LNK 2001 unresolved external on NPPluginFuncs struct ptr as static class member [duplicate]

Question

This question already has answers here:

What is an undefined reference/unresolved external symbol error and how do I fix it? (38 answers)

Closed 8 years ago.

In my VS2010 DLL project i have an error, when compiling this project: LNK 2001 unresolved external on pFuncs member of my class:

class Foo
{
    // ...
    static NPPluginFuncs * pFuncs;
    // ...
};

Here a struct, defined in npfunctions.h:

typedef struct _NPPluginFuncs {
  uint16_t size;
  uint16_t version;
  NPP_NewProcPtr newp;
  NPP_DestroyProcPtr destroy;
  NPP_SetWindowProcPtr setwindow;
  NPP_NewStreamProcPtr newstream;
  NPP_DestroyStreamProcPtr destroystream;
  NPP_StreamAsFileProcPtr asfile;
  NPP_WriteReadyProcPtr writeready;
  NPP_WriteProcPtr write;
  NPP_PrintProcPtr print;
  NPP_HandleEventProcPtr event;
  NPP_URLNotifyProcPtr urlnotify;
  void* javaClass;
  NPP_GetValueProcPtr getvalue;
  NPP_SetValueProcPtr setvalue;
  NPP_GotFocusPtr gotfocus;
  NPP_LostFocusPtr lostfocus;
  NPP_URLRedirectNotifyPtr urlredirectnotify;
  NPP_ClearSiteDataPtr clearsitedata;
  NPP_GetSitesWithDataPtr getsiteswithdata;
  NPP_DidCompositePtr didComposite;
} NPPluginFuncs;

Answer 1

Static members of a struct (or class) are declared in the typedef struct { }; and needs to be defined explicitly once:

#include "npfunctions.h"

Foo::pFuncs = NULL;  // optional initialization


int main()
{
    Foo::pFuncs = new NPPluginFuncs;
}