[Bug c++/34996] New: Base class of explicitly instantiated class doesn't get instantiated

["rbuergel at web dot de" <gcc-bugzilla at gcc dot gnu dot org>]

test.h:

struct Base
{
        virtual int getX() const=0;
};

template <typename ThisType> class Derived1: public Base
{
        protected:
                static const int X;

        public:
                virtual int getX() const{ return X; }
};

template<int id> class Derived2 : public Derived1<Derived2<id> > {};


test.cpp:
#include "test.h"

template<typename U> const int Derived1<U>::X = 0;

template class Derived2<1>;
// template class Derived1<Base, Derived2::StaticImpl<1> >; //that shouldn't be
necessary


main.cpp:
#include "test.h"

int main()
{
        Base& r = *new Derived2< 1 >();
};

g++ main.cpp test.cpp
/tmp/ccyQeFe1.o: In function `Derived1<Derived2<1> >::getX() const':
main.cpp:(.text._ZNK8Derived1I8Derived2ILi1EEE4getXEv[Derived1<Derived2<1>
>::getX() const]+0x4): undefined reference to `Derived1<Derived2<1> >::X'
collect2: ld returned 1 exit status

gcc doesn't to instantiate "Derived1<Base, Derived2::StaticImpl<1> >" - the
Base class of the explicitly instantiated "Derived2<1>"


some curiosities: 
1. outlining getX() into test.cpp makes it work
2. using g++ test.cpp main.cpp (just reversing the order of the files on the
cmd line) works(!), but compiling each file individually and then linking it
breaks.

I can recognise this behaviour with 3.4.6, 4.1.2, 4.2.2 and 4.3 (snapshot from
20080125)


-- 
           Summary: Base class of explicitly instantiated class doesn't get
                    instantiated
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rbuergel at web dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34996