You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
113 lines
4.7 KiB
HTML
113 lines
4.7 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>What you can and what you cannot do in +load - Using the GNU Compiler Collection (GCC)</title>
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<meta name="description" content="Using the GNU Compiler Collection (GCC)">
|
|
<meta name="generator" content="makeinfo 4.13">
|
|
<link title="Top" rel="start" href="index.html#Top">
|
|
<link rel="up" href="Executing-code-before-main.html#Executing-code-before-main" title="Executing code before main">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
Copyright (C) 1988-2015 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.-->
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
|
<style type="text/css"><!--
|
|
pre.display { font-family:inherit }
|
|
pre.format { font-family:inherit }
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
|
pre.smallexample { font-size:smaller }
|
|
pre.smalllisp { font-size:smaller }
|
|
span.sc { font-variant:small-caps }
|
|
span.roman { font-family:serif; font-weight:normal; }
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
|
--></style>
|
|
</head>
|
|
<body>
|
|
<div class="node">
|
|
<a name="What-you-can-and-what-you-cannot-do-in-+load"></a>
|
|
<a name="What-you-can-and-what-you-cannot-do-in-_002bload"></a>
|
|
<p>
|
|
Up: <a rel="up" accesskey="u" href="Executing-code-before-main.html#Executing-code-before-main">Executing code before main</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<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>The <code>+load</code> implementation in the GNU runtime guarantees you the
|
|
following things:
|
|
|
|
<ul>
|
|
<li>you can write whatever C code you like;
|
|
|
|
<li>you can allocate and send messages to objects whose class is implemented
|
|
in the same file;
|
|
|
|
<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>the <code>+load</code> implementation of a class is executed before the
|
|
<code>+load</code> implementation of any category.
|
|
|
|
</ul>
|
|
|
|
<p>In particular, the following things, even if they can work in a
|
|
particular case, are not guaranteed:
|
|
|
|
<ul>
|
|
<li>allocation of or sending messages to arbitrary objects;
|
|
|
|
<li>allocation of or sending messages to objects whose classes have a
|
|
category implemented in the same file;
|
|
|
|
<li>sending messages to Objective-C constant strings (<code>@"this is a
|
|
constant string"</code>);
|
|
|
|
</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>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>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.
|
|
|
|
</body></html>
|
|
|