losing data when using dynamic_cast to derive object - c++

Question

when I push fifoGroundEvtEntry data inside list_fifoGroundEvt from another thread using sender::GetInstance()->getDataCollector()->pushGroundEventFifo(entry); and when I debug puting one breakpoint inside pushGroundEventFifo function I can see the correct value of grdEvt.x and grdEvt.y inside list_fifoGroundEvt.
then when I call test method inside transmit methode and I pute breakpoint inside test. I see wrong values inside list_fifoGroundEvt-> grdEvt.y = 0x00F12751 for entry.y = 2 !
PS: transmit() is a thread and I start it using sender::GetInstance()->start() (I didn't put all functions I put only those who have a link with the problem )
the thread is starting after pushing entries inside list_fifoGroundEvt
#include "stdafx.h"
#include <iostream>
#include <list>
struct fifoEvtEntry {
virtual ~fifoEvtEntry() {}
int x;
};
struct fifoGroundEvtEntry : fifoEvtEntry
{
int y;
};
class collector {
public:
void pushGroundEventFifo(fifoEvtEntry& entry) {
if (fifoGroundEvtEntry* grdEvt = dynamic_cast<fifoGroundEvtEntry*>(&entry))
{
list_fifoGroundEvt.push_back(grdEvt);
}
}
void test() {
if (fifoGroundEvtEntry* grdEvt = dynamic_cast<fifoGroundEvtEntry*>(list_fifoGroundEvt.front()))
{
std::cout << grdEvt ->y << std::endl;
}
list_fifoGroundEvt.pop_front();
}
private:
std::list<fifoEvtEntry*> list_fifoGroundEvt;
};
class sender {
public:
sender(collector* data):_data(data) {};
~sender() {};
static void setInstance(collector* data) {
_instance = new sender(data);
}
static sender* GetInstance() {
return _instance;
}
void transmit() {
// this is a thread function
// ..
_data->test();
}
collector* getDataCollector(){
return _data;
}
static sender* _instance;
private:
collector* _data;
};
int main(){
return 0;
}