Vala + Autotools example

As a part of learning great Vala language I decided to implement the simplest possible example of Vala console application e.g. a simple calculator program that parses user input and evaluates the expression.

The project is going to have:

• Unit tests that tests API level functions.
• A usage example of libraries that can be used both for unit tests and for the program itself.
• Small and readable Autotools code. The project should be reusable by anyone else as a skeleton for their own project.

The code of the project you can find at my github page.

I am not going to describe Autotools plumbing code. It is pretty much the same as any other Autotools based project has. I recommend to read following article if you are interested in the Autotools details.

Let’s look at the Vala-specific code instead.

• configure.ac The key file for autoconf tool.It has several interesting pieces:

AM_PROG_VALAC – Autotools already has Vala support and the given macros enables it. After you added it Automake knows what to do with *.vala source files – it invokes valac compiler.

pkg_modules="glib-2.0 >= 2.24.1
             gobject-2.0 >= 2.24.1"
PKG_CHECK_MODULES(CALCULATOR, [$pkg_modules])
AC_SUBST(CALCULATOR_CFLAGS)
AC_SUBST(CALCULATOR_LIBS)

This code checks in your system libraries needed to compile Vala C files. It also evaluates paths to header and shared library files – later these variables will be used for compilation.

• src/calculator.vala is a core file that contains most of the calculator logic. Later we are going to test this functionality.
• src/main.vala this is thin wrapper for the calculator library. It has main() method and this file is needed for creating end-used console application.
• src/Makefile.am This is the most interesting file in the project. Let’s look at it closely.

bin_PROGRAMS = calculator
noinst_LTLIBRARIES = libcalculator.la

Here we declare that this directory has 1 library and 1 binary file.

libcalculator_la_SOURCES = calculator.vala
libcalculator_la_VALAFLAGS = --library calculator -H calculator.h

Calculator library consists of 1 file – calculator.vala but you can as many *.vala files as you want. The second line declares that make should generate calculator.vapi file and *.h that is also needed for compilation.  *.vapi file is kinda ‘header’ file for Vala compier the *.vapi file contains Vala classes declaration, but does not have any implementation. So the library generates 3 files – *.la, *.vala, *.h.

calculator_SOURCES = main.vala
calculator_LDADD = libcalculator.la $(CALCULATOR_LIBS)
calculator_VALAFLAGS = calculator.vapi

This generates output binary file, our console application that we develop. Its source file is main.vala – wrapper around the library. _LDADD adds calculator library as a dependency, _VALAFLAGS  passes *.vapi file to valac compiler.

• test/calculator_test.vala. This is a unit (aka API level) test
• test/Makefile.am

Run ./autogen.sh and then ‘make’ to build ./src/calculator console application. If you run ‘make check’ you’ll see test results

make  check-TESTS
/calculator/add: OK
/calculator/minus: OK
/calculator/multiply: OK
PASS: calculator-test

PS Things that I might add in the future:

• Valadoc documentation generation. It is nice to have API in readable format so you can upload it to the project server.
• CMake example. I don’t have a lot of experience in autotools so in this project I learned Autotools in addition to Vala language. As of my taste Autotools have a lot of black magic. I still do not understand how the build system works for my project. Some people say that CMake easier to learn that Autotools. So similar example for CMake could be a good lesson as well.