1 | <sect2><title> </title><para> </para></sect2>
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2 |
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3 | <sect2>
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4 | <title>Re-installation of GCC</title>
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5 |
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6 | <para>The tools required to test GCC and Binutils are installed now (Tcl, Expect
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7 | and DejaGnu). We can continue on rebuilding GCC and Binutils, link them against
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8 | the new Glibc, and test them properly. One thing to note, however, is that these
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9 | test suites are highly dependent on properly functioning pseudo terminals (PTYs)
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10 | which are provided by your host distribution. These days, PTYs are most commonly
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11 | implemented via the <emphasis>devpts</emphasis> file system. You can quickly
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12 | check if your host system is set up correctly in this regard by performing a
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13 | simple test:</para>
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14 |
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15 | <para><screen><userinput>expect -c "spawn ls"</userinput></screen></para>
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16 |
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17 | <para>If you receive the message:</para>
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18 |
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19 | <blockquote><screen>The system has no more ptys. Ask your system administrator to create more.</screen></blockquote>
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20 |
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21 | <para>Your host distribution is not set up for proper PTY operation. In this
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22 | case there is no point in running the test suites for GCC and Binutils until you
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23 | are able to resolve the issue. You can consult the LFS Wiki at
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24 | <ulink url="http://wiki.linuxfromscratch.org/"/> for more information on how to
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25 | get PTYs working.</para>
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26 |
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27 | <note><para>It's worth pointing out that the GCC test suite we run in this
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28 | section is considered not as important as the one we run in Chapter 6.</para></note>
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29 |
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30 | <para>Unpack all three GCC tarballs (-core, -g++, and -testsuite) in one and the
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31 | same working directory. They will all unfold into a single
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32 | <filename>gcc-&gcc-version;/</filename> subdirectory.</para>
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33 |
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34 | <para>First correct one problem and make an essential adjustment:</para>
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35 |
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36 | <para><screen><userinput>patch -Np1 -i ../&gcc-nofixincludes-patch;
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37 | patch -Np1 -i ../&gcc-specs-patch;</userinput></screen></para>
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38 |
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39 | <para>The first patch disables the GCC "fixincludes" script. We mentioned this
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40 | briefly earlier, but a slightly more in-depth explanation of the fixincludes
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41 | process is warranted here. Under normal circumstances, the GCC fixincludes
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42 | script scans your system for header files that need to be fixed. It might find
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43 | that some Glibc header files on your host system need to be fixed, fix them and
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44 | put them in the GCC private include directory. Then, later on in Chapter 6,
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45 | after we've installed the newer Glibc, this private include directory would be
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46 | searched before the system include directory, resulting in GCC finding the
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47 | fixed headers from the host system, which would most likely not match the Glibc
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48 | version actually used for the LFS system.</para>
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49 |
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50 | <para>The last patch changes GCC's default location of the dynamic linker
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51 | (typically <filename>ld-linux.so.2</filename>). It also removes
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52 | <filename class="directory">/usr/include</filename> from GCC's include search
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53 | path. Patching now rather than adjusting the specs file after installation
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54 | ensures that our new dynamic linker gets used during the actual build of GCC.
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55 | That is, all the final (and temporary) binaries created during the build will
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56 | link against the new Glibc.</para>
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57 |
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58 | <important><para>These patches are <emphasis>critical</emphasis> in ensuring a
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59 | successful overall build. Do not forget to apply them.</para></important>
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60 |
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61 | <para>Create a separate build directory again:</para>
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62 |
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63 | <para><screen><userinput>mkdir ../gcc-build
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64 | cd ../gcc-build</userinput></screen></para>
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65 |
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66 | <para>Before starting to build GCC, remember to unset any environment
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67 | variables that override the default optimization flags.</para>
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68 |
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69 | <para>Now prepare GCC to be compiled:</para>
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70 |
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71 | <para><screen><userinput>../gcc-&gcc-version;/configure --prefix=/tools \
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72 | --with-local-prefix=/tools \
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73 | --enable-clocale=gnu --enable-shared \
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74 | --enable-threads=posix --enable-__cxa_atexit \
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75 | --enable-languages=c,c++</userinput></screen></para>
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76 |
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77 | <para>The meaning of the new configure options:</para>
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78 |
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79 | <itemizedlist>
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80 | <listitem><para><userinput>--enable-threads=posix</userinput>: This enables
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81 | C++ exception handling for multi-threaded code.</para></listitem>
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82 |
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83 | <listitem><para><userinput>--enable-__cxa_atexit</userinput>: This option
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84 | allows use of __cxa_atexit, rather than atexit, to register C++ destructors for
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85 | local statics and global objects and is essential for fully standards-compliant
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86 | handling of destructors. It also affects the C++ ABI and therefore results in
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87 | C++ shared libraries and C++ programs that are interoperable with other Linux
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88 | distributions.</para></listitem>
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89 |
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90 | <listitem><para><userinput>--enable-clocale=gnu</userinput>: This option ensures
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91 | the correct locale model is selected for the C++ libraries under all
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92 | circumstances. If the configure script finds the <emphasis>de_DE</emphasis>
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93 | locale installed, it will select the correct model of <emphasis>gnu</emphasis>.
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94 | However, people who don't install the <emphasis>de_DE</emphasis> locale, run the
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95 | risk of building ABI incompatible C++ libraries due to the wrong locale model of
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96 | <emphasis>generic</emphasis> being selected.</para></listitem>
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97 |
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98 | <listitem><para><userinput>--enable-languages=c,c++</userinput>: This option is
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99 | needed to ensure that both C and C++ compilers are built.</para></listitem>
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100 | </itemizedlist>
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101 |
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102 | <para>Compile the package:</para>
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103 |
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104 | <para><screen><userinput>make</userinput></screen></para>
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105 |
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106 | <para>There is no need to use the <userinput>bootstrap</userinput> target now,
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107 | as the compiler we're using to compile this GCC was built from the exact same
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108 | version of the GCC sources we used earlier.</para>
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109 |
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110 | <para>Test the results:</para>
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111 |
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112 | <para><screen><userinput>make -k check</userinput></screen></para>
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113 |
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114 | <para>The <userinput>-k</userinput> flag is used to make the test suite run
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115 | through to completion and not stop at the first failure. The GCC test suite is
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116 | very comprehensive and is almost guaranteed to generate a few failures. To get
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117 | a summary of the test suite results, run this:</para>
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118 |
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119 | <para><screen><userinput>../gcc-&gcc-version;/contrib/test_summary | less</userinput></screen></para>
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120 |
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121 | <para>You can compare your results to those posted to the gcc-testresults
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122 | mailing list for similar configurations to your own. For an example of how
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123 | current GCC-3.3.1 should look on i686-pc-linux-gnu, see
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124 | <ulink url="http://gcc.gnu.org/ml/gcc-testresults/2003-08/msg01612.html"/>.</para>
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125 |
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126 | <para>Note that the results contain:</para>
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127 |
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128 | <screen>* 1 XPASS (unexpected pass) for g++
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129 | * 1 FAIL (unexpected failure) for g++
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130 | * 2 FAIL for gcc
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131 | * 26 XPASS's for libstdc++</screen>
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132 |
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133 | <para>The unexpected pass for g++ is due to the use of
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134 | <userinput>--enable-__cxa_atexit</userinput>. Apparently not all platforms
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135 | supported by GCC have support for "__cxa_atexit" in their C libraries, so this
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136 | test is not always expected to pass.</para>
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137 |
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138 | <para>The 26 unexpected passes for libstdc++ are due to the use of
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139 | <userinput>--enable-clocale=gnu</userinput>, which is the correct choice on
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140 | Glibc-based systems of versions 2.2.5 and above. The underlying locale support
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141 | in the GNU C library is superior to that of the otherwise selected "generic"
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142 | model (which may be applicable if for instance you were using Newlibc, Sun-libc
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143 | or whatever libc). The libstdc++ test suite is apparently expecting the
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144 | "generic" model, hence those tests are not always expected to pass.</para>
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145 |
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146 | <para>Unexpected failures often cannot be avoided. The GCC developers are
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147 | usually aware of them but haven't yet gotten around to fixing them. In short,
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148 | unless your results are vastly different from those at the above URL, it is safe
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149 | to continue on.</para>
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150 |
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151 | <para>And finally install the package:</para>
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152 |
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153 | <para><screen><userinput>make install</userinput></screen></para>
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154 |
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155 | <note><para>At this point it is strongly recommended to repeat the sanity check
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156 | we performed earlier in the chapter. Refer back to
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157 | <xref linkend="ch05-locking-glibc"/> and repeat the check. If the results are
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158 | wrong then most likely, you forgot to apply the above mentioned GCC Specs
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159 | patch.</para></note>
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160 |
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161 | </sect2>
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162 |
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