The following simple program doesn't link:

----- Derived.h -----
#ifndef Derived_hh
#define Derived_hh

#include <istream>
#include <ostream>

class D : public std::iostream
{
public:
    ~D() ;
} ;
#endif
----- Derived.cc -----
#include "Derived.hh"

D::~D()
{
}
----- main.cc -----
#include "Derived.hh"

int
main()
{
    D d ;
    return 0 ;
}
----- -----
The compiler command was simply "g++ main.cc Derived.cc".

Output was:
----- compiler output -----
/home/kanze/tmp/ccJrgTHi.o(.gnu.linkonce.t._ZN1DC1Ev+0x29): In function `D::D()':
: undefined reference to `std::basic_iostream<char, std::char_traits<char>
>::basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.text+0x149): In function `D::~D()':
: undefined reference to `std::basic_iostream<char, std::char_traits<char>
>::~basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.text+0x1fa): In function `D::~D()':
: undefined reference to `std::basic_iostream<char, std::char_traits<char>
>::~basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.text+0x2ac): In function `D::~D()':
: undefined reference to `std::basic_iostream<char, std::char_traits<char>
>::~basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.gnu.linkonce.r._ZTC1D0_Sd+0xc): undefined reference
to `std::basic_iostream<char, std::char_traits<char> >::~basic_iostream()'
/home/kanze/tmp/cctV9drU.o(.gnu.linkonce.r._ZTC1D0_Sd+0x10): undefined reference
to `std::basic_iostream<char, std::char_traits<char> >::~basic_iostream()'
collect2: ld returned 1 exit status
----- -----
I'm not an expert in your template instantiation strategy, but
when I compile Derived.cc separately, then use nm on the object
file, I find unresolved externals for symbols like std::iostream::~iostream
(which shouldn't exist except as a typedef to a template instantiation,
I think).  From what little I understand, I would have expected a
weak definition for the template instantiation (the missing function
in the messages above).

The relevant options I used when building the compiler were:
    --enable-threads --enable-__cxa_atexit --disable-nls
(I don't think they have anything to do with the problem, but one
never knows.)

--
James Kanze