Question

If I have a class which will be compiled to a shared object.
The class is declared in a .h file and implemented in a .cpp file.

This class contains a couple of inline methods.

If I write some program that links with this shared library and includes the .h file,
I will get undefined reference errors when linking it.

Is that because there are no symbols exported for inline methods ?

Am I understanding this correctly ?

UPDATE: some example code below

somelib.h

#ifndef __ABC_LIB_H
#define __ABC_LIB_H
#include <iostream>
class ABC {
    ABC();
    ~ABC();
    inline void not_callable_outside_library();
    void callable_outside_library();
};
#endif

somelib.cpp

#include "somelib.h"
ABC::ABC() {}
ABC::~ABC() {}
void ABC::not_callable_outside_library(){ std::cout<<"not_callable_outside_library"<<std::endl; }
void ABC::callable_outside_library(){ std::cout<<"callable_outside_library"<<std::endl; }

program.cpp

#include "somelib.h"
int main() {
    ABC x;
    x.not_callable_outside_library();
    return 0;
};

Compile somelib.cpp as a shared library( .so object) and link it program.cpp then you get the binary called program.

Now you should get an undefined reference when linking.

Answer 1

Inline functions must be defined in header files. Contrast what you have to the following:

somelib.h:

#ifndef ABC_LIB_H
#define ABC_LIB_H

#include <iostream>
class ABC {
    ABC();
    ~ABC();
    void not_callable_outside_library();
    void callable_outside_library();
};

inline void ABC::not_callable_outside_library() {
    std::cout << "not_callable_outside_library\n";
}

#endif

somelib.cpp:

#include "somelib.h"

ABC::ABC() { }
ABC::~ABC() { }
void ABC::callable_outside_library() {
    std::cout << "callable_outside_library\n";
}

program.cpp:

#include "somelib.h"

int main() {
    ABC x;
    x.not_callable_outside_library();
}