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authorManuel Canales Esparcia <manuel@linuxfromscratch.org>2006-01-22 13:13:52 +0000
committerManuel Canales Esparcia <manuel@linuxfromscratch.org>2006-01-22 13:13:52 +0000
commitb28fd35a823aac2255671733df034f2327480879 (patch)
treec1d9311a3bcc86bb6fc98feedd8166a598723b5e /chapter05/toolchaintechnotes.xml
parent7b82580d090a238f031978610f2f3df4fd2ebe74 (diff)
Finished chapter 05 indentation.
git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@7292 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
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<?xml version="1.0" encoding="ISO-8859-1"?>
-<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
+<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
+ "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
<!ENTITY % general-entities SYSTEM "../general.ent">
%general-entities;
]>
+
<sect1 id="ch-tools-toolchaintechnotes">
-<title>Toolchain Technical Notes</title>
-<?dbhtml filename="toolchaintechnotes.html"?>
-
-<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 back to at any time during the process.</para>
-
-<para>The overall goal of <xref linkend="chapter-temporary-tools"/> is to
-provide a temporary environment that can be chrooted into and from which can be
-produced a clean, trouble-free build of the target LFS system in <xref
-linkend="chapter-building-system"/>. Along the way, we separate the new system
-from the host system as much as possible, and in doing so, build a
-self-contained and self-hosted toolchain. It should be noted that the build
-process has been designed to minimize the risks for new readers and provide
-maximum educational value at the same time.</para>
-
-<important>
-<para>Before continuing, be aware of the name of the working platform,
-often referred to as the target triplet. Many times, the target
-triplet will probably be <emphasis>i686-pc-linux-gnu</emphasis>. A
-simple way to determine the name of the target 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.</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 will usually be
-<filename class="libraryfile">ld-linux.so.2</filename>. On platforms that are less
-prevalent, the name might be <filename class="libraryfile">ld.so.1</filename>,
-and newer 64 bit platforms might be named something else entirely. The name of
-the platform's dynamic linker can be determined by looking in the
-<filename class="directory">/lib</filename> directory on the host
-system. A sure-fire way to determine the name 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>
-</important>
-
-<para>Some key technical points of how the <xref linkend="chapter-temporary-tools"/> build
-method works:</para>
-
-<itemizedlist>
-<listitem><para>The process is similar in principle to
-cross-compiling, whereby tools installed in the same prefix work in
-cooperation, and thus utilize a little GNU
-<quote>magic</quote></para></listitem>
-
-<listitem><para>Careful manipulation of the standard linker's library
-search path ensures programs are linked only against chosen
-libraries</para></listitem>
-
-<listitem><para>Careful manipulation of <command>gcc</command>'s
-<filename>specs</filename> file tells the compiler which target dynamic
-linker will be used</para></listitem>
-</itemizedlist>
-
-<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">/tools/bin</filename> and <filename
-class="directory">/tools/$TARGET_TRIPLET/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, an <userinput>ld
---verbose | grep SEARCH</userinput> 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,
-<userinput>gcc dummy.c -Wl,--verbose 2&gt;&amp;1 | grep
-succeeded</userinput> 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...
+ <?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
+ back to at any time during the process.</para>
+
+ <para>The overall goal of <xref linkend="chapter-temporary-tools"/> is to
+ provide a temporary environment that can be chrooted into and from which can be
+ produced a clean, trouble-free build of the target LFS system in <xref
+ linkend="chapter-building-system"/>. Along the way, we separate the new system
+ from the host system as much as possible, and in doing so, build a
+ self-contained and self-hosted toolchain. It should be noted that the build
+ process has been designed to minimize the risks for new readers and provide
+ maximum educational value at the same time.</para>
+
+ <important>
+ <para>Before continuing, be aware of the name of the working platform,
+ often referred to as the target triplet. Many times, the target
+ triplet will probably be <emphasis>i686-pc-linux-gnu</emphasis>. A
+ simple way to determine the name of the target 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.</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 will usually be <filename class="libraryfile">ld-linux.so.2</filename>.
+ On platforms that are less prevalent, the name might be <filename
+ class="libraryfile">ld.so.1</filename>, and newer 64 bit platforms might
+ be named something else entirely. The name of the platform's dynamic linker
+ can be determined by looking in the <filename class="directory">/lib</filename>
+ directory on the host system. A sure-fire way to determine the name 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>
+ </important>
+
+ <para>Some key technical points of how the <xref
+ linkend="chapter-temporary-tools"/> build method works:</para>
+
+ <itemizedlist>
+ <listitem>
+ <para>The process is similar in principle to cross-compiling, whereby
+ tools installed in the same prefix work in cooperation, and thus utilize
+ a little GNU <quote>magic</quote></para>
+ </listitem>
+ <listitem>
+ <para>Careful manipulation of the standard linker's library search path
+ ensures programs are linked only against chosen libraries</para>
+ </listitem>
+ <listitem>
+ <para>Careful manipulation of <command>gcc</command>'s
+ <filename>specs</filename> file tells the compiler which target dynamic
+ linker will be used</para>
+ </listitem>
+ </itemizedlist>
+
+ <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">/tools/bin</filename> and <filename
+ class="directory">/tools/$TARGET_TRIPLET/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, an <userinput>ld --verbose | grep SEARCH</userinput>
+ 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,
+ <userinput>gcc dummy.c -Wl,--verbose 2&gt;&amp;1 | grep succeeded</userinput>
+ 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...
/tools/i686-pc-linux-gnu/bin/as
checking what linker to use... /tools/i686-pc-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: <userinput>gcc
--print-prog-name=ld</userinput>.</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, <userinput>gcc -v
-dummy.c</userinput> will show detailed information about the
-preprocessor, compilation, and assembly stages, including
-<command>gcc</command>'s included search paths and their order.</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 <command>gcc</command> found in a
-<envar>PATH</envar> directory.
-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">glibc-build</filename> directory for all important
-details. Note the use of <parameter>CC="gcc -B/tools/bin/"</parameter>
-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>After the Glibc installation, make some adjustments to ensure
-that searching and linking take place only within the <filename
-class="directory">/tools</filename> prefix. Install an adjusted
-<command>ld</command>, which has a hard-wired search path limited to
-<filename class="directory">/tools/lib</filename>. Then amend
-<command>gcc</command>'s specs file to point to the new dynamic linker
-in <filename class="directory">/tools/lib</filename>. This last step
-is vital to the whole process. As mentioned above, a hard-wired path
-to a dynamic linker is embedded into every Executable and Link Format
-(ELF)-shared executable. This can be inspected by running:
-<userinput>readelf -l &lt;name of binary&gt; | grep
-interpreter</userinput>. Amending gcc's specs file
-ensures that every program compiled from here through the end of this
-chapter will use the new dynamic linker in <filename
-class="directory">/tools/lib</filename>.</para>
-
-<para>The need to use the new dynamic linker is also the reason why
-the Specs patch is applied for the second pass of GCC. Failure to do
-so will result in the GCC programs themselves having the name of the
-dynamic linker from the host system's <filename
-class="directory">/lib</filename> directory embedded into them, which
-would defeat the goal of getting away from the host.</para>
-
-<para>During the second pass of Binutils, we are able to utilize the
-<parameter>--with-lib-path</parameter> configure switch to control
-<command>ld</command>'s library search path. From this point onwards,
-the core toolchain is self-contained and self-hosted. The remainder of
-the <xref linkend="chapter-temporary-tools"/> packages all build
-against the new Glibc in <filename
-class="directory">/tools</filename>.</para>
-
-<para>Upon entering the chroot environment in <xref
-linkend="chapter-building-system"/>, the first major package to be
-installed is Glibc, due to its self-sufficient nature mentioned above.
-Once this Glibc is installed into <filename
-class="directory">/usr</filename>, perform a quick changeover of the
-toolchain defaults, then proceed in building the rest of the target
-LFS system.</para>
-
-<!-- Removed as part of the fix for bug 1061 - we no longer build pass1
- packages statically, therefore this explanation isn't required -->
-
-<!--<sect2>
-<title>Notes on Static Linking</title>
-
-<para>Besides their specific task, most programs have to perform many
-common and sometimes trivial operations. These include allocating
-memory, searching directories, reading and writing files, string
-handling, pattern matching, arithmetic, and other tasks. Instead of
-obliging each program to reinvent the wheel, the GNU system provides
-all these basic functions in ready-made libraries. The major library
-on any Linux system is Glibc.</para>
-
-<para>There are two primary ways of linking the functions from a
-library to a program that uses them&mdash;statically or dynamically. When
-a program is linked statically, the code of the used functions is
-included in the executable, resulting in a rather bulky program. When
-a program is dynamically linked, it includes a reference to the
-dynamic linker, the name of the library, and the name of the function,
-resulting in a much smaller executable. A third option is to use the
-programming interface of the dynamic linker (see <filename>dlopen(3)</filename>
-for more information).</para>
-
-<para>Dynamic linking is the default on Linux and has three major
-advantages over static linking. First, only one copy of the executable
-library code is needed on the hard disk, instead of having multiple
-copies of the same code included in several programs, thus saving
-disk space. Second, when several programs use the same library
-function at the same time, only one copy of the function's code is
-required in core, thus saving memory space. Third, when a library
-function gets a bug fixed or is otherwise improved, only the one
-library needs to be recompiled instead of recompiling all programs
-that make use of the improved function.</para>
-
-<para>If dynamic linking has several advantages, why then do we
-statically link the first two packages in this chapter? The reasons
-are threefold&mdash;historical, educational, and technical. The
-historical reason is that earlier versions of LFS statically linked
-every program in this chapter. Educationally, knowing the difference
-between static and dynamic linking is useful. The technical benefit is
-a gained element of independence from the host, meaning that those
-programs can be used independently of the host system. However, it is
-worth noting that an overall successful LFS build can still be
-achieved when the first two packages are built dynamically.</para>
-
-</sect2>-->
+ <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:
+ <userinput>gcc -print-prog-name=ld</userinput>.</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, <userinput>gcc -v dummy.c</userinput> will show
+ detailed information about the preprocessor, compilation, and assembly stages,
+ including <command>gcc</command>'s included search paths and their order.</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
+ <command>gcc</command> found in a <envar>PATH</envar> directory. 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">glibc-build</filename> directory for all important details.
+ Note the use of <parameter>CC="gcc -B/tools/bin/"</parameter> 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>After the Glibc installation, make some adjustments to ensure that
+ searching and linking take place only within the <filename
+ class="directory">/tools</filename> prefix. Install an adjusted
+ <command>ld</command>, which has a hard-wired search path limited to
+ <filename class="directory">/tools/lib</filename>. Then amend
+ <command>gcc</command>'s specs file to point to the new dynamic linker in
+ <filename class="directory">/tools/lib</filename>. This last step is vital
+ to the whole process. As mentioned above, a hard-wired path to a dynamic
+ linker is embedded into every Executable and Link Format (ELF)-shared
+ executable. This can be inspected by running:
+ <userinput>readelf -l &lt;name of binary&gt; | grep interpreter</userinput>.
+ Amending gcc's specs file ensures that every program compiled from here
+ through the end of this chapter will use the new dynamic linker in
+ <filename class="directory">/tools/lib</filename>.</para>
+
+ <para>The need to use the new dynamic linker is also the reason why
+ the Specs patch is applied for the second pass of GCC. Failure to do
+ so will result in the GCC programs themselves having the name of the
+ dynamic linker from the host system's <filename
+ class="directory">/lib</filename> directory embedded into them, which
+ would defeat the goal of getting away from the host.</para>
+
+ <para>During the second pass of Binutils, we are able to utilize the
+ <parameter>--with-lib-path</parameter> configure switch to control
+ <command>ld</command>'s library search path. From this point onwards,
+ the core toolchain is self-contained and self-hosted. The remainder of
+ the <xref linkend="chapter-temporary-tools"/> packages all build against
+ the new Glibc in <filename class="directory">/tools</filename>.</para>
+
+ <para>Upon entering the chroot environment in <xref
+ linkend="chapter-building-system"/>, the first major package to be
+ installed is Glibc, due to its self-sufficient nature mentioned above.
+ Once this Glibc is installed into <filename
+ class="directory">/usr</filename>, perform a quick changeover of the
+ toolchain defaults, then proceed in building the rest of the target
+ LFS system.</para>
+
+ <!-- Removed as part of the fix for bug 1061 - we no longer build pass1
+ packages statically, therefore this explanation isn't required -->
+
+ <!--<sect2>
+ <title>Notes on Static Linking</title>
+
+ <para>Besides their specific task, most programs have to perform many
+ common and sometimes trivial operations. These include allocating
+ memory, searching directories, reading and writing files, string
+ handling, pattern matching, arithmetic, and other tasks. Instead of
+ obliging each program to reinvent the wheel, the GNU system provides
+ all these basic functions in ready-made libraries. The major library
+ on any Linux system is Glibc.</para>
+
+ <para>There are two primary ways of linking the functions from a
+ library to a program that uses them&mdash;statically or dynamically. When
+ a program is linked statically, the code of the used functions is
+ included in the executable, resulting in a rather bulky program. When
+ a program is dynamically linked, it includes a reference to the
+ dynamic linker, the name of the library, and the name of the function,
+ resulting in a much smaller executable. A third option is to use the
+ programming interface of the dynamic linker (see <filename>dlopen(3)</filename>
+ for more information).</para>
+
+ <para>Dynamic linking is the default on Linux and has three major
+ advantages over static linking. First, only one copy of the executable
+ library code is needed on the hard disk, instead of having multiple
+ copies of the same code included in several programs, thus saving
+ disk space. Second, when several programs use the same library
+ function at the same time, only one copy of the function's code is
+ required in core, thus saving memory space. Third, when a library
+ function gets a bug fixed or is otherwise improved, only the one
+ library needs to be recompiled instead of recompiling all programs
+ that make use of the improved function.</para>
+
+ <para>If dynamic linking has several advantages, why then do we
+ statically link the first two packages in this chapter? The reasons
+ are threefold&mdash;historical, educational, and technical. The
+ historical reason is that earlier versions of LFS statically linked
+ every program in this chapter. Educationally, knowing the difference
+ between static and dynamic linking is useful. The technical benefit is
+ a gained element of independence from the host, meaning that those
+ programs can be used independently of the host system. However, it is
+ worth noting that an overall successful LFS build can still be
+ achieved when the first two packages are built dynamically.</para>
+
+ </sect2>-->
</sect1>
-