[Boost-bugs] [Boost C++ Libraries] #7437: No hash function for enums in Boost 1.51

Subject: [Boost-bugs] [Boost C++ Libraries] #7437: No hash function for enums in Boost 1.51
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-09-27 12:12:10

#7437: No hash function for enums in Boost 1.51
--------------------------------------------------------------+-------------
 Reporter:  Steven Barbaglia <steven.barbaglia@…>             |       Owner:  danieljames
     Type:  Bugs                                              |      Status:  new        
Milestone:  To Be Determined                                  |   Component:  hash       
  Version:  Boost 1.52.0                                      |    Severity:  Problem    
 Keywords:                                                    |  
--------------------------------------------------------------+-------------
 Using enums as keys in maps has become problematic in Boost 1.51.  The
 following code compiles with Microsoft Visual C++ 2010 under Boost 1.50,
 but not Boost 1.51:

 {{{
 #include <boost/unordered_map.hpp>

 class MyClass
 {
 public:
     enum eMyEnum
     {
         red,
         white,
         green
     };
 };

 typedef boost::unordered_map<MyClass::eMyEnum,std::string> MyMap;

 int main(int argc, char* argv[])
 {
     MyMap m;
     MyMap::value_type v(MyClass::red,"apples");
     m.insert(v);

     return 0;
 }

 }}}

 An extract from the error report is:
 {{{
 boost\functional\hash\extensions.hpp(257): error C2665:
 'boost::hash_value' : none of the 2 overloads could convert all the
 argument types
 boost\functional\hash\hash.hpp(115): could be 'size_t
 boost::hash_value(std::type_index)'
 boost\functional\hash\extensions.hpp(160): or       'size_t
 boost::hash_value(const std::tr1::tuple<> &)'
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7437>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.