No hash function for enums in Boost 1.51

[Steven Barbaglia <steven.barbaglia@…>]

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<> &)'

[Daniel James]

Thanks for the bug report. This was fixed in [80292], which will be included in 1.52.

[Steven Barbaglia <steven.barbaglia@…>]

Full error report from MSVC 2010

[Steven Barbaglia <steven.barbaglia@…>]

Great news! Thank you.