Slightly change the layout in part III, so that the preliminary material

appear separated. Minor rewrites for accounting for the new layout

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-<?xml version="1.0" encoding="ISO-8859-1"?>
-<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
-  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
-  <!ENTITY % general-entities SYSTEM "../general.ent">
-  %general-entities;
-]>
-
-<sect1 id="ch-tools-toolchaintechnotes">
-  <?dbhtml filename="toolchaintechnotes.html"?>
-
-  <title>Toolchain Technical Notes</title>
-
-  <para>This section explains some of the rationale and technical details
-  behind the overall build method. It is not essential to immediately
-  understand everything in this section. Most of this information will be
-  clearer after performing an actual build. This section can be referred
-  to at any time during the process.</para>
-
-  <para>The overall goal of this chapter and <xref
-  linkend="chapter-temporary-tools"/> is to produce a temporary area that
-  contains a known-good set of tools that can be isolated from the host system.
-  By using <command>chroot</command>, the commands in the remaining chapters
-  will be contained within that environment, ensuring a clean, trouble-free
-  build of the target LFS system. The build process has been designed to
-  minimize the risks for new readers and to provide the most educational value
-  at the same time.</para>
-
-  <para>The build process is based on the process of
-  <emphasis>cross-compilation</emphasis>. Cross-compilation is normally used
-  for building a compiler and its toolchain for a machine different from
-  the one that is used for the build. This is not strictly needed for LFS,
-  since the machine where the new system will run is the same as the one
-  used for the build. But cross-compilation has the great advantage that
-  anything that is cross-compiled cannot depend on the host environment.</para>
-
-  <sect2 id="cross-compile" xreflabel="About Cross-Compilation">
-
-    <title>About Cross-Compilation</title>
-
-    <para>Cross-compilation involves some concepts that deserve a section on
-    their own. Although this section may be omitted in a first reading, it
-    is strongly suggested to come back to it later in order to get a full
-    grasp of the build process.</para>
-
-    <para>Let us first define some terms used in this context:</para>
-
-    <variablelist>
-      <varlistentry><term>build</term><listitem>
-        <para>is the machine where we build programs. Note that this machine
-        is referred to as the <quote>host</quote> in other
-        sections.</para></listitem>
-      </varlistentry>
-
-      <varlistentry><term>host</term><listitem>
-        <para>is the machine/system where the built programs will run. Note
-        that this use of <quote>host</quote> is not the same as in other
-        sections.</para></listitem>
-      </varlistentry>
-
-      <varlistentry><term>target</term><listitem>
-        <para>is only used for compilers. It is the machine the compiler
-        produces code for. It may be different from both build and
-        host.</para></listitem>
-      </varlistentry>
-
-    </variablelist>
-
-    <para>As an example, let us imagine the following scenario: we may have a
-    compiler on a slow machine only, let's call the machine A, and the compiler
-    ccA. We may have also a fast machine (B), but with no compiler, and we may
-    want to produce code for a another slow machine (C). Then, to build a
-    compiler for machine C, we would have three stages:</para>
-
-    <informaltable align="center">
-      <tgroup cols="5">
-        <colspec colnum="1" align="center"/>
-        <colspec colnum="2" align="center"/>
-        <colspec colnum="3" align="center"/>
-        <colspec colnum="4" align="center"/>
-        <colspec colnum="5" align="left"/>
-        <thead>
-          <row><entry>Stage</entry><entry>Build</entry><entry>Host</entry>
-               <entry>Target</entry><entry>Action</entry></row>
-        </thead>
-        <tbody>
-          <row>
-            <entry>1</entry><entry>A</entry><entry>A</entry><entry>B</entry>
-            <entry>build cross-compiler cc1 using ccA on machine A</entry>
-          </row>
-          <row>
-            <entry>2</entry><entry>A</entry><entry>B</entry><entry>B</entry>
-            <entry>build cross-compiler cc2 using cc1 on machine A</entry>
-          </row>
-          <row>
-            <entry>3</entry><entry>B</entry><entry>C</entry><entry>C</entry>
-            <entry>build compiler ccC using cc2 on machine B</entry>
-          </row>
-        </tbody>
-      </tgroup>
-    </informaltable>
-
-    <para>Then, all the other programs needed by machine C can be compiled
-    using cc2 on the fast machine B. Note that unless B can run programs
-    produced for C, there is no way to test the built programs until machine
-    C itself is running. For example, for testing ccC, we may want to add a
-    fourth stage:</para>
-
-    <informaltable align="center">
-      <tgroup cols="5">
-        <colspec colnum="1" align="center"/>
-        <colspec colnum="2" align="center"/>
-        <colspec colnum="3" align="center"/>
-        <colspec colnum="4" align="center"/>
-        <colspec colnum="5" align="left"/>
-        <thead>
-          <row><entry>Stage</entry><entry>Build</entry><entry>Host</entry>
-               <entry>Target</entry><entry>Action</entry></row>
-        </thead>
-        <tbody>
-          <row>
-            <entry>4</entry><entry>C</entry><entry>C</entry><entry>C</entry>
-            <entry>rebuild  and test ccC using itself on machine C</entry>
-          </row>
-        </tbody>
-      </tgroup>
-    </informaltable>
-
-    <para>In the example above, only cc1 and cc2 are cross-compilers, that is,
-    they produce code for a machine different from the one they are run on.
-    The other compilers ccA and ccC produce code for the machine they are run
-    on. Such compilers are called <emphasis>native</emphasis> compilers.</para>
-
-  </sect2>
-
-  <sect2 id="lfs-cross">
-    <title>Implementation of Cross-Compilation for LFS</title>
-
-    <note>
-      <para>Almost all the build systems use names of the form
-      cpu-vendor-kernel-os referred to as the machine triplet. An astute
-      reader may wonder why a <quote>triplet</quote> refers to a four component
-      name. The reason is history: initially, three component names were enough
-      to designate unambiguously a machine, but with new machines and systems
-      appearing, that proved insufficient. The word <quote>triplet</quote>
-      remained. A simple way to determine your machine triplet is to run
-      the <command>config.guess</command>
-      script that comes with the source for many packages. Unpack the binutils
-      sources and run the script: <userinput>./config.guess</userinput> and note
-      the output. For example, for a 32-bit Intel processor the
-      output will be <emphasis>i686-pc-linux-gnu</emphasis>. On a 64-bit
-      system it will be <emphasis>x86_64-pc-linux-gnu</emphasis>.</para>
-
-      <para>Also be aware of the name of the platform's dynamic linker, often
-      referred to as the dynamic loader (not to be confused with the standard
-      linker <command>ld</command> that is part of binutils). The dynamic linker
-      provided by Glibc finds and loads the shared libraries needed by a
-      program, prepares the program to run, and then runs it. The name of the
-      dynamic linker for a 32-bit Intel machine will be <filename
-      class="libraryfile">ld-linux.so.2</filename> (<filename
-      class="libraryfile">ld-linux-x86-64.so.2</filename> for 64-bit systems). A
-      sure-fire way to determine the name of the dynamic linker is to inspect a
-      random binary from the host system by running: <userinput>readelf -l
-      &lt;name of binary&gt; | grep interpreter</userinput> and noting the
-      output. The authoritative reference covering all platforms is in the
-      <filename>shlib-versions</filename> file in the root of the Glibc source
-      tree.</para>
-    </note>
-
-    <para>In order to fake a cross compilation, the name of the host triplet
-    is slightly adjusted by changing the &quot;vendor&quot; field in the
-    <envar>LFS_TGT</envar> variable. We also use the
-    <parameter>--with-sysroot</parameter> option when building the cross linker and
-    cross compiler to tell them where to find the needed host files. This
-    ensures that none of the other programs built in <xref
-    linkend="chapter-temporary-tools"/> can link to libraries on the build
-    machine. Only two stages are mandatory, and one more for tests:</para>
-
-    <informaltable align="center">
-      <tgroup cols="5">
-        <colspec colnum="1" align="center"/>
-        <colspec colnum="2" align="center"/>
-        <colspec colnum="3" align="center"/>
-        <colspec colnum="4" align="center"/>
-        <colspec colnum="5" align="left"/>
-        <thead>
-          <row><entry>Stage</entry><entry>Build</entry><entry>Host</entry>
-               <entry>Target</entry><entry>Action</entry></row>
-        </thead>
-        <tbody>
-          <row>
-            <entry>1</entry><entry>pc</entry><entry>pc</entry><entry>lfs</entry>
-            <entry>build cross-compiler cc1 using cc-pc on pc</entry>
-          </row>
-          <row>
-            <entry>2</entry><entry>pc</entry><entry>lfs</entry><entry>lfs</entry>
-            <entry>build compiler cc-lfs using cc1 on pc</entry>
-          </row>
-          <row>
-            <entry>3</entry><entry>lfs</entry><entry>lfs</entry><entry>lfs</entry>
-            <entry>rebuild and test cc-lfs using itself on lfs</entry>
-          </row>
-        </tbody>
-      </tgroup>
-    </informaltable>
-
-    <para>In the above table, <quote>on pc</quote> means the commands are run
-    on a machine using the already installed distribution. <quote>On
-    lfs</quote> means the commands are run in a chrooted environment.</para>
-
-    <para>Now, there is more about cross-compiling: the C language is not
-    just a compiler, but also defines a standard library. In this book, the
-    GNU C library, named glibc, is used. This library must
-    be compiled for the lfs machine, that is, using the cross compiler cc1. 
-    But the compiler itself uses an internal library implementing complex
-    instructions not available in the assembler instruction set. This
-    internal library is named libgcc, and must be linked to the glibc
-    library to be fully functional! Furthermore, the standard library for
-    C++ (libstdc++) also needs being linked to glibc. The solution
-    to this chicken and egg problem is to first build a degraded cc1 based libgcc,
-    lacking some fuctionalities such as threads and exception handling, then
-    build glibc using this degraded compiler (glibc itself is not
-    degraded), then build libstdc++. But this last library will lack the
-    same functionalities as libgcc.</para>
-
-    <para>This is not the end of the story: the conclusion of the preceding
-    paragraph is that cc1 is unable to build a fully functional libstdc++, but
-    this is the only compiler available for building the C/C++ libraries
-    during stage 2! Of course, the compiler built during stage 2, cc-lfs,
-    would be able to build those libraries, but (1) the build system of
-    GCC does not know that it is usable on pc, and (2) using it on pc
-    would be at risk of linking to the pc libraries, since cc-lfs is a native
-    compiler. So we have to build libstdc++ later, in chroot.</para>
-
-  </sect2>
-
-  <sect2 id="other-details">
-
-    <title>Other procedural details</title>
-
-    <para>The cross-compiler will be installed in a separate <filename
-    class="directory">$LFS/tools</filename> directory, since it will not
-    be part of the final system.</para>
-
-    <para>Binutils is installed first because the <command>configure</command>
-    runs of both GCC and Glibc perform various feature tests on the assembler
-    and linker to determine which software features to enable or disable. This
-    is more important than one might first realize. An incorrectly configured
-    GCC or Glibc can result in a subtly broken toolchain, where the impact of
-    such breakage might not show up until near the end of the build of an
-    entire distribution. A test suite failure will usually highlight this error
-    before too much additional work is performed.</para>
-
-    <para>Binutils installs its assembler and linker in two locations,
-    <filename class="directory">$LFS/tools/bin</filename> and <filename
-    class="directory">$LFS/tools/$LFS_TGT/bin</filename>. The tools in one
-    location are hard linked to the other. An important facet of the linker is
-    its library search order. Detailed information can be obtained from
-    <command>ld</command> by passing it the <parameter>--verbose</parameter>
-    flag. For example, <command>$LFS_TGT-ld --verbose | grep SEARCH</command>
-    will illustrate the current search paths and their order. It shows which
-    files are linked by <command>ld</command> by compiling a dummy program and
-    passing the <parameter>--verbose</parameter> switch to the linker. For
-    example,
-    <command>$LFS_TGT-gcc dummy.c -Wl,--verbose 2&gt;&amp;1 | grep succeeded</command>
-    will show all the files successfully opened during the linking.</para>
-
-    <para>The next package installed is GCC. An example of what can be
-    seen during its run of <command>configure</command> is:</para>
-
-<screen><computeroutput>checking what assembler to use... /mnt/lfs/tools/i686-lfs-linux-gnu/bin/as
-checking what linker to use... /mnt/lfs/tools/i686-lfs-linux-gnu/bin/ld</computeroutput></screen>
-
-    <para>This is important for the reasons mentioned above. It also
-    demonstrates that GCC's configure script does not search the PATH
-    directories to find which tools to use. However, during the actual
-    operation of <command>gcc</command> itself, the same search paths are not
-    necessarily used. To find out which standard linker <command>gcc</command>
-    will use, run: <command>$LFS_TGT-gcc -print-prog-name=ld</command>.</para>
-
-    <para>Detailed information can be obtained from <command>gcc</command> by
-    passing it the <parameter>-v</parameter> command line option while compiling
-    a dummy program. For example, <command>gcc -v dummy.c</command> will show
-    detailed information about the preprocessor, compilation, and assembly
-    stages, including <command>gcc</command>'s included search paths and their
-    order.</para>
-
-    <para>Next installed are sanitized Linux API headers. These allow the
-    standard C library (Glibc) to interface with features that the Linux
-    kernel will provide.</para>
-
-    <para>The next package installed is Glibc. The most important
-    considerations for building Glibc are the compiler, binary tools, and
-    kernel headers. The compiler is generally not an issue since Glibc will
-    always use the compiler relating to the <parameter>--host</parameter>
-    parameter passed to its configure script; e.g. in our case, the compiler
-    will be <command>$LFS_TGT-gcc</command>. The binary tools and kernel
-    headers can be a bit more complicated. Therefore, take no risks and use
-    the available configure switches to enforce the correct selections. After
-    the run of <command>configure</command>, check the contents of the
-    <filename>config.make</filename> file in the <filename
-    class="directory">build</filename> directory for all important details.
-    Note the use of <parameter>CC="$LFS_TGT-gcc"</parameter> (with
-    <envar>$LFS_TGT</envar> expanded) to control which binary tools are used
-    and the use of the <parameter>-nostdinc</parameter> and
-    <parameter>-isystem</parameter> flags to control the compiler's include
-    search path. These items highlight an important aspect of the Glibc
-    package&mdash;it is very self-sufficient in terms of its build machinery
-    and generally does not rely on toolchain defaults.</para>
-
-    <para>As said above, the standard C++ library is compiled next, followed in
-    Chapter 6 by all the programs that need themselves to be built. The install
-    step of libstdc++ uses the <envar>DESTDIR</envar> variable to have the
-    programs land into the LFS filesystem.</para>
-
-    <para>In Chapter 7 the native lfs compiler is built. First binutils-pass2,
-    with the same <envar>DESTDIR</envar> install as the other programs is
-    built, and then the second pass of GCC is constructed, omitting libstdc++
-    and other non-important libraries.  Due to some weird logic in GCC's
-    configure script, <envar>CC_FOR_TARGET</envar> ends up as
-    <command>cc</command> when the host is the same as the target, but is
-    different from the build system. This is why
-    <parameter>CC_FOR_TARGET=$LFS_TGT-gcc</parameter> is put explicitely into
-    the configure options.</para>
-
-    <para>Upon entering the chroot environment in <xref
-    linkend="chapter-chroot-temporary-tools"/>, the first task is to install
-    libstdc++. Then temporary installations of programs needed for the proper
-    operation of the toolchain are performed. Programs needed for testing
-    other programs are also built. From this point onwards, the
-    core toolchain is self-contained and self-hosted.  In 
-    <xref linkend="chapter-building-system"/>, final versions of all the
-    packages needed for a fully functional system are built, tested and
-    installed.</para>
-
-  </sect2>
-
-</sect1>