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Groups > comp.lang.c++ > #6422
| From | Victor Bazarov <v.bazarov@comcast.invalid> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: ambiguous operator on Visual Studio 2010 |
| Date | 2011-06-08 09:26 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <isnta6$9da$1@dont-email.me> (permalink) |
| References | <959al7FrddU1@mid.individual.net> |
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.
> Is there a workaround other than defining a function 'bool
> superset(flags,flags)' instead of operator >= ?
I can't think of any right now.
V
--
I do not respond to top-posted replies, please don't ask
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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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