runtime cxx module autolinking

[philIip]

Summary:

Changelog: [iOS][Android][Added] Experimental macro to autolink C++ turbomodules

this implementation is inspired by RCT_EXPORT_MODULE, we keep a global data structure that maps module names to a lambda that returns the C++ turbomodule. this will come with a hit to startup time. the only way to avoid that is a codegen solution. this is an experimental solution because we don't have a proper autolinking solution for ios modules that doesn't require changes in the app layer.

How to use

In the .cpp file of your TurboModule, add the following line, where MyCxxNativeModule is the identifier of your module. This will automatically link the module on both iOS and Android. The class name of your TurboModule must match its JavaScript module identifier and live in the facebook::react namespace.

#include <ReactCommon/CxxTurboModuleUtils.h>

RCT_EXPORT_CXX_MODULE_EXPERIMENTAL(MyCxxNativeModule)

namespace facebook::react {
  	
MyCxxNativeModule::MyCxxNativeModule(
...

there's still a catch here, because the macro can still get compiled out if the compiler thinks the file is not being used. this is how you can work around this at the build level:

on android, in your CMakeLists.txt, pass in -Wl, --whole_archive to add_compile_options .

add_compile_options(-Wl, --whole_archive)

on iOS, in the podspec, pass "-Wl, --whole_archive" as the value to "OTHER_LDFLAGS" in the pod_target_xcconfig.

Pod::Spec.new do |s|
  ...
  s.pod_target_xcconfig = {
    "OTHER_LDFLAGS" => "-Wl, --whole_archive"
  }
  ...
end

Differential Revision: D53602544

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D53602544

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D53602544

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	17,832,418	+4,083
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	21,190,890	+4,094
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: e4135e9
Branch: main

[facebook-github-bot]

This pull request has been merged in 01d704d.

[jpudysz]

Hey @philIip!

I've tried your macro on iOS and confirmed that I added the compiler flags. I'm also using the same name in JS, but my module can't be registered. What works for me is the Obj-C macro with the load method:

#define INIT_CXX_MODULE(NAME) \
    @interface CxxModule: NSObject \
    @end \
    @implementation CxxModule \
    + (void)load { \
        facebook::react::registerCxxModuleToGlobalModuleMap( \
            std::string(facebook::react::NAME::kModuleName), \
            [](std::shared_ptr<facebook::react::CallInvoker> jsInvoker){ \
                return std::make_shared<facebook::react::NAME>(jsInvoker); \
            } \
        ); \
    } \
    @end \

It seems like the C++ code is never executed and the module is not registered. Can you give me any hints on how to handle this? It would be perfect to initialize my C++ TurboModule from C++ without single Obj-C file.
By the way, I'm using Codegen too.