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Next: <a href="Functions-for-C_002b_002b.html#Functions-for-C_002b_002b" accesskey="n" rel="next">Functions for C++</a>, Previous: <a href="Namespaces.html#Namespaces" accesskey="p" rel="prev">Namespaces</a>, Up: <a href="C-and-C_002b_002b-Trees.html#C-and-C_002b_002b-Trees" accesskey="u" rel="up">C and C++ Trees</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Classes-1"></a>
<h4 class="subsection">11.10.3 Classes</h4>
<a name="index-class_002c-scope"></a>
<a name="index-RECORD_005fTYPE-1"></a>
<a name="index-UNION_005fTYPE-1"></a>
<a name="index-CLASSTYPE_005fDECLARED_005fCLASS"></a>
<a name="index-TYPE_005fBINFO"></a>
<a name="index-BINFO_005fTYPE"></a>
<a name="index-TYPE_005fFIELDS-2"></a>
<a name="index-TYPE_005fVFIELD"></a>

<p>Besides namespaces, the other high-level scoping construct in C++ is the
class.  (Throughout this manual the term <em>class</em> 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>
<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>
<p>Almost all 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
&lsquo;<samp>DECL</samp>&rsquo; 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 &ldquo;base-class portion&rdquo; of an
object.  If a function member is overloaded, each of the overloaded
functions appears; no <code>OVERLOAD</code> nodes appear on the <code>TYPE_FIELDS</code>
list.  Implicitly declared functions (including default constructors,
copy constructors, assignment operators, and destructors) will appear on
this list as well.
</p>
<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>
<p>Every class has an associated <em>binfo</em>, 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>
<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>
<p><code>BINFO_VIRTUAL_P</code> is used to specify whether the binfo is inherited
virtually or not.  The other flags, <code>BINFO_FLAG_0</code> to
<code>BINFO_FLAG_6</code>, can be used for language specific use.
</p>
<p>The following macros can be used on a tree node representing a class-type.
</p>
<dl compact="compact">
<dt><code>LOCAL_CLASS_P</code>
<a name="index-LOCAL_005fCLASS_005fP"></a>
</dt>
<dd><p>This predicate holds if the class is local class <em>i.e.</em> declared
inside a function body.
</p>
</dd>
<dt><code>TYPE_POLYMORPHIC_P</code>
<a name="index-TYPE_005fPOLYMORPHIC_005fP"></a>
</dt>
<dd><p>This predicate holds if the class has at least one virtual function
(declared or inherited).
</p>
</dd>
<dt><code>TYPE_HAS_DEFAULT_CONSTRUCTOR</code>
<a name="index-TYPE_005fHAS_005fDEFAULT_005fCONSTRUCTOR"></a>
</dt>
<dd><p>This predicate holds whenever its argument represents a class-type with
default constructor.
</p>
</dd>
<dt><code>CLASSTYPE_HAS_MUTABLE</code>
<a name="index-CLASSTYPE_005fHAS_005fMUTABLE"></a>
</dt>
<dt><code>TYPE_HAS_MUTABLE_P</code>
<a name="index-TYPE_005fHAS_005fMUTABLE_005fP"></a>
</dt>
<dd><p>These predicates hold for a class-type having a mutable data member.
</p>
</dd>
<dt><code>CLASSTYPE_NON_POD_P</code>
<a name="index-CLASSTYPE_005fNON_005fPOD_005fP"></a>
</dt>
<dd><p>This predicate holds only for class-types that are not PODs.
</p>
</dd>
<dt><code>TYPE_HAS_NEW_OPERATOR</code>
<a name="index-TYPE_005fHAS_005fNEW_005fOPERATOR"></a>
</dt>
<dd><p>This predicate holds for a class-type that defines
<code>operator new</code>.
</p>
</dd>
<dt><code>TYPE_HAS_ARRAY_NEW_OPERATOR</code>
<a name="index-TYPE_005fHAS_005fARRAY_005fNEW_005fOPERATOR"></a>
</dt>
<dd><p>This predicate holds for a class-type for which
<code>operator new[]</code> is defined.
</p>
</dd>
<dt><code>TYPE_OVERLOADS_CALL_EXPR</code>
<a name="index-TYPE_005fOVERLOADS_005fCALL_005fEXPR"></a>
</dt>
<dd><p>This predicate holds for class-type for which the function call
<code>operator()</code> is overloaded.
</p>
</dd>
<dt><code>TYPE_OVERLOADS_ARRAY_REF</code>
<a name="index-TYPE_005fOVERLOADS_005fARRAY_005fREF"></a>
</dt>
<dd><p>This predicate holds for a class-type that overloads
<code>operator[]</code>
</p>
</dd>
<dt><code>TYPE_OVERLOADS_ARROW</code>
<a name="index-TYPE_005fOVERLOADS_005fARROW"></a>
</dt>
<dd><p>This predicate holds for a class-type for which <code>operator-&gt;</code> is
overloaded.
</p>
</dd>
</dl>

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Next: <a href="Functions-for-C_002b_002b.html#Functions-for-C_002b_002b" accesskey="n" rel="next">Functions for C++</a>, Previous: <a href="Namespaces.html#Namespaces" accesskey="p" rel="prev">Namespaces</a>, Up: <a href="C-and-C_002b_002b-Trees.html#C-and-C_002b_002b-Trees" accesskey="u" rel="up">C and C++ Trees</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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