Brief#
- GNU Build System: Automake, Autoconf, Libtool are a suite of programming tools used to make source code packages portable to many Unix-like systems.
Autoconf: automatically generates configure script by scans of existing tree to find its dependencies, that are supposed to work on all kinds of platforms.configure generates a config.h file (from a template) which programs can include to work around portability issues. For example, if HAVE_LIBPTHREAD is not defined, use forks instead.Automake: No need to write lengthy & complex makefiles. just define target, dependencies, flags, etc.-
Libtool: simplifying the building and installation of shared libraries on any Unix-like system. - Autotools can handle cross-platform development smoothly.
Above statements may seem like alien right now. But just go through below example & then read again. You will get what I just said
- Creating following files in empty directory
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| AC_INIT([PackageName], [1.0], [bug-report@address]) # Initialize `Autoconf`. Specify package's name, version & bug-report address.
AM_INIT_AUTOMAKE # Initialize Automake
AC_PROG_CC # Check for a C compiler
AC_CONFIG_HEADERS([config.h]) # Declare config.h as output header
AC_CONFIG_FILES([Makefile src/Makefile]) # Declare Makefile & src/Makefile as output files
AC_OUTPUT # Output all declared files
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Makefile.am#
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| SUBDIRS = src # Build recursively in src directory
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src/Makefile.am#
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| bin_PROGRAMS = hello # "hello" is target & will be installed in bindir (as specify "bin_")
hello_SOURCES = main.c # Dependencies of target hello is main.c
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src/main.c#
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| #include<stdio.h>
int main()
{
puts("Hello World !");
return 0;
}
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Directory Structure#
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| $ ls -R
.:
configure.ac Makefile.am src
./src:
main.c Makefile.am
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Build Package#
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| $ autoreconf --install
$ ./configure --prefix=$(pwd)
$ make
$ bin/hello
Hello World !
$
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At this stage, there are a lot of other files are generated as follows :
Makefile.in, config.h.in, config* : expected configuration templates.aclocal.m4: definitions for third-party macros used in configure.ac.depcomp, install-sh, missing: auxiliary tools used during the build.autom4te.cache/: Autotools cache files.
Understand Build Package Procedure#
Step 1: autoreconf --install#
autoreconf is a helper that knows how to call autoconf, autoheader, aclocal, automake, libtoolize, autopoint, etc tools in the right order.
Behind autoreconf
aclocal: Scan configure.ac for uses of third-party macros, and gather definitions in aclocal.m4.autoconf: Create configure from configure.ac & aclocal.m4.autoheader : Create config.h.in from configure.ac.automake --add-missing: Create Makefile.in s from Makefile.am s, configure.ac & aclocal.m4. --add-missing option will add required file(like config.guess, config.sub, missing, depcomp, install-sh, etc) to carry out build process.
Note: Run libtoolize, If you use LT_INIT to create a shared library with libtool in configure.ac, otherwise you will get error as configure.ac:[LINE]: error: required file './ltmain.sh' not found.
configure will create Makefiles from Makefile.ins
Step 3: make & make install#
- Finally
make & make install - Do all things for you
Generalise Idea#
- Practically, You do not have to remember the interaction of all tools, just call
autoreconf yourself and let it deal with all the lower-level tools. autoreconf is your friend. You only need a rough idea of the purpose of each tool to understand errors.
GNU Autoconf#
autoconf Create configure from configure.ac.autoheader Create config.h.in from configure.ac.autoreconf Run all tools in the right order.autoscan Scan sources for common portability problems, and related macros missing from configure.ac.autoupdate Update obsolete macros in configure.ac.ifnames Gather identifiers from all #if/#ifdef/... directives.autom4te The heart of Autocon. It drives M4 and implements the features used by most of the above tools. Useful for creating more than just configure files.
GNU Automake#
automake Create Makefile.in from Makefile.am and configure.ac.aclocal Scan configure.ac for uses of third-party macros, and gather definitions in aclocal.m4.
Libtool Helps manage the creation of static and dynamic libraries on various Unix-like operating systems
Distributing Packege#
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| $ make distcheck
=================================================
packagename-1.0 archives ready for distribution:
packagename-1.0.tar.gz
=================================================
|
- At the end of command execution you will find
packagename-1.0.tar.gz in same folder.
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| AC_INIT([PackageName], [1.0], [bug-report@address])
AM_INIT_AUTOMAKE([foreign])
LT_INIT # Used to initialize libtool to create shared library
AM_MY_MACRO="-I ./" # Delacring Custome Macro
AC_SUBST([AM_MY_MACRO]) # Passing Custome Macro to Makefile.am
AC_PROG_CC
AC_CONFIG_HEADERS([config.h])
AC_CONFIG_FILES([Makefile sum/Makefile src/Makefile])
AC_OUTPUT
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Makefile.am#
src/main.c#
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| #include
int main()
{
printf("sum(0,1) = %d\n", sum(0,1));
return 0;
}
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src/Makefile.am#
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| bin_PROGRAMS = sum
sum_SOURCES = main.c
sum_LDADD = ../sum/libsum.la # add & link sum against libsum.so
sum__LDFLAGS = $(AM_MY_MACRO) # Macro Passed By configure.ac
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sum/sum.c#
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| #include<stdio.h>
int sum(int a, int b)
{
return a + b;
}
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sum/Makefile.am#
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| lib_LTLIBRARIES = libsum.la
libsum_la_SOURCES = sum.c
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Directory Structre#
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| $ ls -R
.:
configure.ac Makefile.am src sum
./src:
main.c Makefile.am
./sum:
Makefile.am sum.c
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Build Package#
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| $ autoreconf --install
$ ./configure --prefix=$(pwd)
$ make install
$ ./bin/sum
sum(0,1) = 1
$
$ ldd ./bin/sum
linux-vdso.so.1 => (0x00007fff606ac000)
libsum.so.0 => /home/vishal/asdf/lib/libsum.so.0 (0x00007fdcf43a6000)
libc.so.6 => /lib64/libc.so.6 (0x00007fdcf3fcd000)
/lib64/ld-linux-x86-64.so.2 (0x00007fdcf45a9000)
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- At the end of
make install, there are two folders named lib & bin having a shared library in lib & executable in bin.
What Next ?#
- This is just short introduction of How Autotools help us ! There are lot to discover about its competitors like CMake, Scons, etc.
Sources#
- Autotools
- GNU Build System
- Automake