[Bug libstdc++/25466] New: typeid expression fails to throw bad_typeid according to 5.2.8p2

["hhinnant at apple dot com" <gcc-bugzilla@gcc.gnu.org>]

5.2.8p2 says that if a typeid expression refers to a polymorphic type and the
expression is formed by dereferencing a null pointer that a bad_typeid should
be thrown.

#include <iostream>
#include <typeinfo>

template <class T>
bool is_polymorphic() {
   bool result(false);
   typeid( (result=true), *(T*)0);
   return result;
}

struct non_polymorphic {};
struct polymorphic { virtual ~polymorphic() {} };


int main() {
   std::cout << is_polymorphic<int>() << '\n';
   std::cout << is_polymorphic<non_polymorphic>() << '\n';
   try
   {
      std::cout << is_polymorphic<polymorphic>() << '\n';              //3
      std::cout << "Fail, should have thrown bad_typeid\n";
   }
   catch (std::bad_typeid&)
   {
      std::cout << "Pass\n";
   }
   catch (...)
   {
      std::cout << "Fail, bad_typeid not caught\n";
   }
}

Expected output:

0
0
Pass

Output received with gcc 4.0.1

0
0
1
Fail, should have thrown bad_typeid


-- 
           Summary: typeid expression fails to throw bad_typeid according to
                    5.2.8p2
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hhinnant at apple dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25466