use autotools to make project

1.1.  Write sources

1. Create an empty directory called tut_prog and enter in it.
2. In this new directory, create a new file named main.c containing:

Example 3-1   main.c:

#include <stdio.h> 
	
int main()
{
	printf("Hello world!/n");
	return 0;
}

1.2.  Run Autoconf

1. Write the following in a file named configure.ac :

Example 3-2   minimal configure.ac:

AC_INIT([Tutorial Program], 1.0)
AM_INIT_AUTOMAKE
AC_PROG_CC
AC_CONFIG_FILES(Makefile)
AC_OUTPUT

The configure template script could be named configure.in . It is the name used in older version (before 2001) of Autoconf . Nevertheless, it is recommended to use configure.ac because the .in extension is already used by files processed by configure and generated by Automake : Makefile.in and autoheader : config.h.in .

AC_INIT, AM_INIT_AUTOMAKE, etc... are M4 macros. M4 is a macro expanding software used by Autotools ; we don't need to know about it. When Autoconf will process this configure.in, the macros will be expanded and we will get a fresh huge configure script.

AC_INIT

Is the first mandatory macro. We need to indicate the name of the project and its version.

AM_INIT_AUTOMAKE

Initialize environment for Automake . It is needed in all projects using Automake .

AC_PROG_CC

Determine the C compiler to use.

AC_CONFIG_FILES

Create each file by copying the corresponding template file (with .in extension) and substituting the output variable values.

AC_OUTPUT

Marks the end of the configure template.

The use of some macros has changed between different versions of Autoconf :

• The package name and version was defined as arguments of AM_INIT_AUTOMAKE instead of AC_INIT.
• AC_OUTPUT was getting the list of generated files instead of using the additional macro AC_CONFIG_FILES.

Autoconf only knows its own macros but read additional ones in a file named aclocal.m4 . These macros are used to extend Autoconf , it includes Automake macro (starting with AM_) and other third party macros. For instance, if you develop a library called foo, you might want to write an AC_CHECK_FOR_FOO macro so that developers using your library can check for its presence using Autoconf .

aclocal scans configure.ac and create an aclocal.m4 file which contains the macros mentioned in configure.ac . aclocal is part of the Automake package and search by default in Automake macros and in a system path typically /usr/share/aclocal .

1. Launch aclocal . It will create a new file named aclocal.m4 in the current directory.
2. Launch autoconf . It will create the configure script configure .

On my system, I actually get an extra directory called autom4te.cache . That is for Autoconf internal purposes. You do not need to care about it.

1.3.  Run Automake

1. Write the following in a file named Makefile.am :

Example 3-3   minimal Makefile.am:

bin_PROGRAMS = tut_prog			
tut_prog_SOURCES = main.c

In Makefile.am are the very essential data needed to build the project: the target program, called tut_prog, will be put in a $prefix/bin/ directory; to build it we need main.c. Note that we don't specify how that will be built: Automake will figure it out. We haven't even mentioned the compiler in this pre-makefile.

Makefile.am will be processed by Automake ; the result will be a Makefile.in. This Makefile.in is close to being a real makefile, but it contains variable names which will be replaced when the configure script will run, resulting in a real makefile (called Makefile). For instance, configure will write in the final Makefile what compiler to use (it is the compiler it found using the AC_PROG_CC macro).

1. Run the command automake --add-missing --foreign . It will create a new file named Makefile.in as expected. Moreover, due to the switch --add-missing you get a few links to scripts necessary for building the project: depcomp , install.sh and missing . The other option --foreign tells to Automake that you don't want to follow GNU standard and you don't need mandatory documentation files: INSTALL , NEWS , README , AUTHORS , ChangeLog and COPYING . I have used it here to keep the number of created file to a minimum but else it is a good idea to provide these files, you can start with empty files.

1.4.  Build project

1. Run now the new configure script: ./configure . You get the following output and it create the makefile for your program.

   checking for a BSD-compatible install... /usr/bin/install -c
   checking whether build environment is sane... yes
   checking for a thread-safe mkdir -p... /bin/mkdir -p
   checking for gawk... gawk
   checking whether make sets $(MAKE)... yes
   checking for gcc... gcc
   checking for C compiler default output file name... a.out
   checking whether the C compiler works... yes
   checking whether we are cross compiling... no
   checking for suffix of executables... 
   checking for suffix of object files... o
   checking whether we are using the GNU C compiler... yes
   checking whether gcc accepts -g... yes
   checking for gcc option to accept ISO C89... none needed
   checking for style of include used by make... GNU
   checking dependency style of gcc... gcc3
   configure: creating ./config.status
   config.status: creating Makefile
   config.status: executing depfiles commands
   

2. Run now make , to build your program. You get the following output and a new tut_prog executable

   gcc -DPACKAGE_NAME=/"Tutorial/ Program/" -DPACKAGE_TARNAME=/"tutorial-program/"   /
           -DPACKAGE_VERSION=/"1.0/" -DPACKAGE_STRING=/"Tutorial/ Program/ 1.0/"     /
           -DPACKAGE_BUGREPORT=/"/" -DPACKAGE=/"tutorial-program/" -DVERSION=/"1.0/" /
           -I.     -g -O2 -MT main.o -MD -MP -MF .deps/main.Tpo -c -o main.o main.c
   main.c: In function ‘main’:
   main.c:5: warning: return type of ‘main’ is not ‘int’
   mv -f .deps/main.Tpo .deps/main.Po
   gcc  -g -O2   -o tut_prog main.o
   

3. Now, if you can write in /usr/local/bin , run make install to install your program. Else you need to log as root before or use sudo and run sudo make install . You should get.

   make[1]: Entering directory `/home/seb/Projects/Tutorial'
   test -z "/usr/local/bin" || /bin/mkdir -p "/usr/local/bin"
     /usr/bin/install -c 'tut_prog' '/usr/local/bin/tut_prog'
   make[1]: Nothing to be done for `install-data-am'.
   make[1]: Leaving directory `/home/seb/Projects/Tutorial'
   

   Then, if /user/local/bin is in your path, you can run your program from everywhere.

1.5.  Clean project

1. The program is installed, so you can clean the build directory running make clean . It removes all object files and the program but not the makefiles.

   test -z "tut_prog" || rm -f tut_prog
   rm -f *.o
   

   You can still run the program installed in /user/local/bin .

2. To remove the installed program, run make uninstall . Like for the installation, you need to use have the writing right in the directory or use su or sudo .

   rm -f '/usr/local/bin/tut_prog'
   

1.6.  Generate project

Running aclocal , automake and autoconf one by one is fine for a tutorial to understand exactly what's happen. But, for a real work, it's a bit tedious especially because there are other tools those could be needed like autoheader , autopoint or libtoolize . After creating the project, the makefiles generated by configure should take care of regenerating configure and all Makefile.in . Anyway, this lets a room for improvement and there are even two responses to this:

autoreconf

It is another tool part of the Autoconf package which is running all scripts in the right order. To start a new project, you can just run autoreconf --install and it will call all necessary commands.

autogen.sh

It is a script not part of Autotools , that it doing the same thing. There is one named gnome-autogen.sh which comes with GNOME common development package but other project can write their own ones.