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92 lines
3.9 KiB
HTML
92 lines
3.9 KiB
HTML
4 years ago
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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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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>GCC (Embed with GNU)</title>
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<meta name="description" content="GCC (Embed with GNU)">
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<meta name="keywords" content="GCC (Embed with GNU)">
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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="leds_002ec.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="index.html#Top" rel="up" title="Top">
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<link href="Overview.html#Overview" rel="next" title="Overview">
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<link href="Board-support.html#Board-support" rel="prev" title="Board support">
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<style type="text/css">
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</head>
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<body lang="en">
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<a name="GCC"></a>
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<div class="header">
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<p>
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Next: <a href="Libraries.html#Libraries" accesskey="n" rel="next">Libraries</a>, Previous: <a href="Libgloss.html#Libgloss" accesskey="p" rel="prev">Libgloss</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="leds_002ec.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>]</p>
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</div>
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<hr>
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<a name="Porting-GCC"></a>
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<h2 class="chapter">2 Porting GCC</h2>
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<p>Porting GCC requires two things, neither of which has anything to do
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with GCC. If GCC already supports a processor type, then all the work in
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porting GCC is really a linker issue. All GCC has to do is produce
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assembler output in the proper syntax. Most of the work is done by the
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linker, which is described elsewhere.
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</p>
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<p>Mostly all GCC does is format the command line for the linker pass. The
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command line for GCC is set in the various config subdirectories of gcc.
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The options of interest to us are <code>CPP_SPEC</code> and
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<code>STARTFILE_SPEC</code>. CPP_SPEC sets the builtin defines for your
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environment. If you support multiple environments with the same
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processor, then OS specific defines will need to be elsewhere.
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</p>
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<p><code>STARTFILE_SPEC</code>
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</p>
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<p>Once you have linker support, GCC will be able to produce a fully linked
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executable image. The only <em>part</em> of GCC that the linker wants is a
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crt0.o, and a memory map. If you plan on running any programs that do
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I/O of any kind, you’ll need to write support for the C library, which
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is described elsewhere.
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</p>
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<table class="menu" border="0" cellspacing="0">
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<tr><td align="left" valign="top">• <a href="Overview.html#Overview" accesskey="1">Overview</a>:</td><td> </td><td align="left" valign="top">An overview as to the compilation passes.
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</td></tr>
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<tr><td align="left" valign="top">• <a href="Options.html#Options" accesskey="2">Options</a>:</td><td> </td><td align="left" valign="top">Useful GCC options for embedded systems.
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</td></tr>
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</table>
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</body>
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</html>
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