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  1. <?xml version="1.0" encoding="ISO-8859-1"?>
  2. <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  3. "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  4. <!ENTITY % general-entities SYSTEM "../general.ent">
  5. %general-entities;
  6. ]>
  7. <sect1 id="ch-tools-gcc-pass2" role="wrap">
  8. <?dbhtml filename="gcc-pass2.html"?>
  9. <sect1info condition="script">
  10. <productname>gcc</productname>
  11. <productnumber>&gcc-version;</productnumber>
  12. <address>&gcc-url;</address>
  13. </sect1info>
  14. <title>GCC-&gcc-version; - Pass 2</title>
  15. <indexterm zone="ch-tools-gcc-pass2">
  16. <primary sortas="a-GCC">GCC</primary>
  17. <secondary>tools, pass 2</secondary>
  18. </indexterm>
  19. <sect2 role="package">
  20. <title/>
  21. <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
  22. href="../chapter06/gcc.xml"
  23. xpointer="xpointer(/sect1/sect2[1]/para[1])"/>
  24. <segmentedlist>
  25. <segtitle>&buildtime;</segtitle>
  26. <segtitle>&diskspace;</segtitle>
  27. <seglistitem>
  28. <seg>&gcc-ch5p2-sbu;</seg>
  29. <seg>&gcc-ch5p2-du;</seg>
  30. </seglistitem>
  31. </segmentedlist>
  32. </sect2>
  33. <sect2 role="installation">
  34. <title>Installation of GCC</title>
  35. <para>Our first build of GCC has installed a couple of internal system
  36. headers. Normally one of them, <filename>limits.h</filename> will in turn
  37. include the corresponding system <filename>limits.h</filename> header, in
  38. this case, <filename>/tools/include/limits.h</filename>. However, at the
  39. time of the first build of gcc <filename>/tools/include/limits.h</filename>
  40. did not exist, so the internal header that GCC installed is a partial,
  41. self-contained file and does not include the extended features of the
  42. system header. This was adequate for building the temporary libc, but this
  43. build of GCC now requires the full internal header. Create a full version
  44. of the internal header using a command that is identical to what the GCC
  45. build system does in normal circumstances:</para>
  46. <screen><userinput remap="pre">cat gcc/limitx.h gcc/glimits.h gcc/limity.h &gt; \
  47. `dirname $($LFS_TGT-gcc -print-libgcc-file-name)`/include-fixed/limits.h</userinput></screen>
  48. <para>For x86 machines, a bootstrap build of GCC uses the
  49. <option>-fomit-frame-pointer</option> compiler flag. Non-bootstrap builds
  50. omit this flag by default, and the goal should be to produce a compiler
  51. that is exactly the same as if it were bootstrapped. Apply the following
  52. <command>sed</command> command to force the build to use the flag:</para>
  53. <screen><userinput remap="pre">cp -v gcc/Makefile.in{,.tmp}
  54. sed 's/^T_CFLAGS =$/&amp; -fomit-frame-pointer/' gcc/Makefile.in.tmp \
  55. &gt; gcc/Makefile.in</userinput></screen>
  56. <para>Once again, change the location of GCC's default dynamic linker to
  57. use the one installed in <filename
  58. class="directory">/tools</filename>.</para>
  59. <screen><userinput remap="pre">for file in \
  60. $(find gcc/config -name linux64.h -o -name linux.h -o -name sysv4.h)
  61. do
  62. cp -uv $file{,.orig}
  63. sed -e 's@/lib\(64\)\?\(32\)\?/ld@/tools&amp;@g' \
  64. -e 's@/usr@/tools@g' $file.orig &gt; $file
  65. echo '
  66. #undef STANDARD_STARTFILE_PREFIX_1
  67. #undef STANDARD_STARTFILE_PREFIX_2
  68. #define STANDARD_STARTFILE_PREFIX_1 "/tools/lib/"
  69. #define STANDARD_STARTFILE_PREFIX_2 ""' &gt;&gt; $file
  70. touch $file.orig
  71. done</userinput></screen>
  72. <para>As in the first build of GCC it requires the GMP, MPFR and MPC
  73. packages. Unpack the tarballs and move them into the required directory
  74. names:</para>
  75. <screen><userinput remap="pre">tar -Jxf ../mpfr-&mpfr-version;.tar.xz
  76. mv -v mpfr-&mpfr-version; mpfr
  77. tar -Jxf ../gmp-&gmp-version;.tar.xz
  78. mv -v gmp-&gmp-version; gmp
  79. tar -zxf ../mpc-&mpc-version;.tar.gz
  80. mv -v mpc-&mpc-version; mpc</userinput></screen>
  81. <para>Create a separate build directory again:</para>
  82. <screen><userinput remap="pre">mkdir -v ../gcc-build
  83. cd ../gcc-build</userinput></screen>
  84. <para>Before starting to build GCC, remember to unset any environment
  85. variables that override the default optimization flags.</para>
  86. <para>Now prepare GCC for compilation:</para>
  87. <screen><userinput remap="configure">CC=$LFS_TGT-gcc \
  88. AR=$LFS_TGT-ar \
  89. RANLIB=$LFS_TGT-ranlib \
  90. ../gcc-&gcc-version;/configure \
  91. --prefix=/tools \
  92. --with-local-prefix=/tools \
  93. --with-native-system-header-dir=/tools/include \
  94. --enable-clocale=gnu \
  95. --enable-shared \
  96. --enable-threads=posix \
  97. --enable-__cxa_atexit \
  98. --enable-languages=c,c++ \
  99. --disable-libstdcxx-pch \
  100. --disable-multilib \
  101. --disable-bootstrap \
  102. --disable-libgomp \
  103. --with-mpfr-include=$(pwd)/../gcc-&gcc-version;/mpfr/src \
  104. --with-mpfr-lib=$(pwd)/mpfr/src/.libs</userinput></screen>
  105. <variablelist>
  106. <title>The meaning of the new configure options:</title>
  107. <varlistentry>
  108. <term><parameter>--enable-clocale=gnu</parameter></term>
  109. <listitem>
  110. <para>This option ensures the correct locale model is selected
  111. for the C++ libraries under all circumstances. If the configure
  112. script finds the <emphasis>de_DE</emphasis> locale installed,
  113. it will select the correct gnu locale model. However, if the
  114. <emphasis>de_DE</emphasis> locale is not installed, there is the
  115. risk of building Application Binary Interface (ABI)-incompatible
  116. C++ libraries because the incorrect generic locale model may be
  117. selected.</para>
  118. </listitem>
  119. </varlistentry>
  120. <varlistentry>
  121. <term><parameter>--enable-threads=posix</parameter></term>
  122. <listitem>
  123. <para>This enables C++ exception handling for multi-threaded code.</para>
  124. </listitem>
  125. </varlistentry>
  126. <varlistentry>
  127. <term><parameter>--enable-__cxa_atexit</parameter></term>
  128. <listitem>
  129. <para>This option allows use of <function>__cxa_atexit</function>,
  130. rather than <function>atexit</function>, to register C++ destructors
  131. for local statics and global objects. This option is essential for
  132. fully standards-compliant handling of destructors. It also affects
  133. the C++ ABI, and therefore results in C++ shared libraries and C++
  134. programs that are interoperable with other Linux distributions.</para>
  135. </listitem>
  136. </varlistentry>
  137. <varlistentry>
  138. <term><parameter>--enable-languages=c,c++</parameter></term>
  139. <listitem>
  140. <para>This option ensures that both the C and C++ compilers are
  141. built.</para>
  142. </listitem>
  143. </varlistentry>
  144. <varlistentry>
  145. <term><parameter>--disable-libstdcxx-pch</parameter></term>
  146. <listitem>
  147. <para>Do not build the pre-compiled header (PCH) for
  148. <filename class="libraryfile">libstdc++</filename>. It takes up a
  149. lot of space, and we have no use for it.</para>
  150. </listitem>
  151. </varlistentry>
  152. <varlistentry>
  153. <term><parameter>--disable-bootstrap</parameter></term>
  154. <listitem>
  155. <para>For native builds of GCC, the default is to do a "bootstrap"
  156. build. This does not just compile GCC, but compiles it several times.
  157. It uses the programs compiled in a first round to compile itself a
  158. second time, and then again a third time. The second and third
  159. iterations are compared to make sure it can reproduce itself
  160. flawlessly. This also implies that it was compiled correctly.
  161. However, the LFS build method should provide a solid compiler
  162. without the need to bootstrap each time.</para>
  163. </listitem>
  164. </varlistentry>
  165. </variablelist>
  166. <para>Compile the package:</para>
  167. <screen><userinput remap="make">make</userinput></screen>
  168. <para>Install the package:</para>
  169. <screen><userinput remap="install">make install</userinput></screen>
  170. <para>As a finishing touch, create a symlink. Many programs and scripts
  171. run <command>cc</command> instead of <command>gcc</command>, which is
  172. used to keep programs generic and therefore usable on all kinds of UNIX
  173. systems where the GNU C compiler is not always installed. Running
  174. <command>cc</command> leaves the system administrator free to decide
  175. which C compiler to install:</para>
  176. <screen><userinput remap="install">ln -vs gcc /tools/bin/cc</userinput></screen>
  177. <caution>
  178. <para>At this point, it is imperative to stop and ensure that the basic
  179. functions (compiling and linking) of the new toolchain are working as
  180. expected. To perform a sanity check, run the following commands:</para>
  181. <screen><userinput>echo 'main(){}' &gt; dummy.c
  182. cc dummy.c
  183. readelf -l a.out | grep ': /tools'</userinput></screen>
  184. <para>If everything is working correctly, there should be no errors,
  185. and the output of the last command will be of the form:</para>
  186. <screen><computeroutput>[Requesting program interpreter: /tools/lib/ld-linux.so.2]</computeroutput></screen>
  187. <para>Note that <filename class="directory">/tools/lib</filename>, or
  188. <filename class="directory">/tools/lib64</filename> for 64-bit machines
  189. appears as the prefix of the dynamic linker.</para>
  190. <para>If the output is not shown as above or there was no output at all,
  191. then something is wrong. Investigate and retrace the steps to find out
  192. where the problem is and correct it. This issue must be resolved before
  193. continuing on. First, perform the sanity check again, using
  194. <command>gcc</command> instead of <command>cc</command>. If this works,
  195. then the <filename class="symlink">/tools/bin/cc</filename> symlink is
  196. missing. Install the symlink as per above.
  197. Next, ensure that the <envar>PATH</envar> is correct. This
  198. can be checked by running <command>echo $PATH</command> and verifying that
  199. <filename class="directory">/tools/bin</filename> is at the head of the
  200. list. If the <envar>PATH</envar> is wrong it could mean that you are not
  201. logged in as user <systemitem class="username">lfs</systemitem> or that
  202. something went wrong back in <xref linkend="ch-tools-settingenviron"
  203. role="."/></para>
  204. <para>Once all is well, clean up the test files:</para>
  205. <screen><userinput>rm -v dummy.c a.out</userinput></screen>
  206. </caution>
  207. </sect2>
  208. <sect2 role="content">
  209. <title/>
  210. <para>Details on this package are located in
  211. <xref linkend="contents-gcc" role="."/></para>
  212. </sect2>
  213. </sect1>