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<title>GNU Compiler Collection (GCC) Internals: Function Properties</title>
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<a name="Function-Properties"></a>
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<p>
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Previous: <a href="Function-Basics.html#Function-Basics" accesskey="p" rel="prev">Function Basics</a>, Up: <a href="Functions.html#Functions" accesskey="u" rel="up">Functions</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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<a name="Function-Properties-1"></a>
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<h4 class="subsection">10.8.2 Function Properties</h4>
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<a name="index-function-properties"></a>
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<a name="index-statements"></a>
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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>In C, the <code>DECL_CONTEXT</code> for a function maybe another function.
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This representation indicates that the GNU nested function extension
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is in use. For details on the semantics of nested functions, see the
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GCC Manual. The nested function can refer to local variables in its
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containing function. Such references are not explicitly marked in the
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tree structure; back ends must look at the <code>DECL_CONTEXT</code> for the
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referenced <code>VAR_DECL</code>. If the <code>DECL_CONTEXT</code> for the
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referenced <code>VAR_DECL</code> is not the same as the function currently
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being processed, and neither <code>DECL_EXTERNAL</code> nor
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<code>TREE_STATIC</code> hold, then the reference is to a local variable in
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a containing function, and the back end must take appropriate action.
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</p>
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<dl compact="compact">
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<dt><code>DECL_EXTERNAL</code>
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<a name="index-DECL_005fEXTERNAL-1"></a>
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</dt>
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<dd><p>This predicate holds if the function is undefined.
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</p>
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</dd>
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<dt><code>TREE_PUBLIC</code>
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<a name="index-TREE_005fPUBLIC-1"></a>
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</dt>
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<dd><p>This predicate holds if the function has external linkage.
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</p>
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</dd>
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<dt><code>TREE_STATIC</code>
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<a name="index-TREE_005fSTATIC"></a>
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</dt>
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<dd><p>This predicate holds if the function has been defined.
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</p>
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</dd>
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<dt><code>TREE_THIS_VOLATILE</code>
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<a name="index-TREE_005fTHIS_005fVOLATILE"></a>
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</dt>
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<dd><p>This predicate holds if the function does not return normally.
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</p>
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</dd>
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<dt><code>TREE_READONLY</code>
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<a name="index-TREE_005fREADONLY"></a>
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</dt>
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<dd><p>This predicate holds if the function can only read its arguments.
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</p>
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</dd>
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<dt><code>DECL_PURE_P</code>
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<a name="index-DECL_005fPURE_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the function can only read its arguments, but
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may also read global memory.
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</p>
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</dd>
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<dt><code>DECL_VIRTUAL_P</code>
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<a name="index-DECL_005fVIRTUAL_005fP"></a>
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</dt>
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<dd><p>This predicate holds if the function is virtual.
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</p>
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</dd>
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<dt><code>DECL_ARTIFICIAL</code>
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<a name="index-DECL_005fARTIFICIAL-2"></a>
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</dt>
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<dd><p>This macro holds if the function was implicitly generated by the
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compiler, rather than explicitly declared. In addition to implicitly
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generated class member functions, this macro holds for the special
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functions created to implement static initialization and destruction, to
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compute run-time type information, and so forth.
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</p>
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</dd>
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<dt><code>DECL_FUNCTION_SPECIFIC_TARGET</code>
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<a name="index-DECL_005fFUNCTION_005fSPECIFIC_005fTARGET-1"></a>
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</dt>
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<dd><p>This macro returns a tree node that holds the target options that are
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to be used to compile this particular function or <code>NULL_TREE</code> if
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the function is to be compiled with the target options specified on
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the command line.
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</p>
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</dd>
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<dt><code>DECL_FUNCTION_SPECIFIC_OPTIMIZATION</code>
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<a name="index-DECL_005fFUNCTION_005fSPECIFIC_005fOPTIMIZATION-1"></a>
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</dt>
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<dd><p>This macro returns a tree node that holds the optimization options
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that are to be used to compile this particular function or
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<code>NULL_TREE</code> if the function is to be compiled with the
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optimization options specified on the command line.
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</p>
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</dd>
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</dl>
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<hr>
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<div class="header">
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<p>
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Previous: <a href="Function-Basics.html#Function-Basics" accesskey="p" rel="prev">Function Basics</a>, Up: <a href="Functions.html#Functions" accesskey="u" rel="up">Functions</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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