Generate Code from C++ Classes

cpp-codegen-rs uses libclang to read C++ class definitions and generate code. Example use cases include the generation of Google Mock Classes, Reflection Libraries, (De)Serialization, RPC Frameworks, and anything else that suffers from a lack of proper compile-time reflection in C++. The underlying concept is that it's sometimes preferrable to use actual code as the IDL to generate these things as supposed to a dedicated IDL.

Project Status

This is currently alpha. Expect bugs and API changes.

Usage

cpp-codegen-rs is a source-to-source compiler. While the input has to be very specific (C++ classes), the output can be anything ranging from more C++ code, bindings for other languages to documentation.

The following example creates GoogleTest mock objects for C++ classes. Usually code generation is run before the actual compilation.

Given the following C++ header:

#pragma once

struct Interface {
    virtual ~Interface() = default;
    virtual void method(int foo) = 0;
    virtual int foo(double) = 0;
};

The corresponding GoogleTest mock object would look like this:

#pragma once
#include <gmock/gmock.h>

class MockInterface : public Interface {
  MOCK_METHOD1(method, void(int));
  MOCK_METHOD1(foo, void(double));
};

cpp-codegen-rs parses the C++ header, and creates a Model object out of the abstract syntax tree defined by the header. The Model is then passed to a template file. To achieve the desired transformation, a suitable template looks like this:

// THIS FILE IS GENERATED, CHANGING IT IS FUTILE
#pragma once
#include <gmock/gmock.h>

{{#each interfaces ~}}
class Mock{{name}} : public {{name}} {
{{#each methods ~}}
    MOCK_METHOD{{len arguments}}({{name}}, {{return_type}}({{#each arguments}}{{argument_type}}{{#unless @last}}, {{/unless}}{{/each}}));
{{/each ~}}
};
{{/each ~}}

The templating language is based on the HandleBars Rust library, which should be consulted for documentation on how to write templates. A complete template for GoogleTest mock objects, which also deals with namespaces and class templates, can be found in gmock.hbs.

In order to perform the actual compilation, cpp-codegen-rs is invoked with the following parameters

cpp_codegen interface.h -t templates/gmock.hbs

Generated code is written to stdout.

Distribution

My goal is to supply statically linked (against libclang) release binaries for Linux, OS X and Windows to ease deployment.

License

MIT