1 <?xml version="1.0" encoding="UTF-8"?>
2 <section id="autotools_class" xreflabel="autotools class">
3 <title>autotools class</title>
5 <para>Autotools is one of the most commonly seen configuration methods for
6 applications. Anything that uses the standard <command>./configure; make;
7 make install</command> sequence is using autotools. Usually the configure
8 script will support a large number of options to specify various
9 installation directories, to disable and/or enable various features and
10 options to specify search paths for headers and libraries.</para>
12 <para>The autotools class takes care of all of the details for you. It
13 defines appropriate tasks for <emphasis>configure</emphasis>,
14 <emphasis>compile</emphasis>, <emphasis>stage</emphasis> and
15 <emphasis>install</emphasis>. At it's simplest adding an inherit for the
16 autotools class is all that is required. The netcat recipe for example
17 is:<screen>DESCRIPTION = "GNU Netcat"
18 HOMEPAGE = "http://netcat.sourceforge.net"
20 MAINTAINER = "Your name <yname@example.com>"
21 SECTION = "console/networking"
24 SRC_URI = "${SOURCEFORGE_MIRROR}/netcat/netcat-${PV}.tar.bz2"
26 inherit autotools</screen>The header is defined, the location of the source
27 code and then the inherit. For the simplest cases this is all that is
28 required. If you need to pass additional parameters to the configure script,
29 such as for enabling and/or disabling options, then they can be specified
30 via the <command>EXTRA_OECONF</command> variable. This example from the lftp
31 recipe shows several extra options being passed to the configure
32 script:<screen>EXTRA_OECONF = "--disable-largefile --disable-rpath --with-included-readline=no"</screen>If
33 you define your own tasks for <emphasis>configure</emphasis>,
34 <emphasis>compile</emphasis>, <emphasis>stage</emphasis> or
35 <emphasis>install</emphasis> (via <command>do_<taskname></command>)
36 then they will override the methods generated by the autotools class. If you
37 need to perform additional operations (rather than replacing the generated
38 operations) you can use the <command>do_<task>_append</command> or
39 <command>do_<task>_prepend</command> methods. The following example
40 from the conserver recipe shows some additional items being
41 installed:<screen># Include the init script and default settings in the package
42 do_install_append () {
43 install -m 0755 -d ${D}${sysconfdir}/default ${D}${sysconfdir}/init.d
44 install -m 0644 ${WORKDIR}/conserver.default ${D}${sysconfdir}/default/conserver
45 install -m 0755 ${WORKDIR}/conserver.init ${D}${sysconfdir}/init.d/conserver
49 <title>oe_runconf / autotools_do_configure</title>
51 <para>Autotools generates a configuration method called
52 <command>oe_runconf</command> which runs the actual configure script, and
53 a method called <command>autotools_do_configure</command> which generates
54 the configure file (runs automake and autoconf) and then calls
55 <command>oe_runconf</command>. The generated method for the
56 <emphasis>configure</emphasis> task, <command>do_configure</command>, just
57 calls the <command>autotools_do_configure</command> method.</para>
59 <para>It is sometimes desirable to implement your own
60 <command>do_configure</command> method, where additional configuration is
61 required or where you wish to inhibit the running of automake and
62 autoconf, and then manually call <command>oe_runconf</command>.</para>
64 <para>The following example from the ipacct recipe shows an example of
65 avoiding the use of automake/autoconf:<screen>do_configure() {
67 }</screen>Sometimes manual manipulations of the autotools files is required
68 prior to calling autoconf/automake. In this case you can defined your own
69 <command>do_configure</command> method which performs the required actions
70 and then calls <command>autotools_do_configure</command>.</para>
74 <title>Presetting autoconf variables (the site file)</title>
76 <para>The autotools configuration method has support for caching the
77 results of tests. In the cross-compilation case it is sometimes necessary
78 to prime the cache with per-calculated results (since tests designed to
79 run on the target cannot be run when cross-compiling). These are defined
80 via the site file(s) for the architecture you are using and may be
81 specific to the package you are building.</para>
83 <para>Autoconf uses site files as definied in the
84 <command>CONFIG_SITE</command> variable, which is a space seperate list of
85 files to load in the specified order. Details on how this variable is set
86 is provided in the <xref linkend="siteinfo_class" /> (the class
87 responsbile for setting the variable) section.</para>
89 <para>There are some things that you should keep in mind about the caching
90 of configure tests:</para>
94 <para>Check the other site files to see if there any entries for the
95 application you are attempting to build.</para>
97 <para>Sometimes entries are only updated for the target that the
98 developer has access to. If they exist for another target then it may
99 provide a good idea of what needs to be defined.</para>
103 <para>Sometimes the same cache value is used by multiple
106 <para>This can have the side effect where a value added for one
107 application breaks the build of another. It is a very good idea to
108 empty the site file of all other values if you are having build
109 problems to ensure that none of the existing values are causing
114 <para>Not all values can be stored in the cache</para>
116 <para>Caching of variables is defined by the author of the configure
117 script, so sometimes not all variables can be set via the cache. In
118 this case it often means resorting to patching the original configure
119 scripts to achieve the desired result.</para>
123 <para>All site files are shell scripts which are run by autoconf and
124 therefore the syntax is the same as you would use in sh. There are two
125 current methods of settings variables that is used in the existing site
126 files. This include explicitly settings the value of the variable:<screen>ac_cv_sys_restartable_syscalls=yes</screen>and
127 conditionally setting the value of the variable:<screen>ac_cv_uchar=${ac_cv_uchar=no}</screen>The
128 conditional version is using shell syntax to say "<emphasis>only set this
129 to the specified value if it is not currently set</emphasis>". The
130 conditional version allows the variable to be set in the shell prior to
131 calling configure and it will then not be replaced by the value from the
135 <para>Site files are applied in order, so the application specific site
136 files will be applied prior to the top level site file entries. The use
137 of conditional assignment means that the first definition found will
138 apply, while when not using conditionals the last definition found will
142 <para>It is possible to disable the use of the cached values from the site
143 file by clearing the definition of <command>CONFIG_SITE</command> prior to
144 running the configure script. Doing this will disable the use of the site
145 file entirely. This however should be used as a last resort. The following
146 example from the db recipe shows an example of this:<screen># Cancel the site stuff - it's set for db3 and destroys the