c++ - Static lib loading related issue -

suppose want version libs in binaries made. static libs, thought approach work not:

libinfo.h - base class libinfo classes. registers object in gvlibinfo vector when child constructed.

#ifndef iface_h #define iface_h  #include <vector>  class libinfo; extern std::vector<libinfo*> gvlibinfo;  class libinfo {     public:         virtual int getversion() = 0;         void reglib()         {             gvlibinfo.push_back(this);         }          libinfo()         {             reglib();         }         virtual ~libinfo()         {} };   #endif 

lib1.h - derived libinfo , creates object l1. lib2.h same except getversion returns 2.

#ifndef lib1_h #define lib1_h  #include "libinfo.h"  class lib1 : public libinfo {     public:         int getversion()         {             return 1;         }      private: };  lib1 l1;  #endif 

main.cpp

#include "lib1.h" #include <iostream> using namespace std;  vector<libinfo*> gvlibinfo;  int main() {            for(vector<libinfo*>::iterator = gvlibinfo.begin(); != gvlibinfo.end(); it++)     {                cout << (*it)->getversion() << endl;     }      return 0; } 

compiling -

g++ -c lib1.h -o lib1.o g++ -c lib2.h -o lib2.o ar cr lib.a lib1.o lib2.o g++ main.cpp -o app -l/home/duminda/statictest/lib.a 

when run, nothing happens. thought maybe due 1 of several reasons:

1. at time lib1 l1 made, gvlibinfo has not been constructed.
2. i saw somewhere linker remove unused variables static lib. however, when run on binary nm shows :

0000000000603280 b gvlibinfo

0000000000603270 b l1

0000000000603278 b l2

i guess l1 & l2(the corresponding object of class lib2 there 'b' flag mean? 3. else don't know.

the first answer question propose use --whole-archive flag. main difference is, instead of referring external object, library refers external function.

linking not occur -l, -l, i.e. should :

-l/path/to/libdir -lname 

if library :

/path/to/libdir/libname.a