How to make a tuple of const references?

Say there are two functions:

void ff( const std::tuple<const int&> ) { }template < typename TT >void gg( const std::tuple<const TT&> ) { }

and calls to these functions:

int xx = 0;ff( std::tie( xx ) ); // passesgg( std::tie( xx ) ); // FAILS !!

GCC 4.7.2 fails to compile the last line and reports an error note like:

note:   template argument deduction/substitution failed:note:   types ‘const TT’ and ‘int’ have incompatible cv-qualifiersnote:   ‘std::tuple<int&>’ is not derived from ‘std::tuple<const TT&>’

The first question is if this fits with the C++11 standard, and if it doesn't, then why?

Furthermore, to overcome this issue one needs to pass a tuple of const references to gg instead of passing a tuple of non-const references (which std::tie makes). This can be done by:

gg( std::tie( std::cref(x) ) );

however, an extra call to std::cref is kind of tedious, so it would be great to have something like ctie which would make a tuple of const references.

The second question is if there is a need to write ctie manually, and if yes, then is this the best way to do it?

template < typename... T >std::tuple<const T&...> ctie( const T&... args ){    return std::tie( args... );}