Porting software to MINIX from Linux or FreeBSD is non-trivial in most cases, but not exactly rocket science either. A major part of the work often has to do with altering/extending makefiles or build scripts. Recoding major parts of a piece of software generally is required for only software that does some or all of its work in kernel space. You can help MINIX by porting packages!
For starters, read POSIX and MINIX, Programming in MINIX, and Pkgsrc Guide. The Wishlist may also be helpful for identifying functionality that hasn't been implemented in Minix yet. The information shared on those pages is partially redundant.
This page shall serve as an entry-point for developers wishing to port POSIX applications (e.g., from Linux) to MINIX 3. A fair number of applications already were ported, thanks to the efforts of our contributors. Before you begin porting any application, check to see if it's already been ported. A list of packages known to compile and work is in pkgsrc in a file called limited_list.pbulk.
If the application hasn't been ported yet and it doesn't work 'out of the box' via pkgsrc, follow this recipe:
pkgsrc is configured with the right settings to make source code happy. The right defines are set (-D_NETBSD_SOURCE -D_POSIX_SOURCE -D_COMPAT_MINIX) with the right additional libraries (-lcompat_minix -lminlib) as well as dependency checking and patches. So start off on the right foot and start your porting effort with pkgsrc.
As AST points out in his very recommended talk at FOSDEM, most configure scripts are buggy. Have a look at this Tutorial on debugging configure.
At the least, you probably will need to add detection of the uname string returned by MINIX. That case often can be handled in the same way as other POSIX systems, such as Linux and BSD.
At first, do not implement missing library functions, but only declare them in header files. That way, you will be able to see which are the most important missing functions, before doing much work. Based on the missing functions, it then is possible to determine whether or not porting is feasible. For example, it might not be possible to port programs which use threads or memory-mapped files, without fundamental changes. Such ports can be delayed until the required functionality is available in MINIX. In that case, you may add both the port and the missing features to the wish list, specifying that the unavailability of the latter blocks the former.
If the program can be made to work without the functions/headers, it is usually best to add autoconf checks for the features/headers and then using the generated macros (example: HAVE_SETPGID, etc). This solution is much better than simply adding ifdef
__minix everywhere. Using the autoconf feature checks will allow the packages to take advantage of new features in Minix when they are introduced with a simple re-compile (instead of another set of patches to remove ifdef
If you added declarations, as recommended in the previous section, eventually you will receive a linker error showing which symbols were used but not defined. That would be the time to implement those missing library functions, preferably in such a way that they easily can be moved into the MINIX libraries, later on. The man pages on the Open Group website are a good source of information about what such calls should do exactly.
Warnings emitted by the C compiler are a good source of information on what might be wrong in the
program you ported. It is preferable to eliminate all warnings, as that might save you a great deal
of time on testing. Do attempt to compile your program with the
-W flags, for maximum compiler assistance.
Testing and fixing bugs can take considerable time for software with poor portability and software that uses features missing in MINIX. Often, programs come with test suites that provide a good starting point.
__minixpreprocessor symbol indicates when C code is being compiled on MINIX – avoid
__minixif Minix might one day get the ability to use the code you are blocking out.
-funsigned-char” was added to the CFLAGS.