Android Pure C++ Turbo Module Static & Shared Library

[Zach-Dean-Attractions-io]

In this repository I have a library which implements a pure C++ Turbo Module.

The Android CMakeLists.txt file looks like so

cmake_minimum_required(VERSION 3.4.1)
project(PureCppTurboModuleLibrary)

set (CMAKE_VERBOSE_MAKEFILE ON)

add_library(
    pure-cpp-turbo-module-library
    STATIC
    ../cpp/PureCppImpl.cpp
)

# Specifies a path to native header files.
target_include_directories(
    pure-cpp-turbo-module-library
    PUBLIC
    ../cpp
)

target_link_libraries(
    pure-cpp-turbo-module-library
    jsi
    reactnative
    react_codegen_RNPureCppTurboModuleLibrarySpec
)

However, I want the ability to call from Java back into C++ and then call a method say in PureCppImpl.cpp. To call into C++ from Java I need to use a SHARED library instead of a STATIC library. I planned to create a new SHARED library alongside this STATIC library, which would have a C++ file that imports the PureCppImpl.h file. However, this SHARED library isn't simple to set up due to a lot of missing include directories.

To illustrate this, if I change the add_library statement to the following

add_library(
    pure-cpp-turbo-module-library
-    STATIC
+    SHARED
    ../cpp/PureCppImpl.cpp
)

Then I get an error here that <RNPureCppTurboModuleLibrarySpecJSI.h> can not be found. If I then update the target_include_directories to include that file

target_include_directories(
   pure-cpp-turbo-module-library
   PUBLIC
   ../cpp
+  generated/jni/react/renderer/components/RNPureCppTurboModuleLibrarySpec
)

Then I get an error in the file RNPureCppTurboModuleLibrarySpecJSI.h that the file 'ReactCommon/TurboModule.h' can not be found. So I then add this into the target_include_directories

target_include_directories(
   pure-cpp-turbo-module-library
   PUBLIC
   ../cpp
  generated/jni/react/renderer/components/RNPureCppTurboModuleLibrarySpec
+ ${CMAKE_CURRENT_SOURCE_DIR}/../node_modules/react-native/ReactCommon/react/nativemodule/core
)

I then get another error for #include <jsi/jsi.h>.

I've been carrying on in this way with the SHARED library but I run into a lot of issues. In my case because the SHARED library I have needs to call into a file in the STATIC library, I think (but not fully sure) that when the shared library is compiled that it doesn't have all the include statements that for some reason (I'm not sure why) I get for free with the static library. Although once I have the shared library that depends on the static library it seems to break the static library too. At some point it even fails with the error that the library react_codegen_RNPureCppTurboModuleLibrarySpec can't be found and so I had to remove the generated CMakeLists.txt file that creates that library and define it myself. However, even after this I ran into issues with the import <folly/dynamic.h> which I couldn't solve.

Is there an easier way to do this?

I can provide a full example of what I am trying to achieve by calling from C++ into Java and then back into C++ if that will help.

[cortinico]

To call into C++ from Java I need to use a SHARED library instead of a STATIC library.

That's not correct. You can use either a SHARED or a STATIC library to achieve what you're trying to do .

I can provide a full example of what I am trying to achieve by calling from C++ into Java and then back into C++ if that will help.

That would help. If you could use this template: https://github.com/react-native-community/reproducer-react-native we could look into it

[Zach-Dean-Attractions-io]

I've created a sample here. It's not the best code but it illustrates the point.

However, in the sample project based upon the reproducer, the ReactNative-application.cmake you need to include (as per the docs here) builds the C++ library as a shared library and so I can call into it from Java and the sample project shows that.

Therefore, the problem I have is more so how to build a library project including a pure C++ turbo module. This repository here demonstrated the code I needed to get it working. It defines the C++ library as STATIC though in the cmake file. If I change this to be SHARED then I get into the issue where it can't find any of the import header paths. I can only assume that when it is built as STATIC the library inherits a bunch of import header paths, which doesn't happen when it is SHARED. If you clone this repo then it will build successfully but then if you change the library from STATIC to SHARED then it causes a lot of issues I don't know how best to resolve.