rework lua-bridge C++ variable references

Since lua functions are closures, C++ methods that pass arguments by
reference cannot be used directly. The previous approach (boost::ref)
failed with clang. Assume the following:

  void foo (float&) { }
  static inline float& bar () {
    boost::reference_wrapper<float> r (42);
    return r.get ();
  }

  foo ( bar () );

With gcc, "r" goes out of scope after foo's arguments are processed
and all is well.
But with clang,  "r" already leave scope when *inlined* bar() returns.

Solution: allocate some user-data on the lua-stack to hold the reference.
There is no reference to this user-data so lua will eventually
garbage collect it.

(theoretically, creating the table which holds the return-values
could trigger an emergency garbage collection when memory is low and
free the reference just while they're being pushed to the table, then
gain FuncArgs<Params> already dereferenced them all as variable on the
C stack -- probably again compiler specific)

1 files changed, 0 insertions, 1 deletions

diff --git a/libs/lua/LuaBridge/LuaBridge.h b/libs/lua/LuaBridge/LuaBridge.h
index 706e77cbfd..01f9e90b7d 100644
--- a/libs/lua/LuaBridge/LuaBridge.h
+++ b/libs/lua/LuaBridge/LuaBridge.h
@@ -47,7 +47,6 @@
 #include <vector>
 
 #include <inttypes.h>
-#include <boost/ref.hpp>
 #include <boost/type_traits.hpp>
 #include <boost/shared_ptr.hpp>