Standalone C++ example: print a proto for debugging

This page documents examples/print_proto_debug (view on GitHub), a self-contained CMake project that demonstrates how to dump any ONNX proto as readable text from C++.

The example purposely links against onnx_light::lib_onnx_proto only: no operator schemas, no shape inference, no checker, and no backend kernels are needed to print a generated protobuf message for debugging.

Step 1 – Install the C++ library

From the onnx-light repository root, build and install the static library and its public headers. The Python extension is not required:

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

Step 2 – Build the example

Point CMAKE_PREFIX_PATH at the install prefix chosen above:

cmake -S examples/print_proto_debug -B build-print-proto-debug \
      -DCMAKE_BUILD_TYPE=Release \
      -DCMAKE_PREFIX_PATH=/usr/local
cmake --build build-print-proto-debug

Step 3 – Run the example

./build-print-proto-debug/print_proto_debug

#include "onnx.h"
#include <iostream>
#include <sstream>

namespace onnx_light = ONNX_LIGHT_NAMESPACE;

int main() {
  onnx_light::NodeProto node;
  node.set_name("relu1");
  node.set_op_type("Relu");
  *node.add_input() = "X";
  *node.add_output() = "Y";
  node.set_doc_string("Simple ReLU activation");

  onnx_light::utils::PrintOptions options;
  std::stringstream ss;
  node.PrintToStringStream(ss, options);
  std::cout << ss.str() << "\n";
  return 0;
}

CMakeLists.txt

The example CMake project uses find_package to locate the installed library and links against the exported onnx_light::lib_onnx_proto target. That is the minimum dependency set required here because the example only formats generated protobuf-compatible messages:

cmake_minimum_required(VERSION 3.15)
project(print_proto_debug LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(onnx_light REQUIRED)

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

Example output:

input: "X"
output: "Y"
name: "relu1"
op_type: "Relu"
doc_string: "Simple ReLU activation"

See also

• onnx::ProtoDebugString (from proto_utils.h) is a convenience helper that internally calls PrintToStringStream and returns a single std::string.