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    <p>There's a few errors here:</p> <p><strong>libshared.so is empty</strong></p> <p>Your Makefile doesn't actually link in the shared.o , it just creates an empty shared library. Change </p> <pre><code>g++ -g -ggdb -fPIC -rdynamic -shared -Lstatic -lstatic -o shared/libshared.so </code></pre> <p>to </p> <pre><code>g++ -g -ggdb -fPIC -rdynamic -shared -Lstatic -o shared/libshared.so shared/shared.o -lstatic </code></pre> <p>The -lstatic have to come after shared/shared.o as you have to specify static libraries in reverse order of their dependencies.</p> <p><strong>-fPIC is needed on all object files in a shared library</strong></p> <p>You create a shared library that links in a static library. That static library also have to be compiled with -fPIC, otherwise you're creating a shared library where some parts of it cannot be relocated. Change</p> <pre><code>g++ -g -ggdb -c static/static.cpp -o static/static.o </code></pre> <p>to </p> <pre><code>g++ -fPIC -g -ggdb -c static/static.cpp -o static/static.o </code></pre> <p><strong>C++ symbols get mangled</strong></p> <p>As you're creating a shared library from C++ code, function names and similar gets <a href="http://en.wikipedia.org/wiki/Name_mangling" rel="noreferrer">mangeled</a> This means there is no function name matching the string "function_inside_static_lib" which you try to dynamically load. run nm on the static library, you'll see it's actually named "_Z26function_inside_static_libii" . You can run nm -C to pretty print C++ names.</p> <p>This means your code in app.cpp have to be:</p> <pre><code> function_inside_shared_lib = (int (*)(int, int))dlsym(handle, "_Z26function_inside_static_libii"); </code></pre> <p>This is one of the reasons it's often preferrable to export functions from shared objects using C instead of C++ if you want to dynamically (dlopen) fetch something from a shared library. The C++ name mangling have in the past varied from compiler to compiler, though these days they seem to have all agreed to a standard that won't be changing. With C it's simpler, and the symbols in the shared library will be the same as you gave them in your source code.</p>
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