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diff --git a/share/doc/gccint/User-GC.html b/share/doc/gccint/User-GC.html new file mode 100644 index 0000000..150641c --- /dev/null +++ b/share/doc/gccint/User-GC.html @@ -0,0 +1,200 @@ +<!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: User GC</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: User GC"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: User GC"> +<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="Type-Information.html#Type-Information" rel="up" title="Type Information"> +<link href="GGC-Roots.html#GGC-Roots" rel="next" title="GGC Roots"> +<link href="Inheritance-and-GTY.html#Inheritance-and-GTY" rel="previous" title="Inheritance and GTY"> +<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="User-GC"></a> +<div class="header"> +<p> +Next: <a href="GGC-Roots.html#GGC-Roots" accesskey="n" rel="next">GGC Roots</a>, Previous: <a href="Inheritance-and-GTY.html#Inheritance-and-GTY" accesskey="p" rel="previous">Inheritance and GTY</a>, Up: <a href="Type-Information.html#Type-Information" accesskey="u" rel="up">Type Information</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="Support-for-user_002dprovided-GC-marking-routines"></a> +<h3 class="section">23.3 Support for user-provided GC marking routines</h3> +<a name="index-user-gc"></a> +<p>The garbage collector supports types for which no automatic marking +code is generated. For these types, the user is required to provide +three functions: one to act as a marker for garbage collection, and +two functions to act as marker and pointer walker for pre-compiled +headers. +</p> +<p>Given a structure <code>struct GTY((user)) my_struct</code>, the following functions +should be defined to mark <code>my_struct</code>: +</p> +<div class="smallexample"> +<pre class="smallexample">void gt_ggc_mx (my_struct *p) +{ + /* This marks field 'fld'. */ + gt_ggc_mx (p->fld); +} + +void gt_pch_nx (my_struct *p) +{ + /* This marks field 'fld'. */ + gt_pch_nx (tp->fld); +} + +void gt_pch_nx (my_struct *p, gt_pointer_operator op, void *cookie) +{ + /* For every field 'fld', call the given pointer operator. */ + op (&(tp->fld), NULL, cookie); +} +</pre></div> + +<p>In general, each marker <code>M</code> should call <code>M</code> for every +pointer field in the structure. Fields that are not allocated in GC +or are not pointers must be ignored. +</p> +<p>For embedded lists (e.g., structures with a <code>next</code> or <code>prev</code> +pointer), the marker must follow the chain and mark every element in +it. +</p> +<p>Note that the rules for the pointer walker <code>gt_pch_nx (my_struct +*, gt_pointer_operator, void *)</code> are slightly different. In this +case, the operation <code>op</code> must be applied to the <em>address</em> of +every pointer field. +</p> +<a name="User_002dprovided-marking-routines-for-template-types"></a> +<h4 class="subsection">23.3.1 User-provided marking routines for template types</h4> +<p>When a template type <code>TP</code> is marked with <code>GTY</code>, all +instances of that type are considered user-provided types. This means +that the individual instances of <code>TP</code> do not need to be marked +with <code>GTY</code>. The user needs to provide template functions to mark +all the fields of the type. +</p> +<p>The following code snippets represent all the functions that need to +be provided. Note that type <code>TP</code> may reference to more than one +type. In these snippets, there is only one type <code>T</code>, but there +could be more. +</p> +<div class="smallexample"> +<pre class="smallexample">template<typename T> +void gt_ggc_mx (TP<T> *tp) +{ + extern void gt_ggc_mx (T&); + + /* This marks field 'fld' of type 'T'. */ + gt_ggc_mx (tp->fld); +} + +template<typename T> +void gt_pch_nx (TP<T> *tp) +{ + extern void gt_pch_nx (T&); + + /* This marks field 'fld' of type 'T'. */ + gt_pch_nx (tp->fld); +} + +template<typename T> +void gt_pch_nx (TP<T *> *tp, gt_pointer_operator op, void *cookie) +{ + /* For every field 'fld' of 'tp' with type 'T *', call the given + pointer operator. */ + op (&(tp->fld), NULL, cookie); +} + +template<typename T> +void gt_pch_nx (TP<T> *tp, gt_pointer_operator, void *cookie) +{ + extern void gt_pch_nx (T *, gt_pointer_operator, void *); + + /* For every field 'fld' of 'tp' with type 'T', call the pointer + walker for all the fields of T. */ + gt_pch_nx (&(tp->fld), op, cookie); +} +</pre></div> + +<p>Support for user-defined types is currently limited. The following +restrictions apply: +</p> +<ol> +<li> Type <code>TP</code> and all the argument types <code>T</code> must be +marked with <code>GTY</code>. + +</li><li> Type <code>TP</code> can only have type names in its argument list. + +</li><li> The pointer walker functions are different for <code>TP<T></code> and +<code>TP<T *></code>. In the case of <code>TP<T></code>, references to +<code>T</code> must be handled by calling <code>gt_pch_nx</code> (which +will, in turn, walk all the pointers inside fields of <code>T</code>). +In the case of <code>TP<T *></code>, references to <code>T *</code> must be +handled by calling the <code>op</code> function on the address of the +pointer (see the code snippets above). +</li></ol> + +<hr> +<div class="header"> +<p> +Next: <a href="GGC-Roots.html#GGC-Roots" accesskey="n" rel="next">GGC Roots</a>, Previous: <a href="Inheritance-and-GTY.html#Inheritance-and-GTY" accesskey="p" rel="previous">Inheritance and GTY</a>, Up: <a href="Type-Information.html#Type-Information" accesskey="u" rel="up">Type Information</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> |