109 lines
5.1 KiB
HTML
109 lines
5.1 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<html>
|
|
<!-- Copyright (C) 1988-2016 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 5.2, http://www.gnu.org/software/texinfo/ -->
|
|
<head>
|
|
<title>GNU Compiler Collection (GCC) Internals: Invoking the garbage collector</title>
|
|
|
|
<meta name="description" content="GNU Compiler Collection (GCC) Internals: Invoking the garbage collector">
|
|
<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Invoking the garbage collector">
|
|
<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="Troubleshooting.html#Troubleshooting" rel="next" title="Troubleshooting">
|
|
<link href="Files.html#Files" rel="prev" title="Files">
|
|
<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="Invoking-the-garbage-collector"></a>
|
|
<div class="header">
|
|
<p>
|
|
Next: <a href="Troubleshooting.html#Troubleshooting" accesskey="n" rel="next">Troubleshooting</a>, Previous: <a href="Files.html#Files" accesskey="p" rel="prev">Files</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="How-to-invoke-the-garbage-collector"></a>
|
|
<h3 class="section">22.6 How to invoke the garbage collector</h3>
|
|
<a name="index-garbage-collector_002c-invocation"></a>
|
|
<a name="index-ggc_005fcollect"></a>
|
|
|
|
<p>The GCC garbage collector GGC is only invoked explicitly. In contrast
|
|
with many other garbage collectors, it is not implicitly invoked by
|
|
allocation routines when a lot of memory has been consumed. So the
|
|
only way to have GGC reclaim storage is to call the <code>ggc_collect</code>
|
|
function explicitly. This call is an expensive operation, as it may
|
|
have to scan the entire heap. Beware that local variables (on the GCC
|
|
call stack) are not followed by such an invocation (as many other
|
|
garbage collectors do): you should reference all your data from static
|
|
or external <code>GTY</code>-ed variables, and it is advised to call
|
|
<code>ggc_collect</code> with a shallow call stack. The GGC is an exact mark
|
|
and sweep garbage collector (so it does not scan the call stack for
|
|
pointers). In practice GCC passes don’t often call <code>ggc_collect</code>
|
|
themselves, because it is called by the pass manager between passes.
|
|
</p>
|
|
<p>At the time of the <code>ggc_collect</code> call all pointers in the GC-marked
|
|
structures must be valid or <code>NULL</code>. In practice this means that
|
|
there should not be uninitialized pointer fields in the structures even
|
|
if your code never reads or writes those fields at a particular
|
|
instance. One way to ensure this is to use cleared versions of
|
|
allocators unless all the fields are initialized manually immediately
|
|
after allocation.
|
|
</p>
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|