145 lines
6.9 KiB
HTML
145 lines
6.9 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2016 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>GNU Compiler Collection (GCC) Internals: Configure Terms</title>
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<meta name="description" content="GNU Compiler Collection (GCC) Internals: Configure Terms">
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<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Configure Terms">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Source-Tree.html#Source-Tree" rel="up" title="Source Tree">
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<link href="Top-Level.html#Top-Level" rel="next" title="Top Level">
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<link href="Source-Tree.html#Source-Tree" rel="prev" title="Source Tree">
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<style type="text/css">
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-->
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</style>
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</head>
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Configure-Terms"></a>
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<div class="header">
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<p>
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Next: <a href="Top-Level.html#Top-Level" accesskey="n" rel="next">Top Level</a>, Up: <a href="Source-Tree.html#Source-Tree" accesskey="u" rel="up">Source Tree</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>
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</div>
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<hr>
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<a name="Configure-Terms-and-History"></a>
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<h3 class="section">6.1 Configure Terms and History</h3>
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<a name="index-configure-terms"></a>
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<a name="index-canadian"></a>
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<p>The configure and build process has a long and colorful history, and can
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be confusing to anyone who doesn’t know why things are the way they are.
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While there are other documents which describe the configuration process
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in detail, here are a few things that everyone working on GCC should
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know.
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</p>
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<p>There are three system names that the build knows about: the machine you
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are building on (<em>build</em>), the machine that you are building for
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(<em>host</em>), and the machine that GCC will produce code for
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(<em>target</em>). When you configure GCC, you specify these with
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<samp>--build=</samp>, <samp>--host=</samp>, and <samp>--target=</samp>.
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</p>
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<p>Specifying the host without specifying the build should be avoided, as
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<code>configure</code> may (and once did) assume that the host you specify
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is also the build, which may not be true.
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</p>
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<p>If build, host, and target are all the same, this is called a
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<em>native</em>. If build and host are the same but target is different,
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this is called a <em>cross</em>. If build, host, and target are all
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different this is called a <em>canadian</em> (for obscure reasons dealing
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with Canada’s political party and the background of the person working
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on the build at that time). If host and target are the same, but build
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is different, you are using a cross-compiler to build a native for a
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different system. Some people call this a <em>host-x-host</em>,
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<em>crossed native</em>, or <em>cross-built native</em>. If build and target
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are the same, but host is different, you are using a cross compiler to
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build a cross compiler that produces code for the machine you’re
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building on. This is rare, so there is no common way of describing it.
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There is a proposal to call this a <em>crossback</em>.
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</p>
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<p>If build and host are the same, the GCC you are building will also be
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used to build the target libraries (like <code>libstdc++</code>). If build and host
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are different, you must have already built and installed a cross
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compiler that will be used to build the target libraries (if you
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configured with <samp>--target=foo-bar</samp>, this compiler will be called
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<code>foo-bar-gcc</code>).
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</p>
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<p>In the case of target libraries, the machine you’re building for is the
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machine you specified with <samp>--target</samp>. So, build is the machine
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you’re building on (no change there), host is the machine you’re
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building for (the target libraries are built for the target, so host is
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the target you specified), and target doesn’t apply (because you’re not
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building a compiler, you’re building libraries). The configure/make
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process will adjust these variables as needed. It also sets
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<code>$with_cross_host</code> to the original <samp>--host</samp> value in case you
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need it.
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</p>
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<p>The <code>libiberty</code> support library is built up to three times: once
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for the host, once for the target (even if they are the same), and once
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for the build if build and host are different. This allows it to be
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used by all programs which are generated in the course of the build
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process.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Top-Level.html#Top-Level" accesskey="n" rel="next">Top Level</a>, Up: <a href="Source-Tree.html#Source-Tree" accesskey="u" rel="up">Source Tree</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>
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</div>
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</body>
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</html>
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