Code::Blocks - how to compile multiple source files

Here is what worked for me:

Go to the left panel that says projects, and right-click on .cpp file. Select properties, then go to build. Check the boxes under the heading Belongs in Targets: "Debug" and "Release"

I had a similar problem when creating my first multi source code project. i believe the problem you are having is not with the linking but with you #include statement for me the directory's were different to what i expected. to include the header file in a project i had to write #include "include/other.h" have a look at how your folder system is constructed....if you could post what folders/directory`s you have in the project i might be able to give you a better answer.