source: introduction/important/la-files.xml@ 4fa85cb8

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Last change on this file since 4fa85cb8 was 4fa85cb8, checked in by Bruce Dubbs <bdubbs@…>, 5 years ago

Update graphviz url

git-svn-id: svn://svn.linuxfromscratch.org/BLFS/trunk/BOOK@19593 af4574ff-66df-0310-9fd7-8a98e5e911e0

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE chapter 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
8<sect1 id="la-files" xreflabel="Libtool archive (.la) files">
9 <?dbhtml filename="la-files.html"?>
10
11 <sect1info>
12 <othername>$LastChangedBy$</othername>
13 <date>$Date$</date>
14 </sect1info>
15
16 <title>About Libtool Archive (.la) files</title>
17
18 <!-- section g : 'Others' in longindex.html -->
19 <indexterm zone="la-files">
20 <primary sortas="g-la-files">Library archive (.la) files</primary>
21 </indexterm>
22
23 <sect2 role="package">
24 <title>Files with a .la extention</title>
25
26 <para>
27
28 In LFS we installed a package, libtool, that is used by many packages to
29 build on a variety of Unix platforms. This includes platforms such as
30 AIX, Solaris, IRIX, HP-UX, and Cygwin as well as Linux. The origins of
31 this tool are quite dated. It was intended to manage libraries on
32 systems with less advanced capabilities than a modern Linux system.
33
34 </para>
35
36 <para>
37
38 On a Linux system, libtool specific files are generally unneeded.
39 Normally libraries are specified in the build process during the link
40 phase. Since a linux system uses the <ulink
41 url="https://en.wikipedia.org/wiki/Executable_and_Linkable_Format">
42 Executable and Linkable Format (ELF)</ulink> for executables and
43 libraries, information needed to complete the task is embedded in the
44 files. At run time the program loader can query the appropriate files
45 and properly load and execute the program.
46
47 </para>
48
49 <para>
50
51 The problem is that libtool usually creates one or more text files for
52 package libraries called libtool archives. These small files have a
53 ".la" extention and contain information that is similar to that embedded
54 in the libraries. When building a package that uses libtool, the
55 process automatically looks for these files. If a package is updated
56 and no longer uses the .la file, then the build process can break.
57
58 </para>
59
60 <para>
61
62 The solution is to remove the .la files. However there is a catch.
63 Some packages, such as <xref linkend='imagemagick'/>, use a libtool
64 function, lt_dlopen, to load libraries as needed during execution and
65 resolve their dependencies at run time. In this case, the .la files
66 should remain.
67
68 </para>
69
70 <para>
71
72 The script below, removes all unneeded .la files and saves them in a
73 directory, /var/local/la-files by default, not in the normal library
74 path. It also searches all pkg-config files (.pc) for embedded
75 references to .la files and fixes them to be conventional library
76 references needed when an application or library is built. It
77 can be run as needed to clean up the directories that may be causing
78 problems.
79
80 </para>
81
82<screen role="root"><userinput>cat &gt; /usr/sbin/remove-la-files.sh &lt;&lt; "EOF"
83<literal># Begin /etc/bashrc
84# Written for Beyond Linux From Scratch
85# by Bruce Dubbs &lt;bdubbs@&lfs-domainname;&gt;
86
87# Make sure we are running with root privs
88if test "${EUID}" -ne 0; then
89 echo "Error: $(basename ${0}) must be run as the root user! Exiting..."
90 exit 1
91fi
92
93# Make sure PKG_CONFIG_PATH is set if discarded by sudo
94source /etc/profile
95
96OLD_LA_DIR=/var/local/la-files
97
98mkdir -p $OLD_LA_DIR
99
100# Only search directories in /opt, but not symlinks to directories
101OPTDIRS=$(find /opt/* -maxdepth 0 -type d)
102
103# Move any found .la files to a directory out of the way
104find /usr/lib $OPTDIRS -name "*.la" ! -path "/usr/lib/ImageMagick*" \
105 -exec mv -fv {} $OLD_LA_DIR \;
106###############
107
108# Fix any .pc files tha may have .la references
109
110STD_PC_PATH='/usr/lib/pkgconfig
111 /usr/share/pkgconfig
112 /usr/local/lib/pkgconfig
113 /usr/local/share/pkgconfig'
114
115# For each directory that can have .pc files
116for d in $(echo $PKG_CONFIG_PATH | tr : ' ') $STD_PC_PATH; do
117
118 # For each pc file
119 for pc in $d/*.pc ; do
120 if [ $pc == "$d/*.pc" ]; then continue; fi
121
122 # Check each word in a line with a .la reference
123 for word in $(grep '\.la' $pc); do
124 if $(echo $word | grep -q '.la$' ); then
125 mkdir -p $d/la-backup
126 cp -fv $pc $d/la-backup
127
128 basename=$(basename $word )
129 libref=$(echo $basename|sed -e 's/^lib/-l/' -e 's/\.la$//')
130
131 # Fix the .pc file
132 sed -i "s:$word:$libref:" $pc
133 fi
134 done
135 done
136done
137
138EOF
139
140chmod +x /usr/sbin/remove-la-files.sh</literal></userinput></screen>
141
142 <para condition="html" role="usernotes">
143 User Notes: <ulink url="&blfs-wiki;/la-files"/>i
144 </para>
145
146 </sect2>
147
148</sect1>
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