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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gccint/Working-with-declarations.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
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diff --git a/share/doc/gccint/Working-with-declarations.html b/share/doc/gccint/Working-with-declarations.html new file mode 100644 index 0000000..4c7fc8e --- /dev/null +++ b/share/doc/gccint/Working-with-declarations.html @@ -0,0 +1,240 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(a) The FSF's Front-Cover Text is: + +A GNU Manual + +(b) The FSF's Back-Cover Text is: + +You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>GNU Compiler Collection (GCC) Internals: Working with declarations</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Working with declarations"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Working with declarations"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Declarations.html#Declarations" rel="up" title="Declarations"> +<link href="Internal-structure.html#Internal-structure" rel="next" title="Internal structure"> +<link href="Declarations.html#Declarations" rel="previous" title="Declarations"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Working-with-declarations"></a> +<div class="header"> +<p> +Next: <a href="Internal-structure.html#Internal-structure" accesskey="n" rel="next">Internal structure</a>, Up: <a href="Declarations.html#Declarations" accesskey="u" rel="up">Declarations</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> +</div> +<hr> +<a name="Working-with-declarations-1"></a> +<h4 class="subsection">11.4.1 Working with declarations</h4> + +<p>Some macros can be used with any kind of declaration. These include: +</p><dl compact="compact"> +<dt><code>DECL_NAME</code> +<a name="index-DECL_005fNAME"></a> +</dt> +<dd><p>This macro returns an <code>IDENTIFIER_NODE</code> giving the name of the +entity. +</p> +</dd> +<dt><code>TREE_TYPE</code> +<a name="index-TREE_005fTYPE-2"></a> +</dt> +<dd><p>This macro returns the type of the entity declared. +</p> +</dd> +<dt><code>EXPR_FILENAME</code> +<a name="index-EXPR_005fFILENAME"></a> +</dt> +<dd><p>This macro returns the name of the file in which the entity was +declared, as a <code>char*</code>. For an entity declared implicitly by the +compiler (like <code>__builtin_memcpy</code>), this will be the string +<code>"<internal>"</code>. +</p> +</dd> +<dt><code>EXPR_LINENO</code> +<a name="index-EXPR_005fLINENO"></a> +</dt> +<dd><p>This macro returns the line number at which the entity was declared, as +an <code>int</code>. +</p> +</dd> +<dt><code>DECL_ARTIFICIAL</code> +<a name="index-DECL_005fARTIFICIAL"></a> +</dt> +<dd><p>This predicate holds if the declaration was implicitly generated by the +compiler. For example, this predicate will hold of an implicitly +declared member function, or of the <code>TYPE_DECL</code> implicitly +generated for a class type. Recall that in C++ code like: +</p><div class="smallexample"> +<pre class="smallexample">struct S {}; +</pre></div> +<p>is roughly equivalent to C code like: +</p><div class="smallexample"> +<pre class="smallexample">struct S {}; +typedef struct S S; +</pre></div> +<p>The implicitly generated <code>typedef</code> declaration is represented by a +<code>TYPE_DECL</code> for which <code>DECL_ARTIFICIAL</code> holds. +</p> +</dd> +</dl> + +<p>The various kinds of declarations include: +</p><dl compact="compact"> +<dt><code>LABEL_DECL</code></dt> +<dd><p>These nodes are used to represent labels in function bodies. For more +information, see <a href="Functions.html#Functions">Functions</a>. These nodes only appear in block +scopes. +</p> +</dd> +<dt><code>CONST_DECL</code></dt> +<dd><p>These nodes are used to represent enumeration constants. The value of +the constant is given by <code>DECL_INITIAL</code> which will be an +<code>INTEGER_CST</code> with the same type as the <code>TREE_TYPE</code> of the +<code>CONST_DECL</code>, i.e., an <code>ENUMERAL_TYPE</code>. +</p> +</dd> +<dt><code>RESULT_DECL</code></dt> +<dd><p>These nodes represent the value returned by a function. When a value is +assigned to a <code>RESULT_DECL</code>, that indicates that the value should +be returned, via bitwise copy, by the function. You can use +<code>DECL_SIZE</code> and <code>DECL_ALIGN</code> on a <code>RESULT_DECL</code>, just as +with a <code>VAR_DECL</code>. +</p> +</dd> +<dt><code>TYPE_DECL</code></dt> +<dd><p>These nodes represent <code>typedef</code> declarations. The <code>TREE_TYPE</code> +is the type declared to have the name given by <code>DECL_NAME</code>. In +some cases, there is no associated name. +</p> +</dd> +<dt><code>VAR_DECL</code></dt> +<dd><p>These nodes represent variables with namespace or block scope, as well +as static data members. The <code>DECL_SIZE</code> and <code>DECL_ALIGN</code> are +analogous to <code>TYPE_SIZE</code> and <code>TYPE_ALIGN</code>. For a declaration, +you should always use the <code>DECL_SIZE</code> and <code>DECL_ALIGN</code> rather +than the <code>TYPE_SIZE</code> and <code>TYPE_ALIGN</code> given by the +<code>TREE_TYPE</code>, since special attributes may have been applied to the +variable to give it a particular size and alignment. You may use the +predicates <code>DECL_THIS_STATIC</code> or <code>DECL_THIS_EXTERN</code> to test +whether the storage class specifiers <code>static</code> or <code>extern</code> were +used to declare a variable. +</p> +<p>If this variable is initialized (but does not require a constructor), +the <code>DECL_INITIAL</code> will be an expression for the initializer. The +initializer should be evaluated, and a bitwise copy into the variable +performed. If the <code>DECL_INITIAL</code> is the <code>error_mark_node</code>, +there is an initializer, but it is given by an explicit statement later +in the code; no bitwise copy is required. +</p> +<p>GCC provides an extension that allows either automatic variables, or +global variables, to be placed in particular registers. This extension +is being used for a particular <code>VAR_DECL</code> if <code>DECL_REGISTER</code> +holds for the <code>VAR_DECL</code>, and if <code>DECL_ASSEMBLER_NAME</code> is not +equal to <code>DECL_NAME</code>. In that case, <code>DECL_ASSEMBLER_NAME</code> is +the name of the register into which the variable will be placed. +</p> +</dd> +<dt><code>PARM_DECL</code></dt> +<dd><p>Used to represent a parameter to a function. Treat these nodes +similarly to <code>VAR_DECL</code> nodes. These nodes only appear in the +<code>DECL_ARGUMENTS</code> for a <code>FUNCTION_DECL</code>. +</p> +<p>The <code>DECL_ARG_TYPE</code> for a <code>PARM_DECL</code> is the type that will +actually be used when a value is passed to this function. It may be a +wider type than the <code>TREE_TYPE</code> of the parameter; for example, the +ordinary type might be <code>short</code> while the <code>DECL_ARG_TYPE</code> is +<code>int</code>. +</p> +</dd> +<dt><code>DEBUG_EXPR_DECL</code></dt> +<dd><p>Used to represent an anonymous debug-information temporary created to +hold an expression as it is optimized away, so that its value can be +referenced in debug bind statements. +</p> +</dd> +<dt><code>FIELD_DECL</code></dt> +<dd><p>These nodes represent non-static data members. The <code>DECL_SIZE</code> and +<code>DECL_ALIGN</code> behave as for <code>VAR_DECL</code> nodes. +The position of the field within the parent record is specified by a +combination of three attributes. <code>DECL_FIELD_OFFSET</code> is the position, +counting in bytes, of the <code>DECL_OFFSET_ALIGN</code>-bit sized word containing +the bit of the field closest to the beginning of the structure. +<code>DECL_FIELD_BIT_OFFSET</code> is the bit offset of the first bit of the field +within this word; this may be nonzero even for fields that are not bit-fields, +since <code>DECL_OFFSET_ALIGN</code> may be greater than the natural alignment +of the field’s type. +</p> +<p>If <code>DECL_C_BIT_FIELD</code> holds, this field is a bit-field. In a bit-field, +<code>DECL_BIT_FIELD_TYPE</code> also contains the type that was originally +specified for it, while DECL_TYPE may be a modified type with lesser precision, +according to the size of the bit field. +</p> +</dd> +<dt><code>NAMESPACE_DECL</code></dt> +<dd><p>Namespaces provide a name hierarchy for other declarations. They +appear in the <code>DECL_CONTEXT</code> of other <code>_DECL</code> nodes. +</p> +</dd> +</dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Internal-structure.html#Internal-structure" accesskey="n" rel="next">Internal structure</a>, Up: <a href="Declarations.html#Declarations" accesskey="u" rel="up">Declarations</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> +</div> + + + +</body> +</html> |