Creating bindings for C libraries

Overview

This page describes how to create pascal bindings for C libraries. Normally Pascal can not use C libraries directly. You have to create for every C function, type, variable a pascal translation. There is the h2pas tool, which can automatically translate many common C things. And there is a GUI for Lazarus using h2pas and other tools to automate the creation, so that if the bindings needs to be updated you don't have to restart all over.

Work flow

• Fetch the C header files you want to translate.
• Create a working directory and give your bindings a name
• Create a new h2pas project with the h2pas wizard.
• add the .h files to the project
• setup the h2pas options
• run the wizard
• fix errors by adding text tools and run the wizard again
• when h2pas runs without errors, test compilation and add optional tools to beautify the output
• write some test programs to test your bindings
• publish your bindings on lazarus-ccr or Free Pascal

Install tools

The h2pas tool comes with every normal fpc installation.

Install the h2paswizard package in the Lazarus IDE. Go to "Components -> Configure installed packages ...", select from the right list the H2PasWizard package and click 'Install selection', then 'Save and rebuild IDE'. Restart the IDE and you get a new menu entry: Tools -> h2pas

Fetch C header files

The C header files .h describes the interface of a C library. They are normally not provided with the library. You have to get the sources or the development package of the library. For example the C header files of the gtk libraries are in the package gtk+-devel.

Example: MPICH2

Download the mpich2-1.0.3.tar.gz from http://www-unix.mcs.anl.gov/mpi/mpich2/ and unpack them. The .h files are under mpich2-1.0.3/src/include.

Create a working directory and name your bindings

Create a directory with a useful name. A name should not contain special characters, like spaces, umlaute, points or commas.