1 | <?xml version="1.0" encoding="UTF-8"?>
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2 | <!DOCTYPE chapter 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="la-files" xreflabel="Libtool archive (.la) files">
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9 | <?dbhtml filename="la-files.html"?>
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10 |
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11 |
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12 | <title>About Libtool Archive (.la) files</title>
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13 |
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14 | <!-- section g : 'Others' in longindex.html -->
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15 | <indexterm zone="la-files">
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16 | <primary sortas="g-la-files">Library archive (.la) files</primary>
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17 | </indexterm>
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18 |
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19 | <sect2 role="package">
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20 | <title>Files with a .la extension</title>
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21 |
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22 | <para>
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23 |
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24 | In LFS and BLFS, many packages use an internally shipped libtool copy to
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25 | build on a variety of Unix platforms. This includes platforms such as
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26 | AIX, Solaris, IRIX, HP-UX, and Cygwin as well as Linux. The origins of
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27 | this tool are quite dated. It was intended to manage libraries on
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28 | systems with less advanced capabilities than a modern Linux system.
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29 |
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30 | </para>
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31 |
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32 | <para>
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33 |
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34 | On a Linux system, libtool specific files are generally unneeded.
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35 | Normally libraries are specified in the build process during the link
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36 | phase. Since a linux system uses the <ulink
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37 | url="https://en.wikipedia.org/wiki/Executable_and_Linkable_Format">
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38 | Executable and Linkable Format (ELF)</ulink> for executables and
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39 | dynamic libraries, information needed to complete the task is embedded
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40 | in the files. Both the linker and the program loader can query the
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41 | appropriate files and properly link or execute the program.
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42 |
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43 | </para>
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44 |
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45 | <para>
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46 | Static libraries are rarely used in LFS and BLFS. And, nowadays most
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47 | packages store the information needed for linking against a static
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48 | library into a .pc file, instead of relying on libtool.
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49 | A <command>pkg-config --static --libs</command> command will output
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50 | the sufficient flags for the linker to link against a static library
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51 | without any libtool magic.
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52 | </para>
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53 |
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54 | <para>
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55 | The problem is that libtool usually creates one or more text files for
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56 | package libraries called libtool archives. These small files have a
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57 | ".la" extension and contain information that is similar to that embedded
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58 | in the libraries or pkg-config files. When building a package that
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59 | uses libtool, the process automatically looks for these files.
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60 | Sometimes a .la file can contains the name or path of a static library
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61 | used during build but not installed, then the build process will break
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62 | because the .la file refers to something nonexistent on the system.
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63 | Similarly, if a package is updated and no longer uses the .la file,
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64 | then the build process can break with the old .la files.
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65 | </para>
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66 |
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67 | <para>
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68 |
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69 | The solution is to remove the .la files. However there is a catch.
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70 | Some packages, such as <xref linkend='imagemagick'/>, use a libtool
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71 | function, lt_dlopen, to load libraries as needed during execution and
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72 | resolve their dependencies at run time. In this case, the .la files
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73 | should remain.
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74 |
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75 | </para>
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76 |
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77 | <para>
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78 |
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79 | The script below, removes all unneeded .la files and saves them in a
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80 | directory, /var/local/la-files by default, not in the normal library
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81 | path. It also searches all pkg-config files (.pc) for embedded
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82 | references to .la files and fixes them to be conventional library
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83 | references needed when an application or library is built. It
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84 | can be run as needed to clean up the directories that may be causing
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85 | problems.
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86 |
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87 | </para>
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88 |
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89 | <screen role="root"><userinput>cat > /usr/sbin/remove-la-files.sh << "EOF"
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90 | <literal>#!/bin/bash
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91 |
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92 | # /usr/sbin/remove-la-files.sh
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93 | # Written for Beyond Linux From Scratch
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94 | # by Bruce Dubbs <bdubbs@&lfs-domainname;>
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95 |
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96 | # Make sure we are running with root privs
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97 | if test "${EUID}" -ne 0; then
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98 | echo "Error: $(basename ${0}) must be run as the root user! Exiting..."
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99 | exit 1
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100 | fi
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101 |
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102 | # Make sure PKG_CONFIG_PATH is set if discarded by sudo
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103 | source /etc/profile
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104 |
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105 | OLD_LA_DIR=/var/local/la-files
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106 |
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107 | mkdir -p $OLD_LA_DIR
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108 |
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109 | # Only search directories in /opt, but not symlinks to directories
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110 | OPTDIRS=$(find /opt -mindepth 1 -maxdepth 1 -type d)
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111 |
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112 | # Move any found .la files to a directory out of the way
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113 | find /usr/lib $OPTDIRS -name "*.la" ! -path "/usr/lib/ImageMagick*" \
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114 | -exec mv -fv {} $OLD_LA_DIR \;
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115 | ###############
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116 |
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117 | # Fix any .pc files that may have .la references
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118 |
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119 | STD_PC_PATH='/usr/lib/pkgconfig
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120 | /usr/share/pkgconfig
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121 | /usr/local/lib/pkgconfig
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122 | /usr/local/share/pkgconfig'
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123 |
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124 | # For each directory that can have .pc files
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125 | for d in $(echo $PKG_CONFIG_PATH | tr : ' ') $STD_PC_PATH; do
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126 |
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127 | # For each pc file
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128 | for pc in $d/*.pc ; do
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129 | if [ $pc == "$d/*.pc" ]; then continue; fi
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130 |
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131 | # Check each word in a line with a .la reference
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132 | for word in $(grep '\.la' $pc); do
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133 | if $(echo $word | grep -q '.la$' ); then
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134 | mkdir -p $d/la-backup
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135 | cp -fv $pc $d/la-backup
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136 |
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137 | basename=$(basename $word )
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138 | libref=$(echo $basename|sed -e 's/^lib/-l/' -e 's/\.la$//')
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139 |
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140 | # Fix the .pc file
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141 | sed -i "s:$word:$libref:" $pc
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142 | fi
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143 | done
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144 | done
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145 | done</literal>
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146 |
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147 | EOF
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148 |
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149 | chmod +x /usr/sbin/remove-la-files.sh</userinput></screen>
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150 |
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151 |
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152 | </sect2>
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153 |
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154 | </sect1>
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