Toolchain and Presets

Both the toolchain file and the preset file are per-project artifacts that arrive from CubeMX. They are not shared, though in practice every project carries the same content.

`CMakePresets.json`

Two usable presets, both inheriting a hidden default:

{
  "name": "default", "hidden": true,
  "generator": "Ninja",
  "binaryDir": "${sourceDir}/build/${presetName}",
  "toolchainFile": "${sourceDir}/cmake/gcc-arm-none-eabi.cmake",
  "cacheVariables": { "CMAKE_EXPORT_COMPILE_COMMANDS": "ON" }
}

Preset	`CMAKE_BUILD_TYPE`	Optimization	Use it for
`Debug`	`Debug`	`-O0 -g3`	anything you intend to step through
`Release`	`RelWithDebInfo`	`-Os -g0`	flight builds

Release sets CMAKE_BUILD_TYPE=RelWithDebInfo, not Release, so a generator expression written as $<$<CONFIG:Release>:...> never fires. The project template accounts for this by matching both configurations:

target_compile_definitions(${CMAKE_PROJECT_NAME} PRIVATE
    STM32
    $<$<CONFIG:Debug>:DEBUG>
    $<$<CONFIG:Release,RelWithDebInfo>:RELEASE>
)

Keep that in mind when adding your own per-configuration settings. Note that nothing in the firmware currently guards on DEBUG or RELEASE; both are provided for you to use.

Build output always lands at:

<project>/build/<preset>/<target>.elf     e.g.  src/bmc/build/Debug/bmc.elf

The Toolchain File

cmake/gcc-arm-none-eabi.cmake is what every preset points at. The parts worth knowing:

Setting	Value
System	`CMAKE_SYSTEM_NAME Generic`, processor `arm`
Compilers	`arm-none-eabi-gcc`, `-g++`, `-objcopy`, `-size`
CPU flags	`-mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard`
C++ flags	C flags plus `-fno-rtti -fno-exceptions -fno-threadsafe-statics`
Linker	`-T ${CMAKE_SOURCE_DIR}/STM32G431XX_FLASH.ld`, `--specs=nano.specs`, `--gc-sections`
Try-compile	`STATIC_LIBRARY` (a freestanding target cannot link a test executable)

Two consequences worth remembering:

The compiler is resolved from PATH. The toolchain names the tools bare, so whichever arm-none-eabi-gcc comes first wins. /etc/profile.d/mrover-esw.sh puts CubeCLT ahead of the standalone fallback; ./scripts/doctor.sh warns when that ordering has gone stale.
The linker script path is fixed relative to the project root. Every project must keep its STM32G431XX_FLASH.ld at its own top level.

`starm-clang.cmake`

Every project also ships a toolchain file for ST’s LLVM distribution. No preset references it and build.sh has no way to select it, so it is inert. Using it means invoking CMake by hand with -DCMAKE_TOOLCHAIN_FILE=.