yes I've seen your header there, but that error really looks like a missing header file, so I was wondering whether you had edited your file in order to obtain those errors.
I had a look at
/usr/xenomai/include/trank/native/task.h and it declares
COMPAT_DECL(int, rt_task_spawn(RT_TASK *task, const char *name,
int stksize, int prio, int mode,
void (*entry)(void *arg), void *arg));
not sure what that macro is supposed to do, but I guess you have to get the
-D options right for that to work...
g++ compile line you posted works for me .
This is my configure line:
../../xenomai-3.0.3/configure --disable-debug --with-core=cobalt --enable-pshared --build=arm
Also, it looks like you have cross-compiled the library, I am not sure if that is causing issues?