[Bug c++/31074] New: Reference casting involving multiple inheritance produces bad pointer

[hagin at us dot ibm dot com]

When casting a const reference of a derived class (which inherits from multiple
classes with virtual methods) to a non-const reference of one of it's base
classes, the resulting non-const base class reference points to an incorrect
address. 

system type/gcc build options/version:

Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/u
sr/share/info --enable-shared --enable-threads=posix --enable-checking=release
-
-with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions
--with-gx
x-include-dir=/usr/include/c++/3.4.3 --enable-libgcj-multifile
--enable-language
s=c,c++,java,f95 --enable-java-awt=gtk --disable-dssi
--with-java-home=/usr/lib/
jvm/java-1.4.2-gcj-1.4.2.0/jre --with-cpu=generic --host=x86_64-redhat-linux
Thread model: posix
gcc version 4.1.0 20060515 (Red Hat 4.1.0-18)

command line: 

compile code with command /usr/bin/g++4 cast.cpp
execute a.out

compiler output:  

no compiler messages
execution of program results in "Segmentation fault"

preprocessed file:

# 1 "cast.cpp"
# 1 "/home/hagin//"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "cast.cpp"
class Shape
{
public:
  Shape() {}
  virtual ~Shape() {}
};

class Loop
{
public:
  Loop() {}
  virtual ~Loop() {}
  virtual void func() {}
};

class Rect :
  public Shape,
  public Loop
{
public:
  Rect() {}
  virtual ~Rect() {}
};

int main ()
{
  const Rect* rect = new Rect();
  ((Loop&)(*rect)).func();
  return 0;
}


-- 
           Summary: Reference casting involving multiple inheritance
                    produces bad pointer
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hagin at us dot ibm dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31074