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Date: Tue, 18 May 2010 03:37:00 -0000
Subject: [Bug c++/44186]  New: Wrong code generated with -O2 and above
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From: "eyakubovich at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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This is a stripped down code from proposed Boost.Move library. Asserts don't
fire with -O0 and -O1 but do with -O2 and -O3

#include <assert.h>

template <class T>
class rv : public T
{
   rv();
   ~rv();
   rv(rv const&);
   void operator=(rv const&);
};

template <class T>
rv<T>& move(T& x)
{
   return *static_cast<rv<T>* >(&x);
}

//A movable class
class movable
{
   movable(movable &);
   movable& operator=(movable&);
public:
   operator rv<movable>&()
   {  return *reinterpret_cast< rv<movable>* >(this);  }
   operator const rv<movable>&() const
   {  return *reinterpret_cast<const rv<movable>* >(this);  }

private:
   int value_;

public:
   movable() : value_(1){}

   //Move constructor and assignment
   movable(rv<movable>& m)
   {  value_ = m.value_;   m.value_ = 0;  }

   movable & operator=(rv<movable>& m)
   {  value_ = m.value_;   m.value_ = 0;  return *this;  }

   bool moved() const //Observer
   {  return value_ == 0; }
};

movable function(movable m)
{
   return movable(move(m));
}

int main()
{
   {
      movable m;
      movable m2(move(m));
      assert(m.moved());
      assert(!m2.moved());
   }

   {
      movable m;
      movable m3(function(movable(move(m))));
      assert(m.moved());
      assert(!m3.moved());
   }

   {
      movable m;
      movable m4(function(move(m)));
      assert(m.moved());
      assert(!m4.moved());
   }

   return 0;
}


-- 
           Summary: Wrong code generated with -O2 and above
           Product: gcc
           Version: 4.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: eyakubovich at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44186