I wrote the other day about porting software to Linux. I talked about some of the differences between the platforms in terms of the implementation of some well-known C library functions, and hinted at some other incompatibilities. Well, now I’m going to write about some of the other issues I encountered.
There are a number of security-oriented libc functions originating in OpenBSD which are very useful but have had varying degrees of uptake from other OSes. The classic examples are the well-known strlcat and strlcpy functions. As is discussed in this paper, these functions offer a less error-prone interface (specifically in the realm of truncation detection) compared to the strncat/strncpy ANSI C functions. Although they’ve been integrated into to at least Solaris, FreeBSD and NetBSD libc’s, for some bizarre reason they are not included in GNU libc. An additional OpenBSD function I make use of is strtonum. The issue here is that for my software to build on platforms other than OpenBSD, I must include copies of these functions and build them on platforms which don’t already have them. This leads quickly to the need for a way of dynamically detecting at build time whether these functions are available on the host system. Traditionally, the solution to this situation has been to use GNU Autoconf. However, I’ve never been a big fan of autoconf, mostly since its so complicated and tricky to get working with your project. Many people have been dissatisfied with autoconf though, and so alternatives now exist.
Much as I like the simplicity and ubiquity of make, I didn’t fancy implementing all the function call dependency checking in it. Furthermore, I am only familiar with the BSD flavour of make, and didn’t have much inclination to port my makefile over to other platforms. So I decided that I would try out one of the contemporary build systems. I came across something called SCons. I read the documentation and liked it because it seemed to make the tricky things pretty easy. Additionally, its written in Python - which I quite like - and seems to be pretty portable. At least, there are packages for OpenBSD, Linux and Windows.
I actually ended up with two different build systems. A BSDmakefile which will build my application under OpenBSD with no dependencies beyond the base install, and an SConstruct file for all the other platforms - requiring the presence of SCons. I’ve tested the SConstruct build under both Ubuntu and Centos Linux and it works great. I hope to add support for Solaris and Mac OS X in the near future - as soon as I get access to these operating systems.
Tags: BitTorrent, C, Linux, OpenBSD, Porting, UNIX
Related posts: