go-plugin-cpp

A CMake/C++ library that lets you write hashicorp/go-plugin plugins in C++, using gRPC as the transport (net/RPC is not supported).

How it works

go-plugin launches a plugin as a child process and communicates via gRPC over loopback TCP. The child process (plugin) signals readiness by printing a single handshake line to stdout:

CORE-PROTO|APP-PROTO|tcp|127.0.0.1:PORT|grpc|SERVER-CERT

This library handles:

• Magic-cookie validation – aborts startup if the binary is run directly rather than by a go-plugin host.
• Port selection – respects PLUGIN_MIN_PORT/PLUGIN_MAX_PORT if set by the host.
• Auto-mTLS – when the host sets PLUGIN_CLIENT_CERT, a fresh server certificate is generated and mutual TLS is configured automatically.
• Handshake line output – writes the correctly formatted line to stdout so the host can connect.
• Health-check service – the built-in gRPC health-check service is registered automatically.

Building

Prerequisites

• CMake ≥ 3.20
• A C++17 compiler
• vcpkg with the VCPKG_ROOT environment variable set (or pass -DCMAKE_TOOLCHAIN_FILE)

cmake -B build \
      -DCMAKE_TOOLCHAIN_FILE="$VCPKG_ROOT/scripts/buildsystems/vcpkg.cmake" \
      -DCMAKE_BUILD_TYPE=Release
cmake --build build -j

Running the tests

cd build
ctest --output-on-failure

Running the example

Build the project first, then:

cd example/host
go run . ../../build/example/greeter_plugin