1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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5 | %general-entities;
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6 | ]>
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7 |
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8 | <sect1 id="ch-tools-adjusting">
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9 | <?dbhtml filename="adjusting.html"?>
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10 |
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11 | <title>Adjusting the Toolchain</title>
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12 |
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13 | <para>Now that the temporary C libraries have been installed, all
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14 | tools compiled in the rest of this chapter should be linked against
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15 | these libraries. In order to accomplish this, the linker and the
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16 | compiler's specs file need to be adjusted.</para>
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17 |
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18 | <para>The linker, adjusted at the end of the first pass of Binutils, needs
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19 | to be renamed so that it can be properly found and used. First, backup the
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20 | original linker, then replace it with the adjusted linker. We'll also
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21 | create a link to its counterpart in <filename class="directory">
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22 | /tools/$(gcc -dumpmachine)/bin</filename>:</para>
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23 |
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24 | <screen><userinput>mv -v /tools/bin/{ld,ld-old}
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25 | mv -v /tools/$(gcc -dumpmachine)/bin/{ld,ld-old}
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26 | mv -v /tools/bin/{ld-new,ld}
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27 | ln -sv /tools/bin/ld /tools/$(gcc -dumpmachine)/bin/ld</userinput></screen>
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28 |
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29 | <para>From this point onwards, everything will link only against the
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30 | libraries in <filename class="directory">/tools/lib</filename>.</para>
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31 |
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32 | <para>The next task is to point GCC to the new dynamic linker. This is done by
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33 | dumping GCC's <quote>specs</quote> file to a location where GCC will look for it
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34 | by default. A simple <command>sed</command> substitution then alters the
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35 | dynamic linker that GCC will use.</para>
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36 |
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37 | <para>For the sake of accuracy, it is recommended to use a copy-and-paste
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38 | method when issuing the following command. Be sure to visually inspect the
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39 | specs file and verify that all occurrences of <quote>/lib/ld-linux.so.2</quote>
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40 | have been replaced with <quote>/tools/lib/ld-linux.so.2</quote>:</para>
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41 |
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42 | <important>
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43 | <para>If working on a platform where the name of the dynamic linker is
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44 | something other than <filename class="libraryfile">ld-linux.so.2</filename>,
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45 | replace <quote>ld-linux.so.2</quote> with the name of the platform's
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46 | dynamic linker in the following commands. Refer to <xref
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47 | linkend="ch-tools-toolchaintechnotes" role=","/> if necessary.</para>
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48 | </important>
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49 |
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50 | <!-- Ampersands are needed to allow copy and paste -->
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51 | <screen><userinput>gcc -dumpspecs | sed 's@/lib/ld-linux.so.2@/tools&@g' \
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52 | > `dirname $(gcc -print-libgcc-file-name)`/specs</userinput></screen>
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53 |
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54 | <para>During the build process, GCC runs a script
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55 | (<command>fixincludes</command>) that scans the system for header files
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56 | that may need to be fixed (they might contain syntax errors, for example),
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57 | and installs the fixed versions in a private include directory. There is a
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58 | possibility that, as a result of this process, some header files from the
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59 | host system have found their way into GCC's private include directory. As
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60 | the rest of this chapter only requires the headers from GCC and Glibc,
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61 | which have both been installed at this point, any <quote>fixed</quote>
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62 | headers can safely be removed. This helps to avoid any host headers
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63 | polluting the build environment. Run the following commands to remove the
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64 | header files in GCC's private include directory (you may find it easier to
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65 | copy and paste these commands, rather than typing them by hand, due to
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66 | their length):</para>
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67 |
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68 | <!-- && used to ease copy and pasting -->
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69 | <screen><userinput>GCC_INCLUDEDIR=`dirname $(gcc -print-libgcc-file-name)`/include &&
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70 | find ${GCC_INCLUDEDIR}/* -maxdepth 0 -xtype d -exec rm -rvf '{}' \; &&
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71 | rm -vf `grep -l "DO NOT EDIT THIS FILE" ${GCC_INCLUDEDIR}/*` &&
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72 | unset GCC_INCLUDEDIR</userinput></screen>
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73 |
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74 | <caution>
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75 | <para>At this point, it is imperative to stop and ensure that the basic
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76 | functions (compiling and linking) of the new toolchain are working as
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77 | expected. To perform a sanity check, run the following commands:</para>
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78 |
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79 | <screen><userinput>echo 'main(){}' > dummy.c
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80 | cc dummy.c
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81 | readelf -l a.out | grep ': /tools'</userinput></screen>
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82 |
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83 | <para>If everything is working correctly, there should be no errors,
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84 | and the output of the last command will be of the form:</para>
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85 |
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86 | <screen><computeroutput>[Requesting program interpreter:
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87 | /tools/lib/ld-linux.so.2]</computeroutput></screen>
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88 |
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89 | <para>Note that <filename class="directory">/tools/lib</filename>
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90 | appears as the prefix of the dynamic linker.</para>
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91 |
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92 | <para>If the output is not shown as above or there was no output at all,
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93 | then something is wrong. Investigate and retrace the steps to find out
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94 | where the problem is and correct it. This issue must be resolved before
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95 | continuing on. First, perform the sanity check again, using
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96 | <command>gcc</command> instead of <command>cc</command>. If this works,
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97 | then the <filename class="symlink">/tools/bin/cc</filename> symlink is
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98 | missing. Revisit <xref linkend="ch-tools-gcc-pass1" role=","/> and install
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99 | the symlink. Next, ensure that the <envar>PATH</envar> is correct. This
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100 | can be checked by running <command>echo $PATH</command> and verifying that
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101 | <filename class="directory">/tools/bin</filename> is at the head of the
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102 | list. If the <envar>PATH</envar> is wrong it could mean that you are not
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103 | logged in as user <systemitem class="username">lfs</systemitem> or that
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104 | something went wrong back in <xref linkend="ch-tools-settingenviron"
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105 | role="."/> Another option is that something may have gone wrong with the
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106 | specs file amendment above. In this case, redo the specs file amendment,
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107 | being careful to copy-and-paste the commands.</para>
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108 |
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109 | <para>Once all is well, clean up the test files:</para>
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110 |
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111 | <screen><userinput>rm -v dummy.c a.out</userinput></screen>
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112 |
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113 | </caution>
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114 |
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115 | <note><para>Building Tcl in the next section will serve as an additional check that
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116 | the toolchain has been built properly. If Tcl fails to build, it is an
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117 | indication that something has gone wrong with the Binutils, GCC, or Glibc
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118 | installation, but not with Tcl itself.</para></note>
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119 |
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120 | </sect1>
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