Build a C++ message consumer

Build an executable that encodes and decodes the Reading message from the Python quickstart. Run these commands in that message project's directory, with the generator environment active.

Prepare the native libraries

Provide CMake 3.20 or newer and a C++17 compiler with C compiler support. On macOS, Apple's SDK and command-line tools are also required. Install the native Python dependencies using the wheel built in the installation guide. Replace the wheel path below with its absolute path.

python -m pip install '/path/to/dimos_cdrgen-0.1.0-py3-none-any.whl[native]'
python - <<'PY'
from pathlib import Path
from dimos_cdrgen.native_build import prepare_cpp, write_cmake_toolchain

prefix = prepare_cpp(Path("build/message-source"))
write_cmake_toolchain(prefix, Path("build/acme-toolchain.cmake"))
print(prefix)
PY

This step fetches and verifies pinned upstream sources, compiles the libraries, and prints the installation prefix. It does not install a system toolchain. To reuse verified sources and completed builds offline, pass offline=True and a populated cache=Path(...) to prepare_cpp().

Create the executable

Create CMakeLists.txt:

cmake_minimum_required(VERSION 3.20)
project(reader LANGUAGES CXX)
find_package(acme CONFIG REQUIRED)
add_executable(reader main.cpp)
target_compile_features(reader PRIVATE cxx_std_17)
target_link_libraries(reader PRIVATE acme::messages)

Create main.cpp:

#include <example_msgs/msg/reading.hpp>
#include <dimos_cdrgen/cdr.hpp>

int main() {
    example_msgs::msg::Reading message;
    message.sequence = 1;
    message.value = 21.5;
    auto wire = dimos::cdr::cdr_encode(message);
    auto restored = dimos::cdr::cdr_decode<example_msgs::msg::Reading>(wire);
    return restored.sequence == 1 && restored.value == 21.5 ? 0 : 1;
}

Compile and run

cmake -S . -B build/app -DCMAKE_TOOLCHAIN_FILE="$PWD/build/acme-toolchain.cmake"
cmake --build build/app
./build/app/reader

The executable exits with status 0 when the round trip succeeds. The exported toolchain supplies the package prefixes and saved target settings. The CDR header comes from this library and needs no DimOS SDK include path.