Implementation:Alibaba MNN FlatBuffers IDL Gen CPP

Knowledge Sources	Alibaba_MNN FlatBuffers
Domains	Serialization, Code_Generation
Last Updated	2026-02-10 12:00 GMT

Overview

C++ code generator backend that emits header files with zero-copy accessors and builder classes from FlatBuffers schemas.

Description

idl_gen_cpp.cpp implements the C++ code generation backend for flatc. It traverses the parsed schema tree and emits a single _generated.h header containing struct accessors, table accessors with vtable lookups, builder classes, verifier methods, and optional mutation accessors. This is the most critical generator for MNN since the framework uses C++ generated code for all model file I/O.

Usage

Vendored dependency used internally by MNN for model serialization. Not directly imported by end users.

Code Reference

Source Location

• Repository: Alibaba_MNN
• File: 3rd_party/flatbuffers/src/idl_gen_cpp.cpp
• Lines: 1-2763

Signature

namespace flatbuffers {
  bool GenerateCPP(const Parser &parser,
                   const std::string &path,
                   const std::string &file_name);
}

Import

#include "flatbuffers/idl.h"
// Generator invoked internally by flatc

I/O Contract

Input	Output
Parsed Parser object with schema definitions	*_generated.h C++ header file with accessors and builders

Usage Examples

// Invoked by flatc, not directly:
// flatc --cpp --gen-mutable --scoped-enums model.fbs

// Internally:
flatbuffers::Parser parser;
parser.Parse(schema);
flatbuffers::GenerateCPP(parser, output_path, file_name);

Related Pages

• Environment:Alibaba_MNN_CPU_Build_Environment