[Cmake] Help with first project

[Brad King]

Matt Junkemail wrote:
> Hi,
> 
> I'm new at using CMake (and I really like what I see!)
>  Here is a question I haven't been able to solve.
> 
> I have a project that I've been working on for a while
> in Visual C++.  I
> would like to work on the same project within Linux
> using gcc and CMake.
> 
> I have several files within the project's root
> directory and several sub-directories that contain
> source files as well.
> 
> The project is named "Engine" and resides in a
> directory called Engine, which contains Engine.cpp and
> Engine.h files.  Within this directory, the two
> sub-directories are called "Tag" and "SOE", both
> containing several matching .h and .cpp files.
> 
> I have in the Engine directory a CMakeLists.txt file
> that contains the
> following:
> 
> PROJECT(Engine)
> 
> SUBDIRS(Tag SOE)
> INCLUDE_DIRECTORIES(Tag SOE)
> SET(Engine_source Engine.cpp)
> 
> ADD_EXECUTABLE(Engine ${Engine_source})
> 
> The Tag and SOE directories also contain
> CMakeLists.txt files.  They add to the Engine_source
> variable:
> 
> SET(Engine_source ${Engine_source} Tag.cpp)
> 
> and:
> 
> SET(Engine_source ${Engine_source} SOE.cpp)
> 
> That's the only command in the file.
> 
> CMake generates a make file, but uponing making it, I
> receive errors that within Engine.o, I have an
> undefined reference to Tag.
> 
> Within the Tag and SOE directories, there are no .o
> files.  So these files are not being compiled.
> 
> I have also tried using the AUX_SOURCE_DIRECTORY
> command
> within the root CMakeLists.txt file.
> 
> So basically I need to compile a "main" file in the
> main directory that uses objects from classes in
> separate source files (.cpp and .h) that reside in
> sub-directories.  I don't want to compile and link the
> sub-directory files as libraries.
> 
> Can somebody help with the scripts?

Directories in CMake projects may currently only depend on parent 
directories, not children.  You can solve your problem by moving the 
Engine executable source file into a third subdirectory.

-Brad