Document the cmake build system

[astrogeco]

Describe the bug
Our documentation does not explain to users how the build system works and how to customize it for their needs

Expected behavior
A clear description and possibly some graphics showing how the different cmakelists files link with each other and how dependencies flow.

From CFS-40: Document dependencies based on features used (xxd for "embedded" files)

cFE/cmake/target/CMakeLists.txt

Line 229 in e80aae9

COMMAND xxd -i < "${FILESRC}" > "${CMAKE_CURRENT_BINARY_DIR}/embed/${EMBNAME}.inc"

It might make more sense to move this into the github.com/nasa/cFS instead

Additional context
Related to conversation started in #751

Reporter Info
Gerardo E. Cruz-Ortiz

[astrogeco]

@JandlynBentley-at-NASA this might be a good one for you to tackle

[CraigKnoblauch]

I'd like to second the need for this. I'm having a heck of a time figuring out what's needed to customize a build to my needs. @astrogeco What docs do your recommend right now that I could use?

[astrogeco]

I'd like to second the need for this. I'm having a heck of a time figuring out what's needed to customize a build to my needs. @astrogeco What docs do your recommend right now that I could use?

I'll have to defer to @jphickey since I can't think of anything other than the comments in the files inside cmake/sample_defs

[CraigKnoblauch]

OK great! In the meantime I can look over those comments.

…

On Mon, Jan 11, 2021 at 9:23 AM Gerardo E. Cruz-Ortiz < ***@***.***> wrote: I'd like to second the need for this. I'm having a heck of a time figuring out what's needed to customize a build to my needs. @astrogeco <https://github.com/astrogeco> What docs do your recommend right now that I could use? I'll have to defer to @jphickey <https://github.com/jphickey> since I can't think of anything other than the comments in the files inside cmake/sample_defs — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#760 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AF7NUNV2LT43TSUJAKISSJTSZMCW7ANCNFSM4OG7LZUA> .

[skliper]

@CraigKnoblauch - feel free to post a question here if there is something in particular you are struggling with. There's a handful of issues that I've marked as "questions" where specific behavior was explained, and getting a better sense of where the challenges are would help with identifying specific documentation needs.

[CraigKnoblauch]

@astrogeco @skliper I remember a version of cFS that had a setvars.sh script. Where is that file now? Or a better question, has that file's functionality been replaced by something else? Also, where can I find information about how I should set up my mission directory? It's obvious that I should have one, as a vanilla build is complaining about that, but I'm not sure where to start setting it up and telling the build system about it. Do you guys have any ideas?

[skliper]

setvars.sh was used in the "classic build" system before we transitioned to CMake. It is no longer necessary, and has been replaced by CMake. I'm not sure what you are asking about "mission directory", do you mean customizing "sample_defs" for your mission? If so I recommend starting from the "sample_defs" using the quick start steps documented in the https://github.com/nasa/cFS README, and replacing/updating whatever you need to for your mission.

[renn0xtek9]

Being new to this project and external, I agree that some doc on how the CMake ist structure would be very helpful.
Right now, it is not clear to me why the cfe/CMakeLists.txt is used recursively. (I don't grasp why it has to be so)
I have seen this strategy (to deal with multiple platform) in a few project before, but it turned out to be an anti pattern. It tend to confuse people and IDE. @astrogeco do you have some more information on this ?