that. The class type associated with a binfo is given by
<code>BINFO_TYPE</code>. It is not always the case that <code>BINFO_TYPE
(TYPE_BINFO (x))</code>, because of typedefs and qualified types. Neither is
it the case that <code>TYPE_BINFO (BINFO_TYPE (y))</code> is the same binfo as
<code>y</code>. The reason is that if <code>y</code> is a binfo representing a
base-class <code>B</code> of a derived class <code>D</code>, then <code>BINFO_TYPE
(y)</code> will be <code>B</code>, and <code>TYPE_BINFO (BINFO_TYPE (y))</code> will be
<code>B</code> as its own base-class, rather than as a base-class of <code>D</code>.
<p>The access to a base type can be found with <code>BINFO_BASE_ACCESS</code>.
This will produce <code>access_public_node</code>, <code>access_private_node</code>
or <code>access_protected_node</code>. If bases are always public,
<code>BINFO_BASE_ACCESSES</code> may be <code>NULL</code>.
<p><code>BINFO_VIRTUAL_P</code> is used to specify whether the binfo is inherited
virtually or not. The other flags, <code>BINFO_MARKED_P</code> and
<code>BINFO_FLAG_1</code> to <code>BINFO_FLAG_6</code> can be used for language
specific use.
<p>The following macros can be used on a tree node representing a class-type.
<dl>
<dt><code>LOCAL_CLASS_P</code><a name="index-LOCAL_005fCLASS_005fP-2048"></a><dd>This predicate holds if the class is local class <em>i.e.</em> declared
inside a function body.
<br><dt><code>TYPE_POLYMORPHIC_P</code><a name="index-TYPE_005fPOLYMORPHIC_005fP-2049"></a><dd>This predicate holds if the class has at least one virtual function
(declared or inherited).
<br><dt><code>TYPE_HAS_DEFAULT_CONSTRUCTOR</code><a name="index-TYPE_005fHAS_005fDEFAULT_005fCONSTRUCTOR-2050"></a><dd>This predicate holds whenever its argument represents a class-type with
default constructor.
<br><dt><code>CLASSTYPE_HAS_MUTABLE</code><a name="index-CLASSTYPE_005fHAS_005fMUTABLE-2051"></a><dt><code>TYPE_HAS_MUTABLE_P</code><a name="index-TYPE_005fHAS_005fMUTABLE_005fP-2052"></a><dd>These predicates hold for a class-type having a mutable data member.
<br><dt><code>CLASSTYPE_NON_POD_P</code><a name="index-CLASSTYPE_005fNON_005fPOD_005fP-2053"></a><dd>This predicate holds only for class-types that are not PODs.
<br><dt><code>TYPE_HAS_NEW_OPERATOR</code><a name="index-TYPE_005fHAS_005fNEW_005fOPERATOR-2054"></a><dd>This predicate holds for a class-type that defines
<code>operator new</code>.
<br><dt><code>TYPE_HAS_ARRAY_NEW_OPERATOR</code><a name="index-TYPE_005fHAS_005fARRAY_005fNEW_005fOPERATOR-2055"></a><dd>This predicate holds for a class-type for which
<code>operator new[]</code> is defined.
<br><dt><code>TYPE_OVERLOADS_CALL_EXPR</code><a name="index-TYPE_005fOVERLOADS_005fCALL_005fEXPR-2056"></a><dd>This predicate holds for class-type for which the function call
<code>operator()</code> is overloaded.
<br><dt><code>TYPE_OVERLOADS_ARRAY_REF</code><a name="index-TYPE_005fOVERLOADS_005fARRAY_005fREF-2057"></a><dd>This predicate holds for a class-type that overloads
<code>operator[]</code>
<br><dt><code>TYPE_OVERLOADS_ARROW</code><a name="index-TYPE_005fOVERLOADS_005fARROW-2058"></a><dd>This predicate holds for a class-type for which <code>operator-></code> is
overloaded.
</dl>
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