If you have receiving a "It seems that this project has not been built yet. Do you want to build it now?" message. Do:
I could resolve this problem doing the next:I installed the synaptic. Logged in as sudo, type: apt-get install synaptic. Type in the search field: g++. With the right button, mark "select for install", then press "mark". After that, press apply. Open the Codeblocks and test.