Template Method Specialization Trouble in G++ 3.0

[Jim Peterson <jspeter at jimsara dot org>]

To whom it may concern:

  I've appended a bug report below for g++ version 3.0.  Please, let me
know
  how to fix or work around this problem (avoiding 'abstract method' errors
  via a template parameter).

Thank you for your time,
--Jim

==============================================================================

Typing g++ -v -o t.o t.cc -save-temps produces the messages given below:

==============================================================================

Reading specs from /usr/lib/gcc-lib/i686-pc-linux-gnu/3.0/specs
Configured with: ../gcc-3.0/configure --prefix=/usr
Thread model: single
gcc version 3.0
 /usr/lib/gcc-lib/i686-pc-linux-gnu/3.0/cpp0 -lang-c++ -D__GNUG__=3
-D__GXX_DEPRECATED -D__EXCEPTIONS -D__GXX_ABI_VERSION=100 -v -D__GNUC__=3
-D__GNUC_MINOR__=0 -D__GNUC_PATCHLEVEL__=0 -D__ELF__ -Dunix -Dlinux
-D__ELF__ -D__unix__ -D__linux__ -D__unix -D__linux -Asystem=posix
-D__NO_INLINE__ -D__STDC_HOSTED__=1 -D_GNU_SOURCE -Acpu=i386 -Amachine=i386
-Di386 -D__i386 -D__i386__ -D__tune_i686__ -D__tune_pentiumpro__ t.cc t.ii
GNU CPP version 3.0 (cpplib) (i386 Linux/ELF)
ignoring duplicate directory "/usr/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/g++-v3
 /usr/include/g++-v3/i686-pc-linux-gnu
 /usr/include/g++-v3/backward
 /usr/include
 /usr/lib/gcc-lib/i686-pc-linux-gnu/3.0/include
 /usr/i686-pc-linux-gnu/include
End of search list.
 /usr/lib/gcc-lib/i686-pc-linux-gnu/3.0/cc1plus -fpreprocessed t.ii -quiet
-dumpbase t.cc -version -o t.s
GNU CPP version 3.0 (cpplib) (i386 Linux/ELF)
GNU C++ version 3.0 (i686-pc-linux-gnu)
	compiled by GNU C version 3.0.
t.cc:42: no `T* B<T, true>::newT()' member function declared in class `B<T,

   true>'
t.cc:42: template definition of non-template `T* B<T, true>::newT()'
t.cc:45: no `T* B<T, false>::newT()' member function declared in class
`B<T, 
   false>'
t.cc:45: template definition of non-template `T* B<T, false>::newT()'
t.cc: In member function `T* A<T, ClassIsAbstract>::newT() [with T = C,
bool 
   ClassIsAbstract = true]':
t.cc:52:   instantiated from here
t.cc:26: cannot allocate an object of type `C'
t.cc:26:   because the following virtual functions are abstract:
t.cc:30: 	virtual char* C::msg()

==============================================================================

/*
  I used to have code like class A, below, but g++ v. 3.0 will no longer
  compile it because of the abstract method in C (even though the
definition
  of A<C,true>::newT() will never try to instantiate an object of type C).

  To try to get around this issue, I attempted to modify to class B, but
  compiling reports:

t.cc:42: no `T* B<T, true>::newT()' member function declared in class `B<T,

   true>'
t.cc:42: template definition of non-template `T* B<T, true>::newT()'
t.cc:45: no `T* B<T, false>::newT()' member function declared in class
`B<T, 
   false>'
t.cc:45: template definition of non-template `T* B<T, false>::newT()'

  Is it accurate to report that no such member function is declared?  I'm
  under the impression that this code should work.
*/

template<class T,bool ClassIsAbstract>
class A
{
public:
  T* newT()
  {
    if(ClassIsAbstract) return 0;
    else return new T();
  }
};

class C { public: virtual char* msg() = 0; };

A<C,true> a;

template<class T,bool ClassIsAbstract>
class B
{
public:
  T* newT();
};

template<class T>
T* B<T,true>::newT() { return 0; }

template<class T>
T* B<T,false>::newT() { return new T(); }


B<C,true> b;

int main()
{
  a.newT();
  return 0;
}