Undefined reference to static member in templated class

Undefined reference to static member in templated class

[Arun Saini]

hi all,

I am using gcc-2.95.3 on AIX 4.3.3 / RS/6000. I am enclosing here a small
piece of code that compiled and executed correctly on gcc-3.0 on a Linux
system. It however fails on the AIX system.

#include<cstdio>
 enum eTables
   {
      tbl1,
      tbl2
   };

template <class a, eTables e> class test
   {
      private:
      static test<a, e> * foo;
      protected:
      public:
         test();
         virtual ~test();
         static test<a, e> *Instance();
   };  //class test

      template <class a,  eTables e>
      test<a, e>
      *test<a, e>::foo = NULL;

   template <class a,  eTables e>
      test<a, e>::test()
   {
   }

   template <class a,  eTables e>
      test<a, e>::~test()
   {
   }

   template <class a,  eTables e>
      test<a,e>
      *test<a, e>::Instance()
   {
      if (foo == NULL)
      {
         foo = new test<a, e>;
      }

      return(foo);
   }


int main()
{
  test<int, tbl1> *pobj;
  pobj = test<int, tbl1>::Instance();
}


# g++ testFinal.cpp
/tmp/cc8zh32c.o(.pr+0x13e):testFinal.cpp: undefined reference to `test<int,0>::foo'
/tmp/cc8zh32c.o(.pr+0x14e):testFinal.cpp: undefined reference to `test<int,0>::foo'
/tmp/cc8zh32c.o(.pr+0x21a):testFinal.cpp: undefined reference to `test<int,0>::foo'
/tmp/cc8zh32c.o(.tc+0x0):testFinal.cpp: undefined reference to `test<int,0>::foo'
collect2: ld returned 1 exit status


Any ideas why this might be happening????

Arun Saini


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Re: Undefined reference to static member in templated class

[David Edelsohn]

>>>>> Arun Saini writes:

Arun> I am using gcc-2.95.3 on AIX 4.3.3 / RS/6000. I am enclosing here a small
Arun> piece of code that compiled and executed correctly on gcc-3.0 on a Linux
Arun> system. It however fails on the AIX system.

	GCC has known problems with templates on AIX because GCC does not
have a very advanced template generation facility and relies on WEAK
symbols to clean up after it.  AIX does not provide WEAK symbols.

	For AIX, one needs to use -fno-implicit-templates option for GCC
and explicitly instantiate the necessary templates in the code.

David