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Re: ambiguous operator on Visual Studio 2010

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"Victor Bazarov" <v.bazarov@comcast.invalid> wrote in message 
news:isnta6$9da$1@dont-email.me...
> On 6/8/2011 9:09 AM, Aaron Gray wrote:
>> I am getting an ambiguous operator error in VS2010 but not in GCC 4.5.
>>
>> The following code illustrates the problem :-
>>
>>
>> enum flags { OK, TEST };
>>
>> inline bool operator >= (flags f1, flags f2) {
>> return (f1 & f2) == f2;
>> }
>>
>> int main(int argc, char *argv[]) {
>> flags f1 = OK;
>> flags f2 = TEST;
>> bool b = f1 >= f2;
>> return 0;
>> }
>>
>>
>> gives the following on VS2010 :-
>>
>> 1> test.cpp
>> 1>c:\test\c++\operator-test\operator-test\test.cpp(10): error C2593:
>> 'operator >=' is ambiguous
>> 1> c:\test\c++\operator-test\operator-test\test.cpp(3): could be 'bool
>> operator >=(flags,flags)'
>> 1> or 'built-in C++ operator>=(flags, flags)'
>> 1> while trying to match the argument list '(flags, flags)'
>>
>> What is the correct ISO C++ 2004 behaviour ?
>
> The correct behavior is to call the user-defined operator.
>
> Seems like a bug in the compiler that can't make the correct choice 
> between a user-defined function with each argument's matching exactly and 
> the built-in operator that requires a conversion (integral promotion).  I 
> say, report it.  Comeau gets it right as well.
>
> I believe the Visual C++ creators missed the fact that in order for the 
> compiler to use >= with enumeration, the integral promotion [conv.prom] 
> should be performed (see [expr.rel]/2), and according to [over.ics.scs]/3 
> an exact match (for identity category) has a higher rank than a promotion. 
> A clear bug.

Right !

>> Is there a workaround other than defining a function 'bool
>> superset(flags,flags)' instead of operator >= ?
>
> I can't think of any right now.

If thats the case I'll use the function workaround.

Many thanks,

Aaron

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Thread

ambiguous operator on Visual Studio 2010 "Aaron Gray" <ang.usenet@gmail.com> - 2011-06-08 14:09 +0100
  Re: ambiguous operator on Visual Studio 2010 Victor Bazarov <v.bazarov@comcast.invalid> - 2011-06-08 09:26 -0400
    Re: ambiguous operator on Visual Studio 2010 "Aaron Gray" <ang.usenet@gmail.com> - 2011-06-08 14:58 +0100
      Re: ambiguous operator on Visual Studio 2010 "Aaron Gray" <ang.usenet@gmail.com> - 2011-06-08 17:22 +0100
        Re: ambiguous operator on Visual Studio 2010 "Balog Pal" <pasa@lib.hu> - 2011-06-08 18:47 +0200
          Re: ambiguous operator on Visual Studio 2010 Krice <paulkp@mbnet.fi> - 2011-06-08 11:40 -0700
          Re: ambiguous operator on Visual Studio 2010 "Bo Persson" <bop@gmb.dk> - 2011-06-08 21:29 +0200
            Re: ambiguous operator on Visual Studio 2010 "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-08 21:50 +0200
              Re: ambiguous operator on Visual Studio 2010 Öö Tiib <ootiib@hot.ee> - 2011-06-08 16:06 -0700
                Re: ambiguous operator on Visual Studio 2010 "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-09 03:20 +0200
                Re: ambiguous operator on Visual Studio 2010 Krice <paulkp@mbnet.fi> - 2011-06-09 03:00 -0700
                Re: ambiguous operator on Visual Studio 2010 "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-09 20:46 +0200
                Re: ambiguous operator on Visual Studio 2010 Krice <paulkp@mbnet.fi> - 2011-06-09 23:08 -0700
                Re: ambiguous operator on Visual Studio 2010 Öö Tiib <ootiib@hot.ee> - 2011-06-10 02:33 -0700
                Re: ambiguous operator on Visual Studio 2010 "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-10 12:26 +0200
                Re: ambiguous operator on Visual Studio 2010 Öö Tiib <ootiib@hot.ee> - 2011-06-09 04:52 -0700
                Re: ambiguous operator on Visual Studio 2010 "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-09 20:51 +0200
                Re: ambiguous operator on Visual Studio 2010 Öö Tiib <ootiib@hot.ee> - 2011-06-10 01:58 -0700
                Re: ambiguous operator on Visual Studio 2010 "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-06-10 12:36 +0200
            Re: ambiguous operator on Visual Studio 2010 "Balog Pal" <pasa@lib.hu> - 2011-06-09 13:32 +0200
          Re: ambiguous operator on Visual Studio 2010 "Balog Pal" <pasa@lib.hu> - 2011-06-10 12:24 +0200

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