base.cpp

#include "base.h"
Base::Base() {}
Base::~Base() {}

base.h

class Base
{
public:
    Base();
    virtual ~Base();
};

derived.cpp

#include "base.h"

namespace {
    class LocalToTranslationUnit : public Base {
        public:
            LocalToTranslationUnit() {}
    };
}

void CLASS()
{
    LocalToTranslationUnit local;
}

Makefile

all: compile 

clean:
	rm -f *.o *.dylib *.app

compile: lib

lib: clang-lib gcc-lib

clang: clang-lib 

clang-lib:
	clang++ -c base.cpp -o base.clang.o -fvisibility=hidden -fvisibility-inlines-hidden 
	clang++ -c derived.cpp -o foo.clang.o -fvisibility=hidden -fvisibility-inlines-hidden -DCLASS=Foo
	clang++ -c derived.cpp -o bar.clang.o -fvisibility=hidden -fvisibility-inlines-hidden -DCLASS=Bar
	clang++ -dynamiclib base.clang.o foo.clang.o bar.clang.o -o libfoo.clang.dylib

gcc: gcc-lib 

gcc-lib:
	g++ -c base.cpp -o base.gcc.o -fvisibility=hidden -fvisibility-inlines-hidden
	g++ -c derived.cpp -o foo.gcc.o -fvisibility=hidden -fvisibility-inlines-hidden -DCLASS=Foo
	g++ -c derived.cpp -o bar.gcc.o -fvisibility=hidden -fvisibility-inlines-hidden -DCLASS=Bar
	g++ -dynamiclib base.gcc.o foo.gcc.o bar.gcc.o -o libfoo.gcc.dylib

nm:
	nm *.o | c++filt
	nm *.dylib | c++filt