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247 lines
8.1 KiB
XML
247 lines
8.1 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xml:id="chap-package-notes">
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<title>Package Notes</title>
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<para>This chapter contains information about how to use and maintain
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the Nix expressions for a number of specific packages, such as the
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Linux kernel or X.org.</para>
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<!--============================================================-->
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<section xml:id="sec-linux-kernel">
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<title>Linux kernel</title>
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<para>The Nix expressions to build the Linux kernel are in <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/os-specific/linux/kernel"><filename>pkgs/os-specific/linux/kernel</filename></link>.</para>
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<para>The function that builds the kernel has an argument
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<varname>kernelPatches</varname> which should be a list of
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<literal>{name, patch, extraConfig}</literal> attribute sets, where
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<varname>name</varname> is the name of the patch (which is included in
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the kernel’s <varname>meta.description</varname> attribute),
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<varname>patch</varname> is the patch itself (possibly compressed),
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and <varname>extraConfig</varname> (optional) is a string specifying
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extra options to be concatenated to the kernel configuration file
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(<filename>.config</filename>).</para>
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<para>The kernel derivation exports an attribute
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<varname>features</varname> specifying whether optional functionality
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is or isn’t enabled. This is used in NixOS to implement
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kernel-specific behaviour. For instance, if the kernel has the
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<varname>iwlwifi</varname> feature (i.e. has built-in support for
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Intel wireless chipsets), then NixOS doesn’t have to build the
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external <varname>iwlwifi</varname> package:
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<programlisting>
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modulesTree = [kernel]
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++ pkgs.lib.optional (!kernel.features ? iwlwifi) kernelPackages.iwlwifi
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++ ...;
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</programlisting>
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</para>
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<para>How to add a new (major) version of the Linux kernel to Nixpkgs:
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<orderedlist>
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<listitem>
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<para>Copy the old Nix expression
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(e.g. <filename>linux-2.6.21.nix</filename>) to the new one
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(e.g. <filename>linux-2.6.22.nix</filename>) and update it.</para>
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</listitem>
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<listitem>
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<para>Add the new kernel to <filename>all-packages.nix</filename>
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(e.g., create an attribute
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<varname>kernel_2_6_22</varname>).</para>
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</listitem>
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<listitem>
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<para>Now we’re going to update the kernel configuration. First
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unpack the kernel. Then for each supported platform
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(<literal>i686</literal>, <literal>x86_64</literal>,
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<literal>uml</literal>) do the following:
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<orderedlist>
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<listitem>
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<para>Make an copy from the old
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config (e.g. <filename>config-2.6.21-i686-smp</filename>) to
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the new one
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(e.g. <filename>config-2.6.22-i686-smp</filename>).</para>
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</listitem>
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<listitem>
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<para>Copy the config file for this platform
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(e.g. <filename>config-2.6.22-i686-smp</filename>) to
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<filename>.config</filename> in the kernel source tree.
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</para>
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</listitem>
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<listitem>
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<para>Run <literal>make oldconfig
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ARCH=<replaceable>{i386,x86_64,um}</replaceable></literal>
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and answer all questions. (For the uml configuration, also
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add <literal>SHELL=bash</literal>.) Make sure to keep the
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configuration consistent between platforms (i.e. don’t
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enable some feature on <literal>i686</literal> and disable
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it on <literal>x86_64</literal>).
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</para>
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</listitem>
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<listitem>
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<para>If needed you can also run <literal>make
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menuconfig</literal>:
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<screen>
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$ nix-env -i ncurses
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$ export NIX_CFLAGS_LINK=-lncurses
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$ make menuconfig ARCH=<replaceable>arch</replaceable></screen>
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</para>
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</listitem>
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<listitem>
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<para>Make sure that
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<literal>CONFIG_FB_TILEBLITTING</literal> is <emphasis>not
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set</emphasis> (otherwise <command>fbsplash</command> won't
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work). This option has a tendency to be enabled as a
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side-effect of other options. If it is, investigate why
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(there's probably another option that forces it to be on)
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and fix it.</para>
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</listitem>
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<listitem>
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<para>Copy <filename>.config</filename> over the new config
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file (e.g. <filename>config-2.6.22-i686-smp</filename>).</para>
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</listitem>
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</orderedlist>
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</para>
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</listitem>
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<listitem>
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<para>Test building the kernel: <literal>nix-build -A
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kernel_2_6_22</literal>. If it compiles, ship it! For extra
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credit, try booting NixOS with it.</para>
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</listitem>
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<listitem>
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<para>It may be that the new kernel requires updating the external
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kernel modules and kernel-dependent packages listed in the
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<varname>kernelPackagesFor</varname> function in
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<filename>all-packages.nix</filename> (such as the NVIDIA drivers,
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AUFS, splashutils, etc.). If the updated packages aren’t
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backwards compatible with older kernels, you need to keep the
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older versions and use some conditionals. For example, new
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kernels require splashutils 1.5 while old kernel require 1.3, so
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<varname>kernelPackagesFor</varname> says:
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<programlisting>
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splashutils =
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if kernel.features ? fbSplash then splashutils_13 else
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if kernel.features ? fbConDecor then splashutils_15 else
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null;
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splashutils_13 = ...;
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splashutils_15 = ...;</programlisting>
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</para>
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</listitem>
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</orderedlist>
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</para>
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</section>
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<!--============================================================-->
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<section>
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<title>X.org</title>
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<para>The Nix expressions for the X.org packages reside in
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<filename>pkgs/servers/x11/xorg/default.nix</filename>. This file is
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automatically generated from lists of tarballs in an X.org release.
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As such it should not be modified directly; rather, you should modify
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the lists, the generator script or the file
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<filename>pkgs/servers/x11/xorg/overrides.nix</filename>, in which you
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can override or add to the derivations produced by the
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generator.</para>
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<para>The generator is invoked as follows:
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<screen>
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$ cd pkgs/servers/x11/xorg
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$ cat tarballs-7.5.list extra.list old.list \
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| perl ./generate-expr-from-tarballs.pl
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</screen>
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For each of the tarballs in the <filename>.list</filename> files, the
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script downloads it, unpacks it, and searches its
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<filename>configure.ac</filename> and <filename>*.pc.in</filename>
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files for dependencies. This information is used to generate
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<filename>default.nix</filename>. The generator caches downloaded
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tarballs between runs. Pay close attention to the <literal>NOT FOUND:
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<replaceable>name</replaceable></literal> messages at the end of the
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run, since they may indicate missing dependencies. (Some might be
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optional dependencies, however.)</para>
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<para>A file like <filename>tarballs-7.5.list</filename> contains all
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tarballs in a X.org release. It can be generated like this:
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<screen>
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$ export i="mirror://xorg/X11R7.4/src/everything/"
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$ cat $(PRINT_PATH=1 nix-prefetch-url $i | tail -n 1) \
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| perl -e 'while (<>) { if (/(href|HREF)="([^"]*.bz2)"/) { print "$ENV{'i'}$2\n"; }; }' \
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| sort > tarballs-7.4.list
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</screen>
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<filename>extra.list</filename> contains libraries that aren’t part of
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X.org proper, but are closely related to it, such as
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<literal>libxcb</literal>. <filename>old.list</filename> contains
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some packages that were removed from X.org, but are still needed by
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some people or by other packages (such as
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<varname>imake</varname>).</para>
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<para>If the expression for a package requires derivation attributes
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that the generator cannot figure out automatically (say,
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<varname>patches</varname> or a <varname>postInstall</varname> hook),
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you should modify
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<filename>pkgs/servers/x11/xorg/overrides.nix</filename>.</para>
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</section>
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<!--============================================================-->
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<!--
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<section>
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<title>Gnome</title>
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<para>* Expression is auto-generated</para>
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<para>* How to update</para>
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</section>
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-->
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<!--============================================================-->
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<!--
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<section>
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<title>GCC</title>
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<para>…</para>
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</section>
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-->
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</chapter>
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