[boost] Compiler deficiency for Quaternion library

From: Michael Stevens (support-1_at_[hidden])
Date: 2002-08-22 22:54:02

Hi All,

I am try to resolve some portability issues with Hubert's 
Quaternion/Octonian library. The aim is to get compatibility with 
GCC3.1/2 and VC7. The final problem is what I believe to be 
non-complient handling of explict specializations by both compilers. The 
Quaternion/Octonian library provides explicit specialsations of the 
quaternion/octonian class templates for the float, double and long 
double types. These specialisation provide additional type conversions 
so a portable solution would be handy.

It is easiest to show the compiler problem with the following code snippet

// explict.hpp Class with explict specialization
template <class T>
struct TC {
};

template <>
struct TC<int> {
    void f2();            // Decleration of class template 
specialisation member function
};

void TC<int>::f2()   // Definintion of class template specialisation 
member function
{}

The problem is that both compilers treat the template function 
definition as if it was an ordinary function definition. This is a big 
problem if the explict.hpp header is included in more then one 
compilation unit. The function is multiply defined and results in link 
errors.

The same problem does not occur if the definition is moved inline into 
the class template specialation definition. However this arangment would 
require restructing much of the quaternion/octonian headers.

Looking at the C++ standard I cannot see that the way the these 
compilers treat these definitions as ordinary function definitions is 
correct behaviour. Does anyone else have any more experience of this? 
Any suggestions/workarounds?

Thanks,
    Michael Stevens    Australian Center for Field Robotics