Re: Sharing a lua_State across DLL boundary

Hi Julien,

not sure if this applies to Windows and DLLs, too, but I had a similar
experience with GCC and shared modules on Linux: classes registered
with Luabind where only valid within that shared library, but caused
segmentation faults if used across shared library boundaries.

The solution was to patch the luabind::type_id class, and compare
using typeid(T).name() instead of typeid(T)::operator=. For GCC, the
reason why the typeid operator might not work across shared libraries
is explained here [1]. In this particular case, I loaded the shared
library with Lua's require(), which, unfortunately, does not pass
RTLD_GLOBAL to dlopen.

[1] http://gcc.gnu.org/faq.html#dso

The typeid equality problem has appeared in other C++ libraries, e.g.
in boost::any[2], with the same fix[3], typeid(T).name() comparison.

[2] https://svn.boost.org/trac/boost/ticket/754
[3] https://svn.boost.org/trac/boost/changeset/56168

Maybe the attached patch helps in the case of DLLs, too.

Peter

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--- include.orig/luabind/typeid.hpp
+++ include/luabind/typeid.hpp
@@ -6,6 +6,7 @@
 # define LUABIND_TYPEID_081227_HPP
 
 # include <boost/operators.hpp>
+# include <cstring>
 # include <typeinfo>
 # include <luabind/detail/primitives.hpp>
 
@@ -33,17 +34,17 @@
 
     bool operator!=(type_id const& other) const
     {
-        return *id != *other.id;
+        return std::strcmp(id->name(), other.id->name()) != 0;
     }
 
     bool operator==(type_id const& other) const
     {
-        return *id == *other.id;
+        return std::strcmp(id->name(), other.id->name()) == 0;
     }
 
     bool operator<(type_id const& other) const
     {
-        return id->before(*other.id);
+        return std::strcmp(id->name(), other.id->name()) < 0;
     }
 
     char const* name() const