C++ Language Support

C++ Language Support

Status: ✅ Full Support
Examples:

• examples/cpp-basic/
• examples/cpp-grpc/

C++ support includes the complete Protocol Buffer ecosystem with gRPC, CMake integration, and embedded-friendly alternatives like nanopb.

Available Plugins

Core Plugins

Plugin	Description	Generated Files
protoc	Base message generation	*.pb.cc, *.pb.h
grpc_cpp_plugin	gRPC service generation	*.grpc.pb.cc, *.grpc.pb.h

Embedded & Alternative Plugins

Plugin	Description	Generated Files
nanopb	Embedded C/C++ (minimal RAM)	*.pb.c, *.pb.h
protobuf-c	Pure C code generation	*.pb-c.c, *.pb-c.h

Configuration

Basic Configuration

languages.cpp = {
  enable = true;
  outputPath = "gen/cpp";
  standard = "c++17";
  optimizeFor = "SPEED";
};

Full Configuration Example

languages.cpp = {
  enable = true;
  outputPath = "gen/cpp";

  # Protobuf version selection
  protobufVersion = "latest"; # Options: "3.21", "3.25", "3.27", "4.25", "5.29", "latest"

  # C++ standard and optimization
  standard = "c++17"; # Options: "c++17", "c++20", "c++23"
  optimizeFor = "SPEED"; # Options: "SPEED", "CODE_SIZE", "LITE_RUNTIME"
  runtime = "full"; # Options: "full", "lite"

  # Build system integration
  cmakeIntegration = true;
  pkgConfigIntegration = true;

  # Performance options
  arenaAllocation = false; # Enable arena allocation for better performance

  # Additional include paths
  includePaths = [
    "/usr/local/include"
    "./third_party"
  ];

  # gRPC support
  grpc = {
    enable = true;
    generateMockCode = true; # Generate mock code for testing
    options = [
      "generate_mock_code=true"
    ];
  };

  # Embedded C/C++ support
  nanopb = {
    enable = true;
    options = [
      "max_size=1024"
      "max_count=16"
    ];
  };

  # Pure C support
  protobuf-c = {
    enable = false;
    options = [];
  };
};

C++ Standards Support

Bufrnix supports all modern C++ standards:

• C++17: Default, widely supported
• C++20: Modern features like concepts and coroutines
• C++23: Latest standard with additional features

Optimization Modes

Mode	Description	Use Case
SPEED	Optimize for execution speed (default)	Server applications
CODE_SIZE	Optimize for smaller binary size	Mobile/embedded devices
LITE_RUNTIME	Use lite runtime (smaller binary, fewer features)	Resource-constrained

Build System Integration

CMake Integration

When cmakeIntegration is enabled, Bufrnix generates CMake configuration files:

# FindProtobuf.cmake generated content
find_package(Protobuf REQUIRED)
find_package(gRPC REQUIRED)

# Include generated proto headers
include_directories(${CMAKE_CURRENT_SOURCE_DIR}/gen/cpp)

# Link against protobuf libraries
target_link_libraries(myapp
  protobuf::libprotobuf
  gRPC::grpc++
)

pkg-config Integration

When pkgConfigIntegration is enabled, .pc files are generated for easy library discovery.

gRPC Support

Enable gRPC to generate service stubs and client code:

grpc = {
  enable = true;
  generateMockCode = true; # Generate Google Mock compatible mocks
};

Generated files include:

• Service interfaces (*.grpc.pb.h)
• Client and server implementations (*.grpc.pb.cc)
• Mock classes for testing (when enabled)

Embedded Development

nanopb

For embedded systems with limited RAM:

nanopb = {
  enable = true;
  options = [
    "max_size=1024"      # Maximum message size
    "max_count=16"       # Maximum repeated field count
    "long_names=false"   # Use shorter field names
  ];
};

protobuf-c

For pure C environments:

protobuf-c = {
  enable = true;
  options = [];
};

Example Usage

Basic Messages

flake.nix

{
  languages.cpp = {
    enable = true;
    outputPath = "src/proto";
    standard = "c++17";
  };
}

main.cpp

#include "example.pb.h"

int main() {
  example::v1::User user;
  user.set_id(123);
  user.set_name("Alice");

  std::string serialized;
  user.SerializeToString(&serialized);

  return 0;
}

gRPC Services

flake.nix

{
  languages.cpp = {
    enable = true;
    grpc.enable = true;
    standard = "c++20";
  };
}

server.cpp

#include "service.grpc.pb.h"
#include <grpcpp/grpcpp.h>

class MyServiceImpl final : public MyService::Service {
  grpc::Status GetUser(grpc::ServerContext* context,
                      const GetUserRequest* request,
                      GetUserResponse* response) override {
    response->mutable_user()->set_id(request->id());
    response->mutable_user()->set_name("User " + std::to_string(request->id()));
    return grpc::Status::OK;
  }
};

Embedded (nanopb)

flake.nix

{
  languages.cpp = {
    enable = true;
    nanopb.enable = true;
    nanopb.options = [
      "max_size=256"
      "max_count=8"
    ];
  };
}

embedded.c

#include "pb_encode.h"
#include "pb_decode.h"
#include "message.pb.h"

void encode_message(uint8_t *buffer, size_t buffer_size) {
  Message msg = Message_init_zero;
  msg.value = 42;

  pb_ostream_t stream = pb_ostream_from_buffer(buffer, buffer_size);
  pb_encode(&stream, Message_fields, &msg);
}

Best Practices

1. Choose the Right Runtime: Use lite runtime for mobile/embedded, full runtime for servers
2. Optimize Appropriately: Use SPEED for servers, CODE_SIZE for embedded
3. Enable Arena Allocation: For high-performance scenarios with many small allocations
4. Use Modern C++: Prefer C++17 or newer for better language features
5. CMake Integration: Enable for easier build system integration

Troubleshooting

Common Issues

1. Protobuf Version Mismatch

   # Ensure consistent versions
   protobufVersion = "3.27";  # Match your system protobuf

2. Missing Headers

   # Add include paths
   includePaths = [
     "${pkgs.protobuf}/include"
     "./third_party/protobuf"
   ];

3. gRPC Compilation Errors

   # Ensure gRPC is enabled with matching protobuf version
   grpc.enable = true;
   protobufVersion = "3.27";  # Must match gRPC's protobuf dependency

See Also

• protobuf C++ Tutorial
• gRPC C++ Documentation
• nanopb Documentation
• CMake Integration Guide