Overview

Obtaining software directly from the source code is a common procedure on Unix computers, and generally involves the following three steps:

• Configuring the Makefile : [./configure]
• Compiling the code : [make]
• Installing the executable : [make install]

The challenge of cross-platform is simplified by using GNU's AutoTools

AutoTool : The GNU Build System, also known as the Autotools, is a suite of programming tools designed to assist in making source code packages portable to many Unix-like systems. Autotools consists of the GNU utility programs Autoconf, Automake, and Libtool.

Configuration Files

• Makefile.am
• configure.ac
• Makefile.in
• Makefile

How do they work?

 configure.ac        Makefile.am
      |                  |
 [Autoconf]           [Automake]   
      |                  |
configure script     Makefile.in
      \                  /
       \________________/
               |
         config.status
               |
           Makefile
               |
            [make]
               |
         (Executable)
       

• Source

• Autoconf generates a configure script based on the contents of a configure.ac file which characterizes a particular body of source code.

• The configure script, when run, scans the build environment and generates a subordinate config.status script which, in turn, converts other input files and most commonly Makefile.in into output files (Makefile)

• Automake helps to create portable Makefiles, which are in turn processed with the make utility.

• It takes its input as Makefile.am (programmer-defined file : so that they can write the make commands in developer friendly manner), and turns it into Makefile.in.

• Finally the make program uses Makefile to generate executable programs from source code.

Implementation

• Create configure.ac file
• Create Makefile.am file
• run command aclocal
  • first we need to generate m4 environment for autotools to use
• run command autoconf
  • this command will generate configure script.
• run command automake --add-missing
  • this command will generate Makefile.in file.
• The end user doesn’t need to see our autotools setup, so we can distribute the configure script and Makefile.in without all of the files we used to generate them.
• run command ./configure : to Generate Makefile from Makefile.in
• run command make distcheck : Use Makefile to build and test a tarball to distribute

So on Maintainer's system:

aclocal # Set up an m4 environment
autoconf # Generate configure from configure.ac
automake --add-missing # Generate Makefile.in from Makefile.am
./configure # Generate Makefile from Makefile.in
make distcheck # Use Makefile to build and test a tarball to distribute

On the user's system:

./configure # Generate Makefile from Makefile.in
make # Use Makefile to build the program
make install # Use Makefile to install the program

Git Submodule

Initialize Submodule

To add a submodule

git submodule add -f -b master git@github.com:Vishwas1/democpplib.git lib/helloworld

First, we need to initialize the submodule(s). We can do that with the following command:

git submodule init

Then we need to run the update in order to pull down the files.

git submodule update

To remove a submodule?

• Remove the submodule’s entry in the .gitmodules file.
• Remove the submodule’s entry in the .git/config
• Remove the path created for the submodule by using the command below.

git rm --cached lib/helloworld

To get the HEAD of each submodule

git submodule foreach 'echo $path git rev-parse HEAD'

Generating lib

• cd lib/helloworld
• ./autogen.sh
• ./configure
• make

http://inti.sourceforge.net/tutorial/libinti/autotoolsproject.html

• static vs dynamic library.
• static vs dynamic linking.

Using BOOST library in project

• The Boost C++ Libraries are a collection of modern libraries based on the C++ standard.

references

• Build system
• Makefile.in vs Makefile.am
• Magic behind configure, make, make install