Question

Consider this code

#include <iostream> 
#include <cstdio>
using namespace std;

class Dummy {
public:
    Dummy();
};

inline Dummy::Dummy() {
    printf("Wow! :Dummy rocks\n");
}

int main() {
    Dummy d;
}

All is good here!

Now I do this modification. I move the declaration of Dummy to “dummy.h”.

class Dummy {
public:
    Dummy();
};

And define the constructor Dummy() as following in “dummy.cpp”

#include "dummy.h"
inline Dummy::Dummy() {
    printf("Wow! :Dummy rocks\n");
}

And finally, I have my main file as:

#include <iostream> 
#include <cstdio>
#include "dummy.h"
using namespace std;

int main() {
    Dummy d;
}

It compiles fine, but I get a linker error complaining an undefined reference to Dummy::Dummy().

Any insights.

—

Answer 1

You have to put all inline functions (including methods and constructors/destructors) in a header file, where they are declared.

Though this code should work either way, with main() calling the constructor as if the inline keyword was not there. Are you sure you are passing object files from both compilation units to the linker?