Here is the test example that causes the problem. I tried to reduce it to its
strict minimum:

test.cpp:

#include <string>

class A  {
  std::string mesg;
};

class B : public virtual A {};

template <class Type> class C : public B {};

int main() {
  C<int> j;
}

By compiling it with g++ 3.3.1 (Mandrake 9.2):
   g++ -O1 -o test test.cpp

Returns error:

/tmp/ccwnGZD1.o(.text+0x23): In function `main':
: undefined reference to `VTT for C<int>'
collect2: ld a retourné 1 code d'état d'exécution

  It seems that it has some problem instanciating the template class C<int>
automatically. Here are different tests that DO work (each test is independant):

   - replace "std::string mesg" by "int mesg"
   - manually instanciate template class by putting
        "template class C<int>;"
      just before the main declaration
   - Move the delaration of j outside of main (global definition)
   - Compile with no optimisation (-O0 for example)

To clarify things I tested this under:
   gcc 3.3.1 by Mandrake 9.2 : Failed
   gcc 3.3.2 by Fedora : Failed
   gcc 3.3.3 home compiled (with no options) : Failed

   gcc 3.2.2 by RedHat 9 : Work

I thus suspect that this problem appeared with gcc versions 3.3 . It may also be
that gcc 3.3 is more strict on the code but I have found no indication to suport
this.

Clement Menier.

-- 
           Summary: Instanciation problem of template class derived from
                    virtual base class
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Clement dot Menier at inrialpes dot fr
                CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i686-px-linux-gnu
GCC target triplet: i686-px-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14865