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<title>GNU Compiler Collection (GCC) Internals: Functions for C++</title>
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<a name="Functions-for-C_002b_002b"></a>
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<p>
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Next: <a href="Statements-for-C_002b_002b.html#Statements-for-C_002b_002b" accesskey="n" rel="next">Statements for C++</a>, Previous: <a href="Classes.html#Classes" accesskey="p" rel="prev">Classes</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> [<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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</div>
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<hr>
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<a name="Functions-for-C_002b_002b-1"></a>
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<h4 class="subsection">10.10.4 Functions for C++</h4>
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<a name="index-function-1"></a>
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<a name="index-FUNCTION_005fDECL-1"></a>
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<a name="index-OVERLOAD"></a>
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<a name="index-OVL_005fCURRENT"></a>
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<a name="index-OVL_005fNEXT"></a>
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<p>A function is represented by a <code>FUNCTION_DECL</code> node. A set of
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overloaded functions is sometimes represented by an <code>OVERLOAD</code> node.
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</p>
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<p>An <code>OVERLOAD</code> node is not a declaration, so none of the
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‘<samp>DECL_</samp>’ macros should be used on an <code>OVERLOAD</code>. An
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<code>OVERLOAD</code> node is similar to a <code>TREE_LIST</code>. Use
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<code>OVL_CURRENT</code> to get the function associated with an
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<code>OVERLOAD</code> node; use <code>OVL_NEXT</code> to get the next
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<code>OVERLOAD</code> node in the list of overloaded functions. The macros
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<code>OVL_CURRENT</code> and <code>OVL_NEXT</code> are actually polymorphic; you can
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use them to work with <code>FUNCTION_DECL</code> nodes as well as with
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overloads. In the case of a <code>FUNCTION_DECL</code>, <code>OVL_CURRENT</code>
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will always return the function itself, and <code>OVL_NEXT</code> will always
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be <code>NULL_TREE</code>.
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</p>
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<p>To determine the scope of a function, you can use the
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<code>DECL_CONTEXT</code> macro. This macro will return the class
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(either a <code>RECORD_TYPE</code> or a <code>UNION_TYPE</code>) or namespace (a
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<code>NAMESPACE_DECL</code>) of which the function is a member. For a virtual
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function, this macro returns the class in which the function was
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actually defined, not the base class in which the virtual declaration
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occurred.
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</p>
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<p>If a friend function is defined in a class scope, the
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<code>DECL_FRIEND_CONTEXT</code> macro can be used to determine the class in
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which it was defined. For example, in
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</p><div class="smallexample">
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<pre class="smallexample">class C { friend void f() {} };
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</pre></div>
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<p>the <code>DECL_CONTEXT</code> for <code>f</code> will be the
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<code>global_namespace</code>, but the <code>DECL_FRIEND_CONTEXT</code> will be the
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<code>RECORD_TYPE</code> for <code>C</code>.
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</p>
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<p>The following macros and functions can be used on a <code>FUNCTION_DECL</code>:
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</p><dl compact="compact">
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<dt><code>DECL_MAIN_P</code>
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<a name="index-DECL_005fMAIN_005fP"></a>
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</dt>
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<dd><p>This predicate holds for a function that is the program entry point
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<code>::code</code>.
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</p>
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</dd>
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<dt><code>DECL_LOCAL_FUNCTION_P</code>
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<a name="index-DECL_005fLOCAL_005fFUNCTION_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the function was declared at block scope, even
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though it has a global scope.
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</p>
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</dd>
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<dt><code>DECL_ANTICIPATED</code>
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<a name="index-DECL_005fANTICIPATED"></a>
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</dt>
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<dd><p>This predicate holds if the function is a built-in function but its
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prototype is not yet explicitly declared.
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</p>
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</dd>
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<dt><code>DECL_EXTERN_C_FUNCTION_P</code>
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<a name="index-DECL_005fEXTERN_005fC_005fFUNCTION_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the function is declared as an
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‘<code>extern "C"</code>’ function.
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</p>
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</dd>
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<dt><code>DECL_LINKONCE_P</code>
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<a name="index-DECL_005fLINKONCE_005fP"></a>
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</dt>
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<dd><p>This macro holds if multiple copies of this function may be emitted in
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various translation units. It is the responsibility of the linker to
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merge the various copies. Template instantiations are the most common
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example of functions for which <code>DECL_LINKONCE_P</code> holds; G++
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instantiates needed templates in all translation units which require them,
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and then relies on the linker to remove duplicate instantiations.
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</p>
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<p>FIXME: This macro is not yet implemented.
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</p>
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</dd>
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<dt><code>DECL_FUNCTION_MEMBER_P</code>
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<a name="index-DECL_005fFUNCTION_005fMEMBER_005fP"></a>
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</dt>
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<dd><p>This macro holds if the function is a member of a class, rather than a
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member of a namespace.
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</p>
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</dd>
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<dt><code>DECL_STATIC_FUNCTION_P</code>
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<a name="index-DECL_005fSTATIC_005fFUNCTION_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the function a static member function.
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</p>
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</dd>
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<dt><code>DECL_NONSTATIC_MEMBER_FUNCTION_P</code>
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<a name="index-DECL_005fNONSTATIC_005fMEMBER_005fFUNCTION_005fP"></a>
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</dt>
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<dd><p>This macro holds for a non-static member function.
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</p>
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</dd>
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<dt><code>DECL_CONST_MEMFUNC_P</code>
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<a name="index-DECL_005fCONST_005fMEMFUNC_005fP"></a>
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</dt>
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<dd><p>This predicate holds for a <code>const</code>-member function.
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</p>
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</dd>
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<dt><code>DECL_VOLATILE_MEMFUNC_P</code>
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<a name="index-DECL_005fVOLATILE_005fMEMFUNC_005fP"></a>
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</dt>
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<dd><p>This predicate holds for a <code>volatile</code>-member function.
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</p>
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</dd>
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<dt><code>DECL_CONSTRUCTOR_P</code>
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<a name="index-DECL_005fCONSTRUCTOR_005fP"></a>
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</dt>
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<dd><p>This macro holds if the function is a constructor.
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</p>
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</dd>
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<dt><code>DECL_NONCONVERTING_P</code>
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<a name="index-DECL_005fNONCONVERTING_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the constructor is a non-converting constructor.
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</p>
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</dd>
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<dt><code>DECL_COMPLETE_CONSTRUCTOR_P</code>
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<a name="index-DECL_005fCOMPLETE_005fCONSTRUCTOR_005fP"></a>
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</dt>
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<dd><p>This predicate holds for a function which is a constructor for an object
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of a complete type.
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</p>
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</dd>
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<dt><code>DECL_BASE_CONSTRUCTOR_P</code>
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<a name="index-DECL_005fBASE_005fCONSTRUCTOR_005fP"></a>
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</dt>
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<dd><p>This predicate holds for a function which is a constructor for a base
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class sub-object.
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</p>
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</dd>
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<dt><code>DECL_COPY_CONSTRUCTOR_P</code>
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<a name="index-DECL_005fCOPY_005fCONSTRUCTOR_005fP"></a>
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</dt>
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<dd><p>This predicate holds for a function which is a copy-constructor.
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</p>
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</dd>
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<dt><code>DECL_DESTRUCTOR_P</code>
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<a name="index-DECL_005fDESTRUCTOR_005fP"></a>
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</dt>
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<dd><p>This macro holds if the function is a destructor.
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</p>
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</dd>
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<dt><code>DECL_COMPLETE_DESTRUCTOR_P</code>
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<a name="index-DECL_005fCOMPLETE_005fDESTRUCTOR_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the function is the destructor for an object a
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complete type.
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</p>
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</dd>
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<dt><code>DECL_OVERLOADED_OPERATOR_P</code>
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<a name="index-DECL_005fOVERLOADED_005fOPERATOR_005fP"></a>
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</dt>
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<dd><p>This macro holds if the function is an overloaded operator.
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</p>
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</dd>
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<dt><code>DECL_CONV_FN_P</code>
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<a name="index-DECL_005fCONV_005fFN_005fP"></a>
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</dt>
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<dd><p>This macro holds if the function is a type-conversion operator.
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</p>
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</dd>
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<dt><code>DECL_GLOBAL_CTOR_P</code>
|
<a name="index-DECL_005fGLOBAL_005fCTOR_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the function is a file-scope initialization
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function.
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</p>
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</dd>
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<dt><code>DECL_GLOBAL_DTOR_P</code>
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<a name="index-DECL_005fGLOBAL_005fDTOR_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the function is a file-scope finalization
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function.
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</p>
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</dd>
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<dt><code>DECL_THUNK_P</code>
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<a name="index-DECL_005fTHUNK_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the function is a thunk.
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</p>
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<p>These functions represent stub code that adjusts the <code>this</code> pointer
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and then jumps to another function. When the jumped-to function
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returns, control is transferred directly to the caller, without
|
returning to the thunk. The first parameter to the thunk is always the
|
<code>this</code> pointer; the thunk should add <code>THUNK_DELTA</code> to this
|
value. (The <code>THUNK_DELTA</code> is an <code>int</code>, not an
|
<code>INTEGER_CST</code>.)
|
</p>
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<p>Then, if <code>THUNK_VCALL_OFFSET</code> (an <code>INTEGER_CST</code>) is nonzero
|
the adjusted <code>this</code> pointer must be adjusted again. The complete
|
calculation is given by the following pseudo-code:
|
</p>
|
<div class="smallexample">
|
<pre class="smallexample">this += THUNK_DELTA
|
if (THUNK_VCALL_OFFSET)
|
this += (*((ptrdiff_t **) this))[THUNK_VCALL_OFFSET]
|
</pre></div>
|
|
<p>Finally, the thunk should jump to the location given
|
by <code>DECL_INITIAL</code>; this will always be an expression for the
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address of a function.
|
</p>
|
</dd>
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<dt><code>DECL_NON_THUNK_FUNCTION_P</code>
|
<a name="index-DECL_005fNON_005fTHUNK_005fFUNCTION_005fP"></a>
|
</dt>
|
<dd><p>This predicate holds if the function is <em>not</em> a thunk function.
|
</p>
|
</dd>
|
<dt><code>GLOBAL_INIT_PRIORITY</code>
|
<a name="index-GLOBAL_005fINIT_005fPRIORITY"></a>
|
</dt>
|
<dd><p>If either <code>DECL_GLOBAL_CTOR_P</code> or <code>DECL_GLOBAL_DTOR_P</code> holds,
|
then this gives the initialization priority for the function. The
|
linker will arrange that all functions for which
|
<code>DECL_GLOBAL_CTOR_P</code> holds are run in increasing order of priority
|
before <code>main</code> is called. When the program exits, all functions for
|
which <code>DECL_GLOBAL_DTOR_P</code> holds are run in the reverse order.
|
</p>
|
</dd>
|
<dt><code>TYPE_RAISES_EXCEPTIONS</code>
|
<a name="index-TYPE_005fRAISES_005fEXCEPTIONS"></a>
|
</dt>
|
<dd><p>This macro returns the list of exceptions that a (member-)function can
|
raise. The returned list, if non <code>NULL</code>, is comprised of nodes
|
whose <code>TREE_VALUE</code> represents a type.
|
</p>
|
</dd>
|
<dt><code>TYPE_NOTHROW_P</code>
|
<a name="index-TYPE_005fNOTHROW_005fP"></a>
|
</dt>
|
<dd><p>This predicate holds when the exception-specification of its arguments
|
is of the form ‘<code>()</code>’.
|
</p>
|
</dd>
|
<dt><code>DECL_ARRAY_DELETE_OPERATOR_P</code>
|
<a name="index-DECL_005fARRAY_005fDELETE_005fOPERATOR_005fP"></a>
|
</dt>
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<dd><p>This predicate holds if the function an overloaded
|
<code>operator delete[]</code>.
|
</p>
|
</dd>
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</dl>
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<hr>
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<p>
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Next: <a href="Statements-for-C_002b_002b.html#Statements-for-C_002b_002b" accesskey="n" rel="next">Statements for C++</a>, Previous: <a href="Classes.html#Classes" accesskey="p" rel="prev">Classes</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> [<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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