Adding symbols from libge_*.a into blender's dynamic tables

[Liebranca]

Hi,

From the ld manual:

If you use dlopen to load a dynamic object which needs to refer back to the symbols defined by the program, rather than some other dynamic object, then you will probably need to use this option when linking the program itself.

The linker flag in question being --export-dynamic. With this, an extension could load symbols directly from blender, which I would appreciate.

Far as I can tell, this is switched off. Tried:

nm --demangle --dynamic ~/blender-git/build_linux/bin/blender | grep "KX_GameObject::"

Which returns nothing. Running the same command on libge_ketsji.a I get a more informative answer: no dynamic symbols on any of the object files within the lib.

So: here I am, asking questions.

1. where do linker flags go?
2. is -fvisibility=hidden switched on somewhere?

Reason why I want to do this:

#include <iostream>
#include "KX_GameObject.h"

extern "C" void test(KX_GameObject* own) {
  KX_GameObject cpy=*own;
};

Linked as a shared object; loaded with ctypes at game startup, passed cont.owner as a ctypes.py_object, which AFAIK should correspond to PyObject*.

Running this test should attempt a vtable lookup, then segfault because I most likely passed it a bogus pointer. But instead it throws OSError as soon as I init my lib:

bcpp-test.so: undefined symbol: _ZTV13KX_GameObject

And oh, that's too bad. But what does the binary say?

nm ~/blender-git/build_linux/bin/blender | grep "_ZTV13KX_GameObject"
0000000004ba5950 d _ZTV13KX_GameObject

Found. Let's demangle:

nm --demangle ~/blender-git/build_linux/bin/blender | grep "0000000004ba5950"
0000000004ba5950 d vtable for KX_GameObject

Looks to me me like Blender knows where the vtable is, it just doesn't want to share ;>

But as I see it, sharing is good. I don't even need every last symbol to be accessible to extensions, just the game engine ones for starters.

What do you guys think? Is this viable?

[youle31]

I don't understand anything sorry. It sounds very technical. I convert this to discussion as we are trying to keep this place for most important bugs only. Thanks for comprehension.

[Liebranca]

Oops! my bad.

Gist of it is I need to make a change in the build process to enable dll and so files to lookup functions within a running instance of blender or blenderplayer; that way compiled extensions wouldn't need to include them.

But this is for a C++ API so I don't think blenderdevs would tell me ;> Guess I'll have to try adding linker switches to game engine CMakeLists and see what happens.