<!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>Using the GNU Compiler Collection (GCC): What you can and what you cannot do in +load</title>
|
|
<meta name="description" content="Using the GNU Compiler Collection (GCC): What you can and what you cannot do in +load">
|
<meta name="keywords" content="Using the GNU Compiler Collection (GCC): What you can and what you cannot do in +load">
|
<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="Executing-code-before-main.html#Executing-code-before-main" rel="up" title="Executing code before main">
|
<link href="Type-encoding.html#Type-encoding" rel="next" title="Type encoding">
|
<link href="Executing-code-before-main.html#Executing-code-before-main" rel="prev" title="Executing code before main">
|
<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="What-you-can-and-what-you-cannot-do-in-_002bload"></a>
|
<div class="header">
|
<p>
|
Up: <a href="Executing-code-before-main.html#Executing-code-before-main" accesskey="u" rel="up">Executing code before main</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="What-You-Can-and-Cannot-Do-in-_002bload"></a>
|
<h4 class="subsection">8.2.1 What You Can and Cannot Do in <code>+load</code></h4>
|
|
<p><code>+load</code> is to be used only as a last resort. Because it is
|
executed very early, most of the Objective-C runtime machinery will
|
not be ready when <code>+load</code> is executed; hence <code>+load</code> works
|
best for executing C code that is independent on the Objective-C
|
runtime.
|
</p>
|
<p>The <code>+load</code> implementation in the GNU runtime guarantees you the
|
following things:
|
</p>
|
<ul>
|
<li> you can write whatever C code you like;
|
|
</li><li> you can allocate and send messages to objects whose class is implemented
|
in the same file;
|
|
</li><li> the <code>+load</code> implementation of all super classes of a class are
|
executed before the <code>+load</code> of that class is executed;
|
|
</li><li> the <code>+load</code> implementation of a class is executed before the
|
<code>+load</code> implementation of any category.
|
|
</li></ul>
|
|
<p>In particular, the following things, even if they can work in a
|
particular case, are not guaranteed:
|
</p>
|
<ul>
|
<li> allocation of or sending messages to arbitrary objects;
|
|
</li><li> allocation of or sending messages to objects whose classes have a
|
category implemented in the same file;
|
|
</li><li> sending messages to Objective-C constant strings (<code>@"this is a
|
constant string"</code>);
|
|
</li></ul>
|
|
<p>You should make no assumptions about receiving <code>+load</code> in sibling
|
classes when you write <code>+load</code> of a class. The order in which
|
sibling classes receive <code>+load</code> is not guaranteed.
|
</p>
|
<p>The order in which <code>+load</code> and <code>+initialize</code> are called could
|
be problematic if this matters. If you don’t allocate objects inside
|
<code>+load</code>, it is guaranteed that <code>+load</code> is called before
|
<code>+initialize</code>. If you create an object inside <code>+load</code> the
|
<code>+initialize</code> method of object’s class is invoked even if
|
<code>+load</code> was not invoked. Note if you explicitly call <code>+load</code>
|
on a class, <code>+initialize</code> will be called first. To avoid possible
|
problems try to implement only one of these methods.
|
</p>
|
<p>The <code>+load</code> method is also invoked when a bundle is dynamically
|
loaded into your running program. This happens automatically without any
|
intervening operation from you. When you write bundles and you need to
|
write <code>+load</code> you can safely create and send messages to objects whose
|
classes already exist in the running program. The same restrictions as
|
above apply to classes defined in bundle.
|
</p>
|
|
|
<hr>
|
<div class="header">
|
<p>
|
Up: <a href="Executing-code-before-main.html#Executing-code-before-main" accesskey="u" rel="up">Executing code before main</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>
|
