[Bug c++/36982] Unfolding of template function (in namespace) using overloads (in same namespace) requires forward declarations

["bangerth at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from bangerth at gmail dot com  2009-04-02 22:05 -------

Andrew is right:

>   static inline bool Read( const char* Str, int& v )
>     { v = 0; return true; }
> 
>   template< class T >
>   static inline bool Read( const char* Str, std::vector< T >& v )
>   {
>     T Help;
>     if ( !Read( Str, Help ) )

Upon seeing the template, the compiler determines the set of possible
overloads for the call to Read() -- which consists of the function we're
in right now as well as Read(const char*,int&). Upon instantiation with
T=MyType, it adds to this list the set of functions named Read from the
namespace in which MyType was declared -- i.e. the global namespace, in which
no such function is found. So the overload set remains what it was. As a
consequence, no overload is found.

The fact that other compilers, including earlier versions of gcc, get this
wrong is immaterial.

W.

>       return false;
>     v.push_back( Help );
>     return true;
>   }
> }
> 
> struct MyType
> {
>   int i;
> };
> 
> namespace ReadSpace // Extend the namespace ...
> {
>   static inline bool Read( const char* Str, MyType& v )
>     { return Read( Str, v.i ); }
> }
> 
> using namespace ReadSpace;
> 
> int main()
> {
>   std::vector< MyType > v;
>   const char* Str = "25";
>   return Read( Str, v ) ? 0 : 1;
> }
> 


-- 

bangerth at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36982