code using dynamic_cast causes segfaults when -fno-rtti is used

[Matthias Klose <doko@net.local>]

>Submitter-Id:	net
>Originator:	Sean 'Shaleh' Perry <shalehperry@attbi.com>
>Organization:	The Debian Project
>Confidential:	no
>Synopsis:
>Severity:	serious
>Priority:	medium
>Category:	c++
>Class:		sw-bug
>Release:	3.3 (Debian) (Debian testing/unstable)
>Environment:
System: Debian GNU/Linux (unstable)
Architecture: i686
>Description:
 [ Reported to the Debian BTS as report #188943.
   Please CC 188943@bugs.debian.org on replies.
   Log of report can be found at http://bugs.debian.org/188943 ]
	

3.2.3 / 3.3

Now obviously, dynamic_cast requires rtti so using -fno-rtti is silly.
I ran into this on a C++ project where we had been using -fno-rtti because rtti
was not used.  A recent commit added dynamic_cast code and started segfaulting.
It was believed that the dynamic_cast was at fault and this caused some finger
pointing.  Then the no-rtti was noticed.

The compiler should give a warning (or perhaps even an error) if code requiring
rtti is used while the -fno-rtti option is in effect.

#include <iostream>

class EventHandler {
public:
  virtual ~EventHandler(void) {}

  virtual void thisEvent(void) {}
  virtual void thatEvent(void) {}
};

class MyMenu: public EventHandler {
public:
  virtual void thisEvent(void) { std::cout << "this Menu handler\n"; }
  virtual void thatEvent(void) { std::cout << "that Menu handler\n"; }
};

class OtherThing: public EventHandler {
public:
  virtual void thisEvent(void) { std::cout << "this OtherThing handler\n"; }
  virtual void thatEvent(void) { std::cout << "that OtherThing handler\n"; }
};

void do_event(EventHandler* handler) {
  if (dynamic_cast<MyMenu*>(handler)) {
    // also call thatHandler for menus
    handler->thatEvent();
  }

  handler->thisEvent();
}

int main(int argc, char* argv[]) {
  MyMenu menu;
  OtherThing thing;

  do_event(&menu);

  do_event(&thing);

  exit(0);
}

>How-To-Repeat:
	
>Fix: