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diff --git a/share/doc/gccint/Inheritance-and-GTY.html b/share/doc/gccint/Inheritance-and-GTY.html new file mode 100644 index 0000000..7a628a3 --- /dev/null +++ b/share/doc/gccint/Inheritance-and-GTY.html @@ -0,0 +1,139 @@ +<!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: Inheritance and GTY</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Inheritance and GTY"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Inheritance and GTY"> +<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="User-GC.html#User-GC" rel="next" title="User GC"> +<link href="GTY-Options.html#GTY-Options" rel="previous" title="GTY Options"> +<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="Inheritance-and-GTY"></a> +<div class="header"> +<p> +Next: <a href="User-GC.html#User-GC" accesskey="n" rel="next">User GC</a>, Previous: <a href="GTY-Options.html#GTY-Options" accesskey="p" rel="previous">GTY Options</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-inheritance"></a> +<h3 class="section">23.2 Support for inheritance</h3> +<p>gengtype has some support for simple class hierarchies. You can use +this to have gengtype autogenerate marking routines, provided: +</p> +<ul> +<li> There must be a concrete base class, with a discriminator expression +that can be used to identify which subclass an instance is. +</li><li> Only single inheritance is used. +</li><li> None of the classes within the hierarchy are templates. +</li></ul> + +<p>If your class hierarchy does not fit in this pattern, you must use +<a href="User-GC.html#User-GC">User GC</a> instead. +</p> +<p>The base class and its discriminator must be identified using the “desc” +option. Each concrete subclass must use the “tag” option to identify +which value of the discriminator it corresponds to. +</p> +<p>Every class in the hierarchy must have a <code>GTY(())</code> marker, as +gengtype will only attempt to parse classes that have such a marker +<a name="DOCF8" href="#FOOT8"><sup>8</sup></a>. +</p> +<div class="smallexample"> +<pre class="smallexample">class GTY((desc("%h.kind"), tag("0"))) example_base +{ +public: + int kind; + tree a; +}; + +class GTY((tag("1"))) some_subclass : public example_base +{ +public: + tree b; +}; + +class GTY((tag("2"))) some_other_subclass : public example_base +{ +public: + tree c; +}; +</pre></div> + +<p>The generated marking routines for the above will contain a “switch” +on “kind”, visiting all appropriate fields. For example, if kind is +2, it will cast to “some_other_subclass” and visit fields a, b, and c. +</p> +<div class="footnote"> +<hr> +<h4 class="footnotes-heading">Footnotes</h4> + +<h3><a name="FOOT8" href="#DOCF8">(8)</a></h3> +<p>Classes lacking such a marker will not be identified as being +part of the hierarchy, and so the marking routines will not handle them, +leading to a assertion failure within the marking routines due to an +unknown tag value (assuming that assertions are enabled).</p> +</div> + + + +</body> +</html> |