optimization/5006

[Richard Smith]

Sorry, the test case seemed to get lost somewhere on route.  It ought to
be attached to this.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail%26pr=5006%26database=gcc

--
Richard Smith
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// doesn't matter whether this is define'd to throw() or to left blank
#define __STL_NOTHROW 

// ---- extract from <memory> header ----

template<class _Tp1> struct auto_ptr_ref 
{
  _Tp1* _M_ptr;
  auto_ptr_ref(_Tp1* __p) : _M_ptr(__p) {}
};

template <class _Tp> class auto_ptr {
private:
  _Tp* _M_ptr;

public:
  typedef _Tp element_type;

  explicit auto_ptr(_Tp* __p = 0) __STL_NOTHROW : _M_ptr(__p) {}

  auto_ptr(auto_ptr& __a) __STL_NOTHROW : _M_ptr(__a.release()) {}

  template <class _Tp1> auto_ptr(auto_ptr<_Tp1>& __a) __STL_NOTHROW
    : _M_ptr(__a.release()) {}

  auto_ptr& operator=(auto_ptr& __a) __STL_NOTHROW 
  {
    reset(__a.release());
    return *this;
  }

  template <class _Tp1>
  auto_ptr& operator=(auto_ptr<_Tp1>& __a) __STL_NOTHROW 
  {
    reset(__a.release());
    return *this;
  }
  
  // Note: The C++ standard says there is supposed to be an empty throw
  // specification here, but omitting it is standard conforming.  Its 
  // presence can be detected only if _Tp::~_Tp() throws, but (17.4.3.6/2)
  // this is prohibited.
  ~auto_ptr() 
  {
    delete _M_ptr; 
  }
 
  _Tp& operator*() const __STL_NOTHROW {
    return *_M_ptr;
  }
  _Tp* operator->() const __STL_NOTHROW {
    return _M_ptr;
  }
  _Tp* get() const __STL_NOTHROW {
    return _M_ptr;
  }
  _Tp* release() __STL_NOTHROW {
    _Tp* __tmp = _M_ptr; 
    _M_ptr = 0;
    return __tmp;
  }
  void reset(_Tp* __p = 0) __STL_NOTHROW {
    if (__p != _M_ptr) {
      delete _M_ptr;
      _M_ptr = __p;
    }    
  }

  // According to the C++ standard, these conversions are required.  Most
  // present-day compilers, however, do not enforce that requirement---and, 
  // in fact, most present-day compilers do not support the language 
  // features that these conversions rely on.
public:
  auto_ptr(auto_ptr_ref<_Tp> __ref) __STL_NOTHROW
    : _M_ptr(__ref._M_ptr) {}

  auto_ptr& operator=(auto_ptr_ref<_Tp> __ref) __STL_NOTHROW 
  {
    if (__ref._M_ptr != this->get()) 
      {
	delete _M_ptr;
	_M_ptr = __ref._M_ptr;
      }
    return *this;
  }

  template <class _Tp1> operator auto_ptr_ref<_Tp1>() __STL_NOTHROW 
    { return auto_ptr_ref<_Tp>(this->release()); }

  template <class _Tp1> operator auto_ptr<_Tp1>() __STL_NOTHROW
    { return auto_ptr<_Tp1>(this->release()); }
};

// ---- random stuff to make cause bug ----

class A 
{
public:
  A(void) : ptr(0) { }
  A(const char *p) : ptr(p) { }
  A(const A &other) : ptr(other.ptr) { }
  A &operator=(const A &other) { ptr=other.ptr; }
  ~A() { }
  explicit A(const A *, const A *) { }
private:
  const char *ptr;
};


typedef auto_ptr<A> handle; // for readability

inline handle fish(const A &v) 
{ 
  handle h(new A(v)); 
  return h ;
}

inline handle soup(handle a, handle b)
{ 
  return handle(new A(a.release(), b.release())); 
}

int main()
{
  // This seems to need to be this complicated.  Every simplification
  // that I've tried stops the bug from occuring.
  soup(soup(handle(), fish(A("foo"))), fish(A("foo")));
  return 0;
}