Segfault in .so file.

Hello. I'm trying to implement a plugin system and I have this code:

//myplugin.cpp
#include "Plugin.hpp"

namespace mp {

class MyPlugin : public Plugin { ...}
}

REGISTER_PLUGIN("MyPlugin", MyPlugin, mp);

//Plugin.hpp
class PluginsManager : public Singleton<PluginsManager>
{
private:
      map<string, function<shared_ptr<Plugin> > factory_;

public:
    bool registerPlugin(const string id, function<shared_ptr<Plugin> >
factoryfunc)
    {
        //Segfaults because of this (I think)
        factory_[id] = factoryfunc;
        return true;
    }
}

#define REGISTER_PLUGIN(id, plugtype, ns) shared_ptr<Plugin>
create##ns##plugtype { return\
shared_ptr<Plugin>(new plugtype); }\
const static bool registered##ns##plugtype =
PluginsManager()::instance().registerPlugin(id,\
&create##ns##plugtype)

int main() {
   //OK, Loads the .so file associated with myplugin and the code from
REGISTER_PLUGIN is inmediatly
   //executed. When the code is executed, it segfaults.
   PluginsManager::instance().init();
}

My plugin system inits the PluginsManager, which uses a singleton
which can be used as a shared library.
I think the segfault takes place when accessing factory_[id] =
factoryfunc.
If I put these statements (which are nonsense):

factory_[id];
factoryfunc;

in registerPlugin, it does not segfault. I used the debugger and the
segfault takes place inside an atomic operation
coded in assembly for shared_ptr, I think. Anyone can help how to
avoid this segfault. The boost version is 1.35, and the compiler, the
one who comes with Ubuntu 8.04 (I think it is gcc 4.2.1). Thanks for
your time.

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