Lua unit tests crash on win32/VS2008 build

I created a unit test using boost unit test framework to isolate the problem (in lp:~jarih/widelands/fix-lua-msvc) and interestingly, also GCC build will crash in the unit test. Same fix applied to both platforms.

Method dispatching started to work, but properties still need some work.

jari, I have deep respect for the work you put into this. There is quite a lot of magic in my Lua wrappings and I assume it is hard to get those bugs vanquished. Keep up the good work!

Also properties are now fixed in the branch. Unit tests pass under windows and linux.

When considering merging to trunk, biggest issue is unit test support as it propably clashes with spice-up-cmake branch.

There is currently no need to rush the merge. Have you managed to solve all problems now? Can you enlighten me how you did this?

All problems are solved. both multiple inheritance and virtual bnase classes are now supported on linux/gcc and windows/msvc. Basic principle in the fixes was to ensure that whenever something is reinterpred_cast:ed to void* and stored to lua tables, it's always casted to exactly same type when it's casted back from void*.

Fix contained three parts.

First issue was that when LuaInterface_Impl* is stored to lua registry, it must be casted first to LuaInterface*. This is already in trunk, as it's very simple fix and practically required for launching widelands.exe with msvc2008.

Second issue was to fix method dispatching to retrive method pointer using correct type and was easily fixed by additional template parameter for parent type in m_method_dispatch.

Last part was to fix properties and this required more work as it did not employ dispatching. Therefore I implemented dispatching system for it. Intead of storing lightuserdata with pointer to property structure to metatable, metatable now contains a table with lightuserdata for getter and setter as well as cfunction for dispatching the property. Templated dispatching function stores type information for parent type so that when property is accessed, types are same is when it was stored.

I tried to reuse m_method_dispatch for also properties, but I could not figure out how to use cclosure correctly. So I opted for more straightforward version. m_property_disptach is practically a copy of m_method_dispatch with different place to get member function pointer. If you can come up with cleaner solution to pass getter/setter to dispatching function, then by all means have a try. Unit tests should validate that everything works.

Additionally I implemented unit test support to better debug the problems. There were some tricks needed to prevent linking with widelands main.cc or SDL_main:
 - WL_MAIN_SRCS contained main.cc due to greedy globbing. This was fixed by removing main.cc after globbing.
 - SDL_LIBRARY contained SDL_main.lib, which had to be removed before adding SDL libraries to test executable.

Excellent work. I will have a look over your code as soon as I can (which might not be too soon :( ). I suggest merging this back to trunk now as it is a very important fix. Feel free to do this at any time.

Released in build16-rc1