Linking onnx-light in C++

This page summarizes the design used to consume onnx-light as a standalone C++ library from another project.

Runnable examples are available in C++ onnx-light examples, including examples/load_onnx_light_time and examples/check_onnx_light_model.

Install and link model

From the repository root, install the C++ library with CMake:

cmake -S . -B build-install \
      -DCMAKE_BUILD_TYPE=Release \
      -DONNX_LIGHT_BUILD_PYTHON=OFF \
      -DCMAKE_INSTALL_PREFIX=/usr/local
cmake --build build-install
cmake --install build-install

Then downstream projects can rely on the exported CMake targets:

find_package(onnx_light REQUIRED)
target_link_libraries(my_target PRIVATE onnx_light::onnx_light)

Use onnx_light::onnx_light when the code needs higher-level ONNX features implemented in onnx_light/onnx_lib such as operator schemas, checker, shape inference, or version conversion.

For protobuf-compatible message parsing/serialization only, downstream code can link just the lighter proto target:

find_package(onnx_light REQUIRED)
target_link_libraries(my_target PRIVATE onnx_light::lib_onnx_proto)

That is sufficient when the program only manipulates ModelProto / GraphProto data and does not need any notion of operators.

For manual registration of lightweight math operator schemas without shape inference support, downstream code can link:

find_package(onnx_light REQUIRED)
target_link_libraries(my_target PRIVATE onnx_light::lib_onnx_op)

This keeps downstream CMake files independent from hardcoded include paths and library file names. If onnx-light is installed to a non-standard prefix, configure the downstream project with -DCMAKE_PREFIX_PATH=<prefix>.

Alternative without install

For monorepos or local development, a downstream CMake project can also include onnx-light directly:

set(ONNX_LIGHT_BUILD_PYTHON OFF CACHE BOOL "" FORCE)
add_subdirectory(path/to/onnx-light)
target_link_libraries(my_target PRIVATE lib_onnx_lib)

Use the in-tree lib_onnx_proto target instead when only proto parsing/serialization is needed. This uses the in-tree build targets instead of find_package.

Excerpt from the example project

The example CMake project in examples/load_onnx_light_time uses exactly that pattern:

cmake_minimum_required(VERSION 3.15)
project(load_onnx_light_time LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(onnx_light REQUIRED)

add_executable(load_onnx_light_time main.cc)
target_link_libraries(load_onnx_light_time PRIVATE onnx_light::lib_onnx_proto)

See also

• Standalone C++ example: load an ONNX file with onnx_light