Build as a CMake subdirectory

This is one of the two ways to integrate nano-ros into a C or C++ project, and the lower-level one: the repo’s top-level CMakeLists.txt exposes everything via add_subdirectory(...). The higher-level, ament-shaped alternative is find_package(nano_ros REQUIRED) — nano_rosConfig.cmake at the checkout root, located via nano_ros_ROOT (RFC-0048) — which every in-tree example now uses. Either way there is NO install step: phase-140 removed the install prefix and the old find_package(NanoRos) (capital) config pipeline. Vendoring the repo into a company tree (pinning, offline CI, upgrade workflow) has its own page: Integrating into a Vendored Tree.

Layout

my_app/
├── CMakeLists.txt
├── main.c
└── third_party/
    └── nano-ros/        # git clone / git submodule of this repo

User project `CMakeLists.txt`

cmake_minimum_required(VERSION 3.22)
project(my_app C)

# Pick platform + RMW BEFORE add_subdirectory.
set(NANO_ROS_PLATFORM posix)   # posix | freertos | nuttx | threadx | zephyr | baremetal
set(NANO_ROS_RMW     zenoh)    # zenoh | xrce | cyclonedds

add_subdirectory(third_party/nano-ros nano_ros)

add_executable(my_app main.c)
target_link_libraries(my_app PRIVATE NanoRos::NanoRos)
if(COMMAND nros_platform_link_app)   # defined by zephyr/threadx platforms only
    nros_platform_link_app(my_app)
endif()

# Optional — generate C bindings for ROS 2 .msg / .srv / .action files.
# (LANGUAGE defaults to CPP; full spelling table → user-guide
# "Message Generation".)
nano_ros_generate_interfaces(std_msgs LANGUAGE C
    DEPENDENCIES builtin_interfaces)
target_link_libraries(my_app PRIVATE std_msgs__nano_ros_c)

That’s the whole story for the host-POSIX / zenoh case. CMake’s transitive target propagation pulls in libnros_c.a, libnros_rmw_zenoh_staticlib.a, the POSIX platform shim, system libraries (pthread, dl, m), and the per-build nros_config_generated.h header automatically.

Cache variables

Variable	Default	Values
`NANO_ROS_PLATFORM`	`posix`	`posix`, `freertos`, `nuttx`, `threadx`, `esp_idf` (legacy spellings: `freertos_armcm3`, `nuttx_armv7a`, `threadx_linux`, `threadx_riscv64`). Zephyr and bare-metal are not add_subdirectory platforms — they enter via the Zephyr module / cargo directly
`NANO_ROS_BOARD`	(unset)	required for `threadx` (`threadx-linux` or `riscv64-qemu`)
`NANO_ROS_SKIP_BOOTSTRAP`	`OFF`	`ON` skips the configure-time bootstrap (git submodule updates + a possible network FetchContent of Corrosion). Required for air-gapped/mirrored CI — pre-seed submodules and install Corrosion first (`nros setup --tool corrosion`)
`NANO_ROS_FEATURES`	(empty)	extra cargo features forwarded to the Rust build
`NANO_ROS_RMW`	`zenoh`	`zenoh`, `dds`, `xrce`, `cyclonedds`
`NANO_ROS_ROS_EDITION`	`humble`	`humble`, `iron`, `jazzy`
`NANO_ROS_BUILD_CODEGEN`	`ON`	`ON` / `OFF`

Variables MUST be set(...) BEFORE add_subdirectory(...) — the sub-project consumes them at include time.

What about installing?

Phase-140 deleted every nano-ros-side install(...) rule. nano-ros is consumed in source form — never out of an installed prefix. If you need a shippable artefact, your user project owns the install layout; ship your binary, not nano-ros itself.

For RTOS users who want a more idiomatic surface than raw add_subdirectory, see the integration shells under integrations/<rtos>/ — they translate west / esp-idf / NuttX / PX4 manifests into the same root CMake. Each shell is a ~20-line wrapper around add_subdirectory(<repo>).

Worked example

The examples/native/c/talker/CMakeLists.txt is the canonical copy-out template: it resolves the nano-ros checkout root once (-DNANO_ROS_ROOT cache var → NROS_REPO_DIR env var → in-repo walk-up), includes the workspace helpers, generates the message bindings (nros_find_interfaces), and declares the app via nano_ros_entry(...) — ~55 lines including codegen + per-app fixup. All in-tree C/C++ examples follow the same shape.

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