feat: add support for optional FFI AST export with clang++

Author: Katze719

CMakeLists.txt

@@ -11,6 +11,20 @@ set(CMAKE_CXX_EXTENSIONS OFF)
 set(CMAKE_CXX_MODULE_STD 26)
 set(CMAKE_CXX_MODULE_EXTENSIONS OFF)
 
+option(CPP_CORE_ENABLE_AST_EXPORT "Enable clang-based JSON AST export for the FFI headers" ON)
+set(
+    CPP_CORE_AST_JSON_OUTPUT
+    "${CMAKE_BINARY_DIR}/ast/cpp_core_ffi_ast.json"
+    CACHE FILEPATH
+    "Output path for the generated FFI AST JSON file"
+)
+set(
+    CPP_CORE_AST_CLANGXX
+    ""
+    CACHE FILEPATH
+    "Path to the clang++ executable used for AST JSON export"
+)
+
 if(NOT CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     message(FATAL_ERROR "cpp-core currently requires GCC 16.1+ with the GCC std::meta reflection implementation.")
 endif()
@@ -77,6 +91,64 @@ if(BUILD_TESTING)
     target_link_libraries(cpp_core_compile_tests PRIVATE cpp_core_strict_warnings)
 endif()
 
+if(CPP_CORE_ENABLE_AST_EXPORT)
+    file(
+        GLOB _cpp_core_ast_interface_headers
+        CONFIGURE_DEPENDS
+        "${CMAKE_CURRENT_SOURCE_DIR}/include/cpp_core/interface/*.h"
+    )
+
+    set(
+        _cpp_core_ast_headers
+        "${CMAKE_CURRENT_SOURCE_DIR}/include/cpp_core/serial.h"
+        "${CMAKE_CURRENT_SOURCE_DIR}/include/cpp_core/error_callback.h"
+        "${CMAKE_CURRENT_SOURCE_DIR}/include/cpp_core/module_api.h"
+        "${CMAKE_CURRENT_SOURCE_DIR}/include/cpp_core/version.hpp"
+        ${_cpp_core_ast_interface_headers}
+    )
+
+    if(CPP_CORE_AST_CLANGXX)
+        set(_cpp_core_ast_clangxx "${CPP_CORE_AST_CLANGXX}")
+    else()
+        find_program(_cpp_core_ast_clangxx NAMES clang++)
+    endif()
+
+    if(NOT _cpp_core_ast_clangxx)
+        message(
+            FATAL_ERROR
+            "CPP_CORE_ENABLE_AST_EXPORT=ON requires clang++. "
+            "Install clang++ or set CPP_CORE_AST_CLANGXX to an explicit path."
+        )
+    endif()
+
+    set(_cpp_core_ast_wrapper "${CMAKE_CURRENT_BINARY_DIR}/ast/cpp_core_ffi_ast.cpp")
+    get_filename_component(_cpp_core_ast_json_dir "${CPP_CORE_AST_JSON_OUTPUT}" DIRECTORY)
+
+    file(
+        GENERATE
+        OUTPUT "${_cpp_core_ast_wrapper}"
+        CONTENT "#include <cpp_core/serial.h>\n"
+    )
+
+    add_custom_command(
+        OUTPUT "${CPP_CORE_AST_JSON_OUTPUT}"
+        COMMAND ${CMAKE_COMMAND} -E make_directory "${_cpp_core_ast_json_dir}"
+        COMMAND
+            ${CMAKE_COMMAND}
+            -DCPP_CORE_AST_CLANGXX=${_cpp_core_ast_clangxx}
+            -DCPP_CORE_AST_INCLUDE_DIR=${CMAKE_CURRENT_SOURCE_DIR}/include
+            -DCPP_CORE_AST_OUTPUT=${CPP_CORE_AST_JSON_OUTPUT}
+            -DCPP_CORE_AST_SOURCE=${_cpp_core_ast_wrapper}
+            -DCPP_CORE_AST_STANDARD=${CMAKE_CXX_STANDARD}
+            -P ${CMAKE_CURRENT_SOURCE_DIR}/cmake/export_ast_json.cmake
+        DEPENDS "${_cpp_core_ast_wrapper}" ${_cpp_core_ast_headers}
+        COMMENT "Exporting FFI header AST JSON with clang++"
+        VERBATIM
+    )
+
+    add_custom_target(cpp_core_ast_json DEPENDS "${CPP_CORE_AST_JSON_OUTPUT}")
+endif()
+
 # Install rules --------------------------------------------------------------
 include(GNUInstallDirs)
 

README.md

@@ -86,6 +86,18 @@ The CMake project exports the package target and also builds these relevant targ
 - `cpp_core::cpp_core`: header-only interface target
 - `cpp_core_compile_tests`: compile-time validation target when testing is enabled
 
+Optional FFI AST export:
+
+```sh
+cmake -S . -B build -G Ninja -DCMAKE_TOOLCHAIN_FILE=cmake/gcc-toolchain.cmake -DCPP_CORE_ENABLE_AST_EXPORT=ON
+cmake --build build --target cpp_core_ast_json
+```
+
+- The project still configures with GCC; the AST export itself invokes `clang++` separately
+- Requires `clang++` on `PATH` or `-DCPP_CORE_AST_CLANGXX=/path/to/clang++`
+- Writes the combined FFI header AST JSON to `build/ast/cpp_core_ffi_ast.json`
+- Exports the `#include <cpp_core/serial.h>` surface intended for downstream FFI adapter generation
+
 ## ABI Surface
 
 The main aggregated interface lives in:

cmake/export_ast_json.cmake

@@ -0,0 +1,50 @@
+cmake_minimum_required(VERSION 3.30)
+
+foreach(required_var
+        CPP_CORE_AST_CLANGXX
+        CPP_CORE_AST_INCLUDE_DIR
+        CPP_CORE_AST_OUTPUT
+        CPP_CORE_AST_SOURCE
+        CPP_CORE_AST_STANDARD)
+    if(NOT DEFINED ${required_var} OR "${${required_var}}" STREQUAL "")
+        message(FATAL_ERROR "Missing required variable: ${required_var}")
+    endif()
+endforeach()
+
+get_filename_component(_cpp_core_ast_output_dir "${CPP_CORE_AST_OUTPUT}" DIRECTORY)
+file(MAKE_DIRECTORY "${_cpp_core_ast_output_dir}")
+
+execute_process(
+    COMMAND
+        "${CMAKE_COMMAND}" -E env
+        CCACHE_DISABLE=1
+        "${CPP_CORE_AST_CLANGXX}"
+        "-std=c++${CPP_CORE_AST_STANDARD}"
+        "-I${CPP_CORE_AST_INCLUDE_DIR}"
+        -fsyntax-only
+        -Xclang
+        -ast-dump=json
+        "${CPP_CORE_AST_SOURCE}"
+    OUTPUT_FILE "${CPP_CORE_AST_OUTPUT}"
+    ERROR_VARIABLE _cpp_core_ast_stderr
+    RESULT_VARIABLE _cpp_core_ast_result
+)
+
+if(NOT _cpp_core_ast_result EQUAL 0)
+    file(REMOVE "${CPP_CORE_AST_OUTPUT}")
+    string(STRIP "${_cpp_core_ast_stderr}" _cpp_core_ast_stderr)
+    message(
+        FATAL_ERROR
+        "clang AST export failed with exit code ${_cpp_core_ast_result}.\n${_cpp_core_ast_stderr}"
+    )
+endif()
+
+if(NOT EXISTS "${CPP_CORE_AST_OUTPUT}")
+    message(FATAL_ERROR "clang AST export did not produce ${CPP_CORE_AST_OUTPUT}")
+endif()
+
+file(SIZE "${CPP_CORE_AST_OUTPUT}" _cpp_core_ast_size)
+if(_cpp_core_ast_size EQUAL 0)
+    file(REMOVE "${CPP_CORE_AST_OUTPUT}")
+    message(FATAL_ERROR "clang AST export produced an empty file: ${CPP_CORE_AST_OUTPUT}")
+endif()