Question on explicit template expansion

[Garrett Kajmowicz <gkajmowi at tbaytel dot net>]

I'm working on the embedded C++ library at cxx.uclibc.org

As a part of my work, I've been pushing some of the common template expansions 
out into the binary library to reduce overall expansion.  This works well 
*except* for constructors and destructors.  I would like an explanation as to 
why the following occurs and what I can go to deal with it.


Given (say) class string, I have:

//In the header file

template<class Ch, class Tr, class A> class basic_string {
public:
	explicit basic_string(const A& al = A()) { return; }
	~basic_string() { }

//	<snip>
//	<snip>
//	<snip>

};

#ifndef __UCLIBCXX_COMPILE_STRING__
	template <> string::basic_string(const allocator<char> &);
	template <> string::~basic_string();
#endif

//End of header file


And then inside the source file for the library I have

//Source file

#define __UCLIBCXX_COMPILE_STRING__ 1
#include <string>

template string::basic_string(const allocator<char> &);
template string::~basic_string();

//End of source file

I do this for a large number of functions.  This allows me to use only one 
instance of the code (that I have to type out) while creating the required 
instances.

This seems to work for most code.  However, for constructors and destructors I 
am left with the following error messages when I go to use the library:


../include/string:71: warning: inline function `std::basic_string<Ch, Tr,
   A>::basic_string(const A&) [with Ch = char, Tr = std::char_traits<char>, A 
=
   std::allocator<char>]' used but never defined
../include/string:100: warning: inline function `std::basic_string<Ch, Tr,
   A>::~basic_string() [with Ch = char, Tr = std::char_traits<char>, A =
   std::allocator<char>]' used but never defined


Any thoughts as to why this happens, and why it only happens for constructors 
and destructors.


Thanks.

-	Garrett Kajmowicz