Building nerves project with a dep on a zephyr project built with elixir_make

Nerves Forum Nerves Questions / Help
1

I have a zephyr project where I’m setting up the Makefile so that it can be built via elixir_make. It all works well when I build it from the local project with mix compile, but when I introduced it as a dependency to a nerves project, the zephyr build would fail.
The build failed with:

CMake Error at /home/jringle/zephyrproject/3.7.0/modules/lib/picolibc/CMakeLists.txt:46 (if):
  if given arguments:

    "STREQUAL" "arm64"

  Unknown arguments specified

The failing code reference by the error has this:

if(${CMAKE_SYSTEM_PROCESSOR} STREQUAL "arm64")
  set(CMAKE_SYSTEM_PROCESSOR "aarch64")
endif()

(there were also warnings that Zephyr would be ignoring CFLAGS, CXXFLAGS, CPPFLAGS and LDFLAGS)
After a bit of digging around, I found that nerves_system_br seems to be setting this in the environment:

CMAKE_TOOLCHAIN_FILE=/home/jringle/git/gridpoint-com/ec2k_firmware/deps/nerves_system_br/nerves-env.cmake

nerves-env.cmake is the culprit for changing CMAKE_SYSTEM_PROCESSOR that leads to the zephyr build error.

I was finally able to successfully build the zephyr project from my nerves project by adding this to the zephyr project’s Makefile:

unexport CMAKE_TOOLCHAIN_FILE CFLAGS CXXFLAGS CPPFLAGS LDFLAGS

I’m wondering if anyone had thoughts on whether this was an appropriate way to handle this situation, or if there is a different way that might work better?

2

This is an interesting setup where the Nerves-injected environment variables are unhelpful.

There might be other environment variables that you’ll need to unexport. The Nerves provided environment variables page has the full list.

What I think could be a little better is if you can clear out the environment variables in your elixir_make configuration via :make_env rather than unexporting variables in the Zephyr project Makefile. Set the value of each variable to nil to keep it unset.

I’m curious if setting all of the Nerves-provided environment variables to nil works rather than just the subset that you found. I hope it does, since this seems like an all-or-none situation.

If using :make_env works for you, I’d like to make this easier in Nerves and provide a function for getting the list of all environment variables so that everyone who has a similar setup doesn’t need to manually list out all of the important variables. WDYT?

3

I removed the unexport line in the Makefile and then set :make_env to:

    %{
      "BOARD" => "edge",
      "CMAKE_TOOLCHAIN_FILE" => nil,
      "CFLAGS" => nil,
      "CXXFLAGS" => nil,
      "CPPFLAGS" => nil,
      "LDFLAGS" => nil
    }

And that worked as well

4

I also tried setting all of the Nerves-provided environment variables to nil as well, and that worked just fine.

5

Nice. I’m going to move work on this to Add helper functions to access Nerves-set environment variables · Issue #1003 · nerves-project/nerves · GitHub so we can get you and others who run into this an easier-to-maintain solution.

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