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authoralk3pInjection <webmaster@raspii.tech>2024-02-04 16:16:35 +0800
committeralk3pInjection <webmaster@raspii.tech>2024-02-04 16:16:35 +0800
commitabdaadbcae30fe0c9a66c7516798279fdfd97750 (patch)
tree00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gccint/Function-Basics.html
Import stripped Arm GNU Toolchain 13.2.Rel1HEADumineko
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+<head>
+<title>GNU Compiler Collection (GCC) Internals: Function Basics</title>
+
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+<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
+<a name="Function-Basics"></a>
+<div class="header">
+<p>
+Next: <a href="Function-Properties.html#Function-Properties" accesskey="n" rel="next">Function Properties</a>, Up: <a href="Functions.html#Functions" accesskey="u" rel="up">Functions</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>
+</div>
+<hr>
+<a name="Function-Basics-1"></a>
+<h4 class="subsection">11.8.1 Function Basics</h4>
+<a name="index-DECL_005fNAME-1"></a>
+<a name="index-DECL_005fASSEMBLER_005fNAME"></a>
+<a name="index-TREE_005fPUBLIC"></a>
+<a name="index-DECL_005fARTIFICIAL-1"></a>
+<a name="index-DECL_005fFUNCTION_005fSPECIFIC_005fTARGET"></a>
+<a name="index-DECL_005fFUNCTION_005fSPECIFIC_005fOPTIMIZATION"></a>
+
+<p>A function has four core parts: the name, the parameters, the result,
+and the body. The following macros and functions access these parts
+of a <code>FUNCTION_DECL</code> as well as other basic features:
+</p><dl compact="compact">
+<dt><code>DECL_NAME</code>
+<a name="index-DECL_005fNAME-2"></a>
+</dt>
+<dd><p>This macro returns the unqualified name of the function, as an
+<code>IDENTIFIER_NODE</code>. For an instantiation of a function template,
+the <code>DECL_NAME</code> is the unqualified name of the template, not
+something like <code>f&lt;int&gt;</code>. The value of <code>DECL_NAME</code> is
+undefined when used on a constructor, destructor, overloaded operator,
+or type-conversion operator, or any function that is implicitly
+generated by the compiler. See below for macros that can be used to
+distinguish these cases.
+</p>
+</dd>
+<dt><code>DECL_ASSEMBLER_NAME</code>
+<a name="index-DECL_005fASSEMBLER_005fNAME-1"></a>
+</dt>
+<dd><p>This macro returns the mangled name of the function, also an
+<code>IDENTIFIER_NODE</code>. This name does not contain leading underscores
+on systems that prefix all identifiers with underscores. The mangled
+name is computed in the same way on all platforms; if special processing
+is required to deal with the object file format used on a particular
+platform, it is the responsibility of the back end to perform those
+modifications. (Of course, the back end should not modify
+<code>DECL_ASSEMBLER_NAME</code> itself.)
+</p>
+<p>Using <code>DECL_ASSEMBLER_NAME</code> will cause additional memory to be
+allocated (for the mangled name of the entity) so it should be used
+only when emitting assembly code. It should not be used within the
+optimizers to determine whether or not two declarations are the same,
+even though some of the existing optimizers do use it in that way.
+These uses will be removed over time.
+</p>
+</dd>
+<dt><code>DECL_ARGUMENTS</code>
+<a name="index-DECL_005fARGUMENTS"></a>
+</dt>
+<dd><p>This macro returns the <code>PARM_DECL</code> for the first argument to the
+function. Subsequent <code>PARM_DECL</code> nodes can be obtained by
+following the <code>TREE_CHAIN</code> links.
+</p>
+</dd>
+<dt><code>DECL_RESULT</code>
+<a name="index-DECL_005fRESULT"></a>
+</dt>
+<dd><p>This macro returns the <code>RESULT_DECL</code> for the function.
+</p>
+</dd>
+<dt><code>DECL_SAVED_TREE</code>
+<a name="index-DECL_005fSAVED_005fTREE"></a>
+</dt>
+<dd><p>This macro returns the complete body of the function.
+</p>
+</dd>
+<dt><code>TREE_TYPE</code>
+<a name="index-TREE_005fTYPE-5"></a>
+</dt>
+<dd><p>This macro returns the <code>FUNCTION_TYPE</code> or <code>METHOD_TYPE</code> for
+the function.
+</p>
+</dd>
+<dt><code>DECL_INITIAL</code>
+<a name="index-DECL_005fINITIAL-1"></a>
+</dt>
+<dd><p>A function that has a definition in the current translation unit will
+have a non-<code>NULL</code> <code>DECL_INITIAL</code>. However, back ends should not make
+use of the particular value given by <code>DECL_INITIAL</code>.
+</p>
+<p>It should contain a tree of <code>BLOCK</code> nodes that mirrors the scopes
+that variables are bound in the function. Each block contains a list
+of decls declared in a basic block, a pointer to a chain of blocks at
+the next lower scope level, then a pointer to the next block at the
+same level and a backpointer to the parent <code>BLOCK</code> or
+<code>FUNCTION_DECL</code>. So given a function as follows:
+</p>
+<div class="smallexample">
+<pre class="smallexample">void foo()
+{
+ int a;
+ {
+ int b;
+ }
+ int c;
+}
+</pre></div>
+
+<p>you would get the following:
+</p>
+<div class="smallexample">
+<pre class="smallexample">tree foo = FUNCTION_DECL;
+tree decl_a = VAR_DECL;
+tree decl_b = VAR_DECL;
+tree decl_c = VAR_DECL;
+tree block_a = BLOCK;
+tree block_b = BLOCK;
+tree block_c = BLOCK;
+BLOCK_VARS(block_a) = decl_a;
+BLOCK_SUBBLOCKS(block_a) = block_b;
+BLOCK_CHAIN(block_a) = block_c;
+BLOCK_SUPERCONTEXT(block_a) = foo;
+BLOCK_VARS(block_b) = decl_b;
+BLOCK_SUPERCONTEXT(block_b) = block_a;
+BLOCK_VARS(block_c) = decl_c;
+BLOCK_SUPERCONTEXT(block_c) = foo;
+DECL_INITIAL(foo) = block_a;
+</pre></div>
+
+</dd>
+</dl>
+
+
+<hr>
+<div class="header">
+<p>
+Next: <a href="Function-Properties.html#Function-Properties" accesskey="n" rel="next">Function Properties</a>, Up: <a href="Functions.html#Functions" accesskey="u" rel="up">Functions</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>
+</div>
+
+
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+</html>