This first archive is build from:

libArchive1/libArchive1.h

#include <string>
std::string GetHello();

libArchive1/libArchive1.c

#include "libArchive1.h"
std::string GetHello() { return std::string("Hello "); }

You can compile these files to an archive using these 2 commands:

g++ -c libArchive1/libArchive1.c -o
libArchive1/libArchive1.o ar rcs libArchive1/libArchive1.a
libArchive1/libArchive1.o

Similar library to libArchive1.a with use of the GetHello() function:

libArchive2/libArchive2.h

#include "libArchive1.h"
std::string GetHelloWorld();

libArchive2/libArchive2.c

#include "libArchive2.h"
std::string GetHelloWorld() { return GetHello() + std::string("World!\n"); }

Compile by:

g++ -c libArchive2/libArchive2.c -IlibArchive1 -o libArchive2/libArchive2.o
ar rcs libArchive2/libArchive2.a libArchive2/libArchive2.o

This will require to provide the parameter -I so the compiler knows where to get the file libArchive1.h.

Small application printing “Hello World!” to stdout using the GetHelloWorld() function.

printHelloWorld.c

#include <iostream>         // for cout
#include "libArchive2.h"
int main(int argc, char* argv[]) {
   std::cout << GetHelloWorld();
   return 0;
}

Now here is where the problem did arise, compiling the application. This is what I did:

g++ helloWorldApp/printHelloWorld.c -IlibArchive1 -IlibArchive2 -LlibArchive1 -LlibArchive2 -lArchive1 -lArchive2 -o helloWorld.app

The arguments -lArchive1 and -lArchive2 will tell the compiler to link in libArchive1 and libArchive1. But I got the following

error: undefined reference to GetHello()

After a long search (the application I was working on was a lot more complex, so many things could have been wrong), I found the order of importing libraries with the -l argument matter. So after switching the order of -lArchive1 -lArchive2, the application got compiled and did print the text “Hello World!” when running it.