In terms of building firmware, what is Make's, Ninja's, and CMake's responsibility?

[jrn90]

We need to differentiate Make, Ninja, and CMake in PX4 in order to better understand the build system in place.

Acceptance Criteria

• [x] What is Make's responsibilities for building PX4 firmware?
• [x] What is Ninja's responsibilities for building PX4 firmware?
• [x] What is CMake's responsibilities for building PX4 firmware?

[jrn90]

Ninja

Ninja is used as the primary, and preferred, build system for PX4. It's primary focus is speed. The Ninja build files are generated using CMake Generators. You can see the generated files in builds under *.ninja.

Make

Make is used as another build system for PX4. Make is the default build system for CMake. It can be used to build PX4 but Ninja is the primary build system for PX4.

CMake

CMake is a generator of build systems. It is used in PX4 to generate Make & Ninja build files. It is useful for PX4 since it creates cross-platform builds out of the same CMakeLists.txt file which allows PX4 to compile on Windows, Mac, and Linux.

Under the hood Make & Ninja use the GCC compiler to compile PX4.

Makefile

PX4 has a somewhat complex Makefile. There are a few things of note relating to building the firmware:

• All the board targets are "defined" by finding the .px4board configuration files in the boards folder. Adding a .px4board to the boards folder will automatically add that new board to Make.
• All board targets call a function defined in the Makefile called cmake-build.
• The cmake-build function sets up the cmake args, build directory, determines whether to use Make or Ninja, sets up CMake cache, and builds the project (with Make or Ninja)
• Make and Ninja are not explicitly called by the Makefile. The cmake-build function uses the cmake --build function to call the appropriate build system.

[jrn90]

Captured in wiki.