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111 lines
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111 lines
5.4 KiB
HTML
4 years ago
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<html lang="en">
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<title>Configure Terms - GNU Compiler Collection (GCC) Internals</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="GNU Compiler Collection (GCC) Internals">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Source-Tree.html#Source-Tree" title="Source Tree">
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<link rel="next" href="Top-Level.html#Top-Level" title="Top Level">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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Copyright (C) 1988-2015 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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</head>
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<body>
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<div class="node">
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<a name="Configure-Terms"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Top-Level.html#Top-Level">Top Level</a>,
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Up: <a rel="up" accesskey="u" href="Source-Tree.html#Source-Tree">Source Tree</a>
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<hr>
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</div>
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<h3 class="section">6.1 Configure Terms and History</h3>
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<p><a name="index-configure-terms-1662"></a><a name="index-canadian-1663"></a>
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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>There are three system names that the build knows about: the machine you
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are building on (<dfn>build</dfn>), the machine that you are building for
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(<dfn>host</dfn>), and the machine that GCC will produce code for
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(<dfn>target</dfn>). When you configure GCC, you specify these with
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<samp><span class="option">--build=</span></samp>, <samp><span class="option">--host=</span></samp>, and <samp><span class="option">--target=</span></samp>.
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<p>Specifying the host without specifying the build should be avoided, as
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<samp><span class="command">configure</span></samp> 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>If build, host, and target are all the same, this is called a
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<dfn>native</dfn>. If build and host are the same but target is different,
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this is called a <dfn>cross</dfn>. If build, host, and target are all
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different this is called a <dfn>canadian</dfn> (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 <dfn>host-x-host</dfn>,
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<dfn>crossed native</dfn>, or <dfn>cross-built native</dfn>. 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 <dfn>crossback</dfn>.
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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><span class="option">--target=foo-bar</span></samp>, this compiler will be called
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<samp><span class="command">foo-bar-gcc</span></samp>).
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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><span class="option">--target</span></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><span class="option">--host</span></samp> value in case you
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need it.
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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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</body></html>
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