c++/9128: Typeid does not work on polymorphic classes

c++/9128: Typeid does not work on polymorphic classes

[Peter Schmid]

>Number:         9128
>Category:       c++
>Synopsis:       Typeid does not work on polymorphic classes
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          rejects-legal
>Submitter-Id:   net
>Arrival-Date:   Thu Jan 02 05:06:02 PST 2003
>Closed-Date:
>Last-Modified:
>Originator:     Peter Schmid
>Release:        3.4 20021231 (experimental)
>Organization:
LBNL
>Environment:
System: Linux kiste 2.4.18 #10 Thu Dec 26 00:47:26 CET 2002 i686 unknown
Architecture: i686

	
host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: i686-pc-linux-gnu
configured with: 
>Description:
Gcc 3.4 does no longer accept the legal source code t.C. It does
compile if the base class A is not polymorphic, i.e., if the destructor
is not declared as virtual.
>How-To-Repeat:

source code t.C

#include <typeinfo>

struct A {
  virtual ~A() {} 
};

int main() {
   A* a = new A;
   typeid(*a).name(); 
}


Compiling t.C
g++ -v t.C -W -Wall -save-temps
Reading specs from /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.4/specs
Configured with: 
Thread model: posix
gcc version 3.4 20021231 (experimental)
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.4/cc1plus -E -D__GNUG__=3 -quiet -v -D__GNUC__=3 -D__GNUC_MINOR__=4 -D__GNUC_PATCHLEVEL__=0 -D_GNU_SOURCE t.C -W -Wall t.ii
ignoring nonexistent directory "NONE/include"
ignoring nonexistent directory "/usr/local/i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include/c++/3.4
 /usr/local/include/c++/3.4/i686-pc-linux-gnu
 /usr/local/include/c++/3.4/backward
 /usr/local/include
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.4/include
 /usr/include
End of search list.
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.4/cc1plus -fpreprocessed t.ii -quiet -dumpbase t.C -auxbase t -W -Wall -version -o t.s
GNU C++ version 3.4 20021231 (experimental) (i686-pc-linux-gnu)
	compiled by GNU C version 3.4 20021231 (experimental).
t.C: In function `int main()':
t.C:9: error: request for member `std::type_info::name() const' in `
   __cxa_bad_typeid()()', which is of non-class type `const std::type_info&'

Preprocessed source code t.ii

# 1 "t.C"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "t.C"
# 1 "/usr/local/include/c++/3.4/typeinfo" 1 3
# 38 "/usr/local/include/c++/3.4/typeinfo" 3
# 1 "/usr/local/include/c++/3.4/exception" 1 3
# 40 "/usr/local/include/c++/3.4/exception" 3
extern "C++" {

namespace std
{
# 52 "/usr/local/include/c++/3.4/exception" 3
  class exception
  {
  public:
    exception() throw() { }
    virtual ~exception() throw();


    virtual const char* what() const throw();
  };



  class bad_exception : public exception
  {
  public:
    bad_exception() throw() { }


    virtual ~bad_exception() throw();
  };


  typedef void (*terminate_handler) ();

  typedef void (*unexpected_handler) ();


  terminate_handler set_terminate(terminate_handler) throw();


  void terminate() __attribute__ ((__noreturn__));


  unexpected_handler set_unexpected(unexpected_handler) throw();


  void unexpected() __attribute__ ((__noreturn__));
# 100 "/usr/local/include/c++/3.4/exception" 3
  bool uncaught_exception() throw();
}

namespace __gnu_cxx
{
# 115 "/usr/local/include/c++/3.4/exception" 3
  void __verbose_terminate_handler ();
}

}
# 39 "/usr/local/include/c++/3.4/typeinfo" 2 3

extern "C++" {

namespace __cxxabiv1
{
  class __class_type_info;
}
# 55 "/usr/local/include/c++/3.4/typeinfo" 3
namespace std
{






  class type_info
  {
  public:




    virtual ~type_info();

  private:

    type_info& operator=(const type_info&);
    type_info(const type_info&);

  protected:
    const char *__name;

  protected:
    explicit type_info(const char *__n): __name(__n) { }

  public:



    const char* name() const
    { return __name; }
# 101 "/usr/local/include/c++/3.4/typeinfo" 3
    bool before(const type_info& __arg) const
    { return __name < __arg.__name; }
    bool operator==(const type_info& __arg) const
    { return __name == __arg.__name; }

    bool operator!=(const type_info& __arg) const
    { return !operator==(__arg); }


  public:

    virtual bool __is_pointer_p() const;

    virtual bool __is_function_p() const;







    virtual bool __do_catch(const type_info *__thr_type, void **__thr_obj,
                            unsigned __outer) const;


    virtual bool __do_upcast(const __cxxabiv1::__class_type_info *__target,
                             void **__obj_ptr) const;
  };






  class bad_cast : public exception
  {
  public:
    bad_cast() throw() { }


    virtual ~bad_cast() throw();
  };


  class bad_typeid : public exception
  {
  public:
    bad_typeid () throw() { }


    virtual ~bad_typeid() throw();
  };
}

}
# 2 "t.C" 2

struct A {
  virtual ~A() {}
};

int main() {
   A* a = new A;
   typeid(*a).name();
}

>Fix:
	
>Release-Note:
>Audit-Trail:
>Unformatted: