Problem exporting boost.variant from dll

[yetanothertom]

Hi, all.

I have a boost::variant problem. I have a dll to which I've added a couple classes using boost::variant. Everything compiles fine, but during build, I get the following error:

NPoint.obj : error LNK2019: unresolved external symbol "public: class boost::variant<bool,unsigned char,double,float,short,int,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_> __thiscall neo::NPoint::getValue(void)" (?getValue@NPoint@neo@@QAE?AV?$variant@_NENMFHUvoid_@0detail@boost@@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@@boost@@XZ) referenced in function "public: bool __thiscall neo::NPoint::getWriteValue(class boost::variant<bool,unsigned char,double,float,short,int,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_,struct boost::detail::variant::void_> &)" (?getWriteValue@NPoint@neo@@QAE_NAAV?$variant@_NENMFHUvoid_@0detail@boost@@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@U1023@@boost@@@Z)

Here's how I've defined the variant in a header file that all classes in my project use:

#ifdef _NEO_EXPORTS
#define CLASS_DECLSPEC __declspec(dllexport)
#define EXPIMP_TEMPLATE
#else
#define CLASS_DECLSPEC __declspec(dllimport)
#define EXPIMP_TEMPLATE extern
#endif

#include <boost/variant.hpp>

typedef bool NBitValue;
typedef unsigned char NByteValue;
typedef double NDFloatValue;
typedef float NFloatValue;
typedef short int NWordValue;
typedef int NDWordValue;


// Instantiate template classes for export
EXPIMP_TEMPLATE template class CLASS_DECLSPEC boost::variant < NBitValue, NByteValue, NDFloatValue,NFloatValue, NWordValue, NDWordValue>;

typedef boost::variant <NBitValue, NByteValue, NDFloatValue,
NFloatValue, NWordValue, NDWordValue> NValue;


An example of how it is used in other classes:

namespace neo
{
class CLASS_DECLSPEC NPoint :
public NValueBase
{
public:

.....
bool getWriteValue(NValue& t);

Compiles fine, but the linker goes on to say:

" referenced in function "public: bool __thiscall neo::NPoint::getWriteValue .."


I've been using boost for the past two months in this project with no problem, but now I can't get this to link. I'm sure I'm doing something stupid. Does anyone have any insight?

Thanks in advance,
Tom

[cran]

you might need to link another library... possibly one with variant in it... I still have yet to use boost, so can't say much. Did you compile all the libraries already and did you link the appropriate ones?

[yetanothertom]

Is there an additional library for Boost.Variant? There isn't one listed in the "documentation," although I use the term documentation loosely in this case.

I am using some boost features that require lib files, and have included the lib directory in my project. They do not have a problem. Perhaps there is a .lib file I need to specifically mention in the linker settings? I can find no mention of one in the doc.

[cran]

Hmm, where is getWriteValue() defined at?

[yetanothertom]

Do you mean is it in an external library? No, it is part of the same project; it's not external to the project Boost.Variant is being used in.

[yetanothertom]

Found it. I had a problem in a class declaration that was using Variant. The error message was misleading.

Thanks!