C++ template class inheritance

Question

I have been porting some C++ code, which was written long time ago, and is normally compiled with Visual C++ (Visual Studio 7.1 version) and Intel C++ Compiler 11.0, the target platform is Linux (Suse x86-64), with GCC 4.3.2 and Intel C++ Compiler 11.1

The problem is that code like this

FileA.h

template<typename T, int dim>
class A
{
 public:
  A(){};
  ~A(){};
 protected:
  void foo1(){};
}

FileB.h

#include "FileA.h"
template<typename T>
class B : public A<T, 2>
{
 public:
  B(){};
  ~B(){};
  void foo(){ foo1(); }
}

main.cpp

#include "FileB.h"
int main()
{
 B<float> b = B<float>();
}

does not compile on Linux (Intel C++ 11.1, GCC 4.3.2), but perfectly compiles on Windows (Visual C++ 7.1, Intel C++ 11.0), althow it surely must not depend on platform. GCC tells that if I change foo1() to foo1(T a) it will work (and it does), but I can not change the code, and have to use Intel C++ for final release.

I would be glad if anyone could help with any advice.

Answer 1

foo1 is not a dependent expression so the base class, which is a dependent type, is not used to resolve the foo1 call.

As you can't change the code, you are stuffed. If you could change the code you would need to change the expression to be dependent. Typically this is done by changing it to this->foo1() .

Answer 2

This is a well-known problem with templates. It is explained in the C++ FAQ

Answer 3

On gcc 4.4.1 (os is Ubuntu) version I could turn the compile error into a compile warning, by using the -fpermissive option to the compiler.

Edit: The fact that some compiler accept it, doesn't mean it will continue to accept it in future versions.