gcc - Dynamic Cast C++ Fail -

i having dynamic cast fail on g++ compiler (redhat 5.5 gcc version 3.4.6) works fine on windows visual studio 2003, 2005, , 2010 compiler. understand seeing try break problem down. have process loads in numerous "plugins" directory , dynamically loads these plugins (which dynamically linked libraries). process supposed compare different rules , data types return answer. make process modulure made process understand "basedatatype" not actual specific types (so keep process generic). flow of program goes this:

all our "specifcobject" types inherit "basedatatype" this

class specificobject : public virtual basedatatype {     ... class items ... } 

this code process looks like:

// receive raw data  void receive_data(void *buff, int size,datatypeenum type) {    // plugin associated data    processplugin *plugin = m_plugins[type];     // since need cast data actual type , not    // base data type need plugin cast (so can keep     // process generic)    basedatatype *data = plugin->getdataobject(buff);    if(data)    {      // cast worked fine       .... other things happen (but object isn't modified) ....      // compare our rule      ruleobject obj = getrule();      resultobject *result = plugin->comparedata(obj,data);      if(result)         ... success case ...      else         ... error case ...    }  } 

now (generically) plugin like

basedatatype* processpluginone::getdataobject(unsigned char *buff) {     // specificobject inherits basedatatype using "virtual" inheritance     specificobject *obj = reinterpret_cast<specificobject*>(buff);     if(obj)        return (basedatatype*)obj;     else        return null; }  resultobject* processpluginone::comparedata(ruleobject rule, basedatatype *data) {    resultobject *obj = null;    // method checks out fine    if(data->getsomebasemethod())    {       // cast below fails every time in gcc passes in visual studio       specificobject *obj = dynamic_cast<specificobject*>(data);       if(obj)       {             ... ...       }    }     return result; } 

again of works under visual studio not under gcc. debug program started adding code different sections. got work once did following in main process (see added code below):

// in process modification void receive_data(void *buff, int size,datatypeenum type) {    // plugin associated data    processplugin *plugin = m_plugins[type];     // since need cast data actual type , not    // base data type need plugin cast (so can keep     // process generic)    basedatatype *data = plugin->getdataobject(buff);    if(data)    {      // cast worked fine       .... other things happen (but object isn't modified) ....      // compare our rule      ruleobject obj = getrule();       /** included specific data types in headers debugging , linked in        * specific classes , added following code       */      specificobject *test_obj = dynamic_cast<specificobject*>(data);      if(test_obj)         cout << "our data casted correctly!" << endl;      /// code above fixes bad cast in plugin though       /// code above        resultobject *result = plugin->comparedata(obj,data);      if(result)         ... success case ...      else         ... error case ...    }  } 

significant process compile options:

compile: -m64 -fpic -wno-non-template-friend -dndegbug -i <includes> link: -wl -z muldefs -m64 

significant plugin compile options

compile: -wall -wno-non-template-friend -o -o2 link: -wl -bstatic -bdynamic -z muldefs -shared -m64 

since not modifying object "data" have no idea why rest of program start working. thing can think of virtual table getting stripped off somewhere in process , "extra" dynamic cast forces main process keep table (which still doesn't make lot of sense).

i have tried taking out optimization settings in gcc , still same. thoughts going on here?

thanks.

the 2 scenarios basedatatype not polymorphic type, or compiler doesn't see relationship between basedatatype , specificobject @ point in code (for example, in getdataobject compiler might generate different code depending on knowledge of parent-child relationship, since use c-cast child parent. super easy check: change c-cast static_cast. if fails compile you're missing critical include.