[boost] Re: Very odd Comeau C++ behavior

From: Comeau Computing (comeau_at_[hidden])
Date: 2004-02-26 10:47:58

Just a follow up that in addition to the work around previously sent below, 
there is now a patch that fixes the underlying problem.   Holler if you 
need a revised compiler.

- Greg

At 08:40 PM 1/26/2004 +0200, Peter Dimov wrote:
>While implementing operator== for boost::mem_fn, I found that the following
>program, which I expected to print '1' six times, mysteriously outputs 1 0 1
>1 0 1 under Comeau C++, causing all mem_fn equality tests to fail:
>
>#include <iostream>
>
>struct X
>{
>     int mf0_1() { return 0; }
>     int mf0_2() { return 0; }
>};
>
>struct mf0
>{
>     typedef int (X::*F) ();
>     F f_;
>
>     explicit mf0(F f): f_(f) {}
>
>     bool operator==(mf0 const & rhs) const
>     {
>         return f_ == rhs.f_;

Thanks for the report, it appears you've uncovered a problem.   It's being 
looked into further.   For now, this should work:

            return f_ == rhs.f_ ? true : false;

>     }
>
>     bool operator!=(mf0 const & rhs) const
>     {
>         return f_ != rhs.f_;

As well as here:

            return f_ != rhs.f_ ? true : false;

>     }
>};
>
>int main()
>{
>     std::cout << ( &X::mf0_1 == &X::mf0_1 ) << std::endl;
>     std::cout << ( mf0(&X::mf0_1) == mf0(&X::mf0_1) ) << std::endl;
>     std::cout << ( mf0(&X::mf0_1).f_ == mf0(&X::mf0_1).f_ ) << std::endl;
>
>     std::cout << "--\n";
>
>     std::cout << ( &X::mf0_1 != &X::mf0_2 ) << std::endl;
>     std::cout << ( mf0(&X::mf0_1) != mf0(&X::mf0_2) ) << std::endl;
>     std::cout << ( mf0(&X::mf0_1).f_ != mf0(&X::mf0_2).f_ ) << std::endl;
>}
>
>Output:
>
>C:\Documents and Settings\pdimov\My Documents\Projects\testbed>como
>testbed.cpp
>Comeau C/C++ 4.3.0.1 (Aug 21 2002 15:45:32) for MS_WINDOWS_x86
>Copyright 1988-2002 Comeau Computing.  All rights reserved.
>MODE:strict errors C++
>
>
>C:\Documents and Settings\pdimov\My Documents\Projects\testbed>aout.exe
>1
>0
>1
>--
>1
>0
>1
>
>Is this a known issue with Comeau C++ 4.3? Or is there something wrong with
>the code?

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