Hi Michael, what target are you trying to compile for? If you want to build Haiku, you need to have "haiku" as target platform. If you use the pseudo targets "install-haiku", this will be done automatically for you. If you use the same tree from R5 and Dano, you would need to invoke "configure" again each time. Also, have you installed all of the GCC package? Ie libstdc++.r4.so and the cpp headers as well? Best regards, -Stephan