Main sources of Wine complexity

[Damjan Jovanovic]

On Mon, Jun 10, 2013 at 2:34 PM, Ivan <ivdivd0 at gmail.com> wrote:
> (short summary: why is emulation of Windows environment so difficult).
>
> First of all, my apologies if this is an off-topic question for this list
> but I hope it will be useful for others in the similar situation.
>
> I need to port fairly large WinAPI-heavy application to Linux. After some
> googling it becomes clear that there's nothing except for Wine/Winelib which
> is *huge*. However for at least most basic WinAPI functions it looks fairly
> easy to just re-implement it via Boost/STL/libc/Linux syscalls. Why there's
> nothing small like this already? Why only Wine with like 3 millions LoC and
> run-time dependencies?
>
> Is the approach described above make some sense for at least most common
> functionality (threading, IPC, file operations) w/o things like UI, graphics
> and registry. For instance, we need to either re-implement around 200 WinAPI
> functions (mostly events, mutexes, semaphore, sockets, file and folder
> operations) or to rewrite the entire thing from scratch. Using Winelib
> directly is not an option due to the nature of the app. Any help/advices are
> greatly appreciated.
>
> Thank you.

* no direct API conversion is always possible, eg. there is no
WaitForMultipleObjects() equivalent in pthreads, which means the
entire synchronization API has to be reimplemented.
* Windows and *nix file systems differ and so does behavior of file
APIs (eg. case sensitivity, attributes such as hidden files, etc.)
* complex interdependencies and interactions between APIs exist (eg.
sockets can be made into handles which can then use various
synchronization APIs, and socket I/O notifications can get delivered
into the UI message loop...).
* the Windows API has a ~28 year history and is enormous.
* the Windows API doesn't follow a standard, it is a de-facto standard
with questionable documentation and only Wine's regression tests to
determine exact behavior.
* Wine is very small compared to Windows itself.
* Windows has lots of dependencies too, they're just less
direct/obvious (eg. USER/GDI in the kernel, as opposed to Wine using
X11 libs)

Can't you just use a small subset of Winelib that covers everything you need:
* delete all the DLLs that aren't used by your app
* fiddle with ./configure options to disable dependencies you don't need

There is also Cedega and other Wine spin-offs, but I think there's
even less hope there.

Damjan