Compiler bug: error C2839 when operator-> returns pointer to built-in type

From:

"Niels Dekker - no return address" <unknown@this.is.invalid>

Newsgroups:

microsoft.public.vc.language

Date:

Mon, 28 May 2007 12:36:52 +0200

Message-ID:

<u6DPRQRoHHA.596@TK2MSFTNGP06.phx.gbl>

When operator->() returns a pointer to a built-in type (e.g., char), it
doesn't work properly on either VC++ 2003 or VC++ 2005. The following
valid C++ program is rejected by VC++, saying:
  error C2839: invalid return type 'C *' for overloaded 'operator ->'

  //////////////////////////////////////////////////////////////////////
  typedef char C;

  template <typename T>
  class SmartPointer {
    T * m_ptr;
  public:
    T * operator->() const {
      return m_ptr;
    }
    SmartPointer(T* arg) : m_ptr(arg) {
    }
  };

  int main() {
    C* rawPtr = 0;
    SmartPointer<C> smartPtr = 0;

    rawPtr->~C(); // Okay :-)
    smartPtr.operator->()->~C(); // Okay :-)
    smartPtr->~C(); // error C2839!!! :-(
  }
  //////////////////////////////////////////////////////////////////////

Is this a known bug? I didn't find it at
https://connect.microsoft.com/VisualStudio/feedback

FYI, the thing is relevant to the resolution of C++ Standard Library
issue 659, "istreambuf_iterator should have an operator->()"
http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-active.html#659

Kind regards,
--
Niels Dekker
http://www.xs4all.nl/~nd/dekkerware
Scientific programmer at LKEB, Leiden University Medical Center