linker error building code with boost filesystem

[GaryE]

Hello:
I am having trouble linking a couple of files using the boost::filesystem.
I am using MSVC 6.0.
Here is an abbreviated version of my problem:

foo.h:

#ifndef __FOO_ 
#define __FOO_ 
#include "boost/filesystem.hpp" 
class foo 
{ 
public 
/*stuff*/ 
private 
boost::filesystem::path m_path; 
}; 
#endif 
 

bar.h:

#ifndef __BAR_ 
#define __BAR_ 
class foo; 
class bar 
{ 
public 
/*stuff*/ 
private 
foo* m_fooPtr; 
}; 
#endif 
 

bar.cpp:

#include "foo.h" 
/*use foo a lot*/ 
 
 

Here is the build result:

bar.obj : error LNK2005: "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl boost::filesystem::extension(class boost::filesystem::basic_path<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,struct boost::filesystem::path_traits> const &)" (?extension@filesystem@boost@@YA?AV?$basic_string@ DU?$char_traits@D@std@@V?$allocator@D@2@@std@@ABV? $basic_path@V?$basic_string@DU?$char_traits@D@std@ @V?$allocator@D@2@@std@@Upath_traits@filesystem@bo ost@@@12@@Z) already defined in foo.obj
bar.obj : error LNK2005: "class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __cdecl boost::filesystem::basename(class boost::filesystem::basic_path<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,struct boost::filesystem::path_traits> const &)" (?basename@filesystem@boost@@YA?AV?$basic_string@D U?$char_traits@D@std@@V?$allocator@D@2@@std@@ABV?$ basic_path@V?$basic_string@DU?$char_traits@D@std@@ V?$allocator@D@2@@std@@Upath_traits@filesystem@boo st@@@12@@Z) already defined in foo.obj
Debug/FooBar.exe : fatal error LNK1169: one or more multiply defined symbols found

Any ideas on what the problem is?
Thanks

[weaknessforcats]

You need to #include <string>.

[GaryE]

Thanks, but that still doesn't work.

[weaknessforcats]

And you have:

using namespace std;
 

Yes?

[GaryE]

Yes. This makes no difference.

[weaknessforcats]

This code:

boost::filesystem::path m_path; 
 

requires a class or namespace named boost plus a nestted class or namespace named filesystem plsu a nested class or namespace named path.

What does this thing have in it?

#include "boost/filesystem.hpp" 
 

Also, I would like to see the entire bar.cpp since that is what is being compiled.