clang-mirror

clang-mirror is a Clang-based code generation tool that produces AST-driven IDs and metadata registration code to enable portable runtime reflection for C++ without compiler extensions.

It enables user-defined types, functions, and member functions to be discovered and invoked at runtime using compile-time validated IDs – without manual registration.

After the generated ID headers and registration sources are built into your project, reflected entities can be discovered and invoked at runtime. Registration is initialized lazily on the first call to cxx::mirror(), so no runtime cost is incurred if reflection is never used.

Example

Given a function :

std::string complexToStr(float real, float img);

You can call it at runtime by id :

#include "cxx_mirror.h"  // The generated header.
// ...

{
    // Find the function using its AST-generated, compile-time-checked, constexpr ID.
    auto cToStr = cxx::mirror().getFunction(cxx::fn::complexToStr::id)
                               ->argsT<float, float>()
                               .returnT<std::string>();

    // `cToStr` is a functor that encapsulates the underlying function pointer.
    if (cToStr) {  // Functor valid?
        std::string result = cToStr(61, 35);  // Works!
    }
}

Reflect any class or struct:

class Person {
public:
    std::string getName();
// ...
};

Call a member function by id:

// Navigate via Intellisense to locate the IDs.
auto clsId = cxx::type::Person::id;
auto fnId  = cxx::type::Person::fn::getName::id;

// Lookup the class by ID.
auto classPerson = cxx::mirror().getRecord(clsId);
auto getName = classPerson->getMethod(fnId);  // Query method metadata.

// Get functor from metadata.
auto method = getName->targetT<Person>()
                     .argsT()
                     .returnT<std::string>();
					 
if(method) {  // Functor valid?
    std::string name = method(personObj)();  // invokes Person::getName()
}

How it works?

clang-mirror generates the boilerplate registration code required by the Reflection Template Library (RTL) to enable a runtime reflection system for C++ projects.

Given one or more source files, it uses the clang frontend to analyze the AST and extract developer-defined symbols – including classes, structs, free functions, and member functions. These symbols are then organized under the cxx namespace and emitted as constexpr string identifiers.

The generated sources are compiled and linked statically alongside RTL as part of your build.

Integration is straightforward: include the generated header (cxx_mirror.h) and link against the RTL library. Your project then becomes runtime-reflection ready. You can introspect registered types and invoke functions through RTL’s APIs, with full runtime resolution handled automatically.

Key Features

• ✅ Standard C++ – Generates clean, portable C++20 code.

• ✅ Type-Safe – Compile-time validation of reflection queries.

• ✅ Non-Intrusive – No modifications to your source code required.

Current Status

⚠️ Early Development – Bootstrapping Phase

clang-mirror is actively being built and is not yet ready for general use. In the meantime, you can check out Reflection Template Library (RTL) to explore the underlying runtime reflection system that clang-mirror is designed to support.