problem of template inheritance on g++

Digvijoy Chatterjee chatterjee.digvijoy@gmail.com
Wed May 10 08:10:00 GMT 2006


On 5/10/06, amol <gajewar.amol@spsoftindia.com> wrote:
> Following is the code which works on windows but can't work with g++
>
>
> template < class  my_type>
>
> class mytypedef
>  {
>             public :
>                         typedef my_type  new_type;
> };
>
>
>
> template <class my_type>
>
> class sample: public mytypedef < my_type >
>
> {
>
>             public :
>
>                         new_type var;
>
> };
>
>
>
> Error : new_type doest not name a type.
>
>
>
> Why is it happening?
>
> What is solution for this problem?
>
>
>
> Amol Gajewar
Solution ,as suggested by g++(4.0.2) itself works
myshec-linux:~ # g++ -c temp.cpp
error: 'new_type' does not name a type
note: (perhaps 'typename mytypedef<my_type>::new_type' was intended)

when i used what g++ suggested (the part which follows note :it worked )

what i think is :
first compiler will not look for definition of new_type in the base
class scope ,there was a similar thread today which pointed to this
URL
http://gcc.gnu.org/ml/gcc-help/2004-04/msg00382.html
second , the typename keyword is needed ,otherwise the compiler will
not believe that
new_type is a type , it will assume it as a static member or a enum or
an object ,but it wont-cannot know that it is a type , until the
template is instantiated...so u have to use typename.
VC++ rules might be different , but this is the standard.

HTH
Digz



More information about the Gcc-help mailing list