Porting a large C project from Unix to Windows

Question

So, I have a large C project that was built entirely on Unix (SPARC Solaris). me and several others have begun to revisit it because their was some interest in a windows build.

none of us have done this with a project of such size, so for starters, has anyone ported something from unix to windows and could maybe give me some pointers or how they did it.

our first step on our plan was to decide on a compiler/dev environment.

it seems that our options are MS Visual Studio, Cygwin, mingw/gcc, and Windows Services for UNIX (SFU).

we are on a fairly short timetable so we want to rewrite as little code as possible.

so, Deciding on a compiler.

Another issue is that the code does use POSIX thread commands (pthread, etc)

we would prefer to compile natively, not using some sort of layer between the executable and the OS. unfortunatly with the pthread calls in our code, this may not be possible.

I believe both Cygwin and SFU do just that. Cygwin has a .dll that must be included in compiled code to work. I am not sure about SFU, any information about that would be greatly appreciated. It seems like it would be a good option but was developed to allow for UNIX compiled software to run on a windows machine with SFU, not any old windows box.

mingw does have the ability to create native exes, but lacks the POSIX support.

So, can anyone give me any more information, suggestions, knowledge on any of these compilers in this context. or any experience they have with this sort of thing, it is greatly appreciated.

Answer 1

Short timetable? CygWin, plain and simple.

Despite your preference to not use a layer, that's going to provide the fastest path and you don't seem to indicate that the timeframe requirement is flexible.

We've ported both command-line and X-based UNIX programs to Windows using CygWin with minimal hassle.

Answer 2

If the code is (at least mostly) portable and the only major issue is the use of pthreads, you might want to use the Pthreads Win32 library. While incomplete, it's sufficiently complete and accurate to deal with most pthreads code I've tried it with. While normally built as a DLL, this can also be built as a static library to avoid creating an extra dependencies in your executable.

That, of course, leaves everything else to port -- but you haven't said enough to even guess whether porting the rest within your timeframe is at all reasonable.

Answer 3

Cygwin is likely the fastest path to a working executable. However it will leave you with some interesting distribution choices. Most obviously, cygwin.dll becomes a dependency. Its licensed GPL, unless you pay money to buy commercial use rights.

Cygwin is not particularly friendly to an ordinary Windows user. Its goal is to provide a full POSIX experience on Windows, supplying a shell, all the familiar *nix utilities, and even a port of X. However, it also remaps the Windows disk drive naming into a POSIX-like file system. I've never attempted to distribute an application built for Cygwin to machines that don't already have a full Cygwin installation. I will note that to my knowledge none of the big well-known open-source applications with Windows ports are based on Cygwin.

If the only hard POSIX dependency you have is pthreads, then that is solvable. There is a pthreads port built on native Windows threads that works well with MinGW. IIRC, it is even distributed along with MinGW, or at least is one of their core supported packages.

If the rest of your handling of file names is largely as opaque strings, you may not even need to care about changing / to \. The Windows API is generally happy to treat either character as a path separator, even mixed in the same name. It is the CMD.EXE and early DOS convention of using / for command line options that prevents the use of / for pathnames at the command prompt, not the underlying Windows API.

For tools that might make porting your build process easier, check out the MSYS component of MinGW. It provides a lightweigh fork from the Cygwin environment in which enough *nix utilities are available to generally run ./configure and similar processes.

In addition, the GnuWin32 project has ports of a large number of utilities and libraries that are all built to run as native Windows applications without unusual dependencies.