initial commit

.gitignore

@@ -0,0 +1,6 @@
+/build-*
+/xcode-*
+/.swiftpm
+/.swift
+/.vscode
+/.idea

CMakeLists.txt

@@ -0,0 +1,11 @@
+cmake_minimum_required(VERSION 3.24)
+project(cxxswift LANGUAGES CXX Swift)
+
+set(CMAKE_CXX_STANDARD 20)
+
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
+include(InitializeSwift)
+include(AddSwift)
+
+include_directories("${CMAKE_CURRENT_SOURCE_DIR}/Sources/CppBackend")
+add_subdirectory(Sources)

LICENSE

@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
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+    Copyright 2024 Alex Zenla
+
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+    you may not use this file except in compliance with the License.
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Sources/CMakeLists.txt

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+add_subdirectory(SwiftFrontend)
+add_subdirectory(CppBackend)

Sources/CppBackend/CMakeLists.txt

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+add_library(CppBackend STATIC backend.h backend.cpp)
+
+set_target_properties(CppBackend PROPERTIES Swift_MODULE_NAME "CppBackend")
+target_compile_options(CppBackend PUBLIC "$<$<COMPILE_LANGUAGE:Swift>:-cxx-interoperability-mode=default>")

Sources/CppBackend/backend.cpp

@@ -0,0 +1,7 @@
+#include "backend.h"
+
+#include <iostream>
+
+void backend_init() {
+  std::cout << "Hello World" << std::endl;
+}

Sources/CppBackend/backend.h

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+#pragma once
+
+void backend_init();

Sources/CppBackend/module.modulemap

@@ -0,0 +1,3 @@
+module CppBackend {
+  header "backend.h"
+}

Sources/SwiftFrontend/CMakeLists.txt

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+add_executable(SwiftFrontend main.swift)
+target_link_libraries(SwiftFrontend PRIVATE CppBackend)

Sources/SwiftFrontend/main.swift

@@ -0,0 +1,4 @@
+import CppBackend
+
+backend_init()
+print("Hello World")

cmake/modules/AddSwift.cmake

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+# This source file is part of the Swift open source project
+#
+# Copyright (c) 2023 Apple Inc. and the Swift project authors.
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See https://swift.org/LICENSE.txt for license information
+
+
+# Generate the bridging header from Swift to C++
+#
+# target: the name of the target to generate headers for.
+#         This target must build swift source files.
+# header: the name of the header file to generate.
+#
+# NOTE: This logic will eventually be unstreamed into CMake.
+function(_swift_generate_cxx_header target header)
+  if(NOT TARGET ${target})
+    message(FATAL_ERROR "Target ${target} not defined.")
+  endif()
+
+  if(NOT DEFINED CMAKE_Swift_COMPILER)
+    message(WARNING "Swift not enabled in project. Cannot generate headers for Swift files.")
+    return()
+  endif()
+
+  cmake_parse_arguments(ARG "" "" "SEARCH_PATHS;MODULE_NAME" ${ARGN})
+
+  if(NOT ARG_MODULE_NAME)
+    set(target_module_name $<TARGET_PROPERTY:${target},Swift_MODULE_NAME>)
+    set(ARG_MODULE_NAME $<IF:$<BOOL:${target_module_name}>,${target_module_name},${target}>)
+  endif()
+
+  if(ARG_SEARCH_PATHS)
+    list(TRANSFORM ARG_SEARCH_PATHS PREPEND "-I")
+  endif()
+
+  if(APPLE)
+    set(SDK_FLAGS "-sdk" "${CMAKE_OSX_SYSROOT}")
+  elseif(WIN32)
+    set(SDK_FLAGS "-sdk" "$ENV{SDKROOT}")
+  elseif(DEFINED ${CMAKE_SYSROOT})
+    set(SDK_FLAGS "-sdk" "${CMAKE_SYSROOT}")
+  endif()
+
+  cmake_path(APPEND CMAKE_CURRENT_BINARY_DIR include
+    OUTPUT_VARIABLE base_path)
+
+  cmake_path(APPEND base_path ${header}
+    OUTPUT_VARIABLE header_path)
+
+  set(_AllSources $<TARGET_PROPERTY:${target},SOURCES>)
+  set(_SwiftSources $<FILTER:${_AllSources},INCLUDE,\\.swift$>)
+  add_custom_command(OUTPUT ${header_path}
+    DEPENDS ${_SwiftSources}
+    WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+    COMMAND
+      ${CMAKE_Swift_COMPILER} -frontend -typecheck
+      ${ARG_SEARCH_PATHS}
+      ${_SwiftSources}
+      ${SDK_FLAGS}
+      -module-name "${ARG_MODULE_NAME}"
+      -cxx-interoperability-mode=default
+      -emit-clang-header-path ${header_path}
+    COMMENT
+      "Generating '${header_path}'"
+    COMMAND_EXPAND_LISTS)
+
+  # Added to public interface for dependees to find.
+  target_include_directories(${target} PUBLIC ${base_path})
+  # Added to the target to ensure target rebuilds if header changes and is used
+  # by sources in the target.
+  target_sources(${target} PRIVATE ${header_path})
+endfunction()

cmake/modules/InitializeSwift.cmake

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+# This source file is part of the Swift open source project
+#
+# Copyright (c) 2023 Apple Inc. and the Swift project authors.
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See https://swift.org/LICENSE.txt for license information
+
+# Compute the name of the architecture directory on Windows from the CMake
+# system processor name.
+function(_swift_windows_arch_name output_variable_name target_arch)
+  if(NOT WIN32)
+    return()
+  endif()
+
+  if("${target_arch}" STREQUAL "AMD64")
+    set("${output_variable_name}" "x86_64" PARENT_SCOPE)
+  elseif("${target_arch}" STREQUAL "ARM64")
+    set("${output_variable_name}" "aarch64" PARENT_SCOPE)
+  else()
+    message(FATAL_ERROR "Unknown windows architecture: ${target_arch}")
+  endif()
+endfunction()
+
+# Compute flags and search paths
+# NOTE: This logic will eventually move to CMake
+function(_setup_swift_paths)
+  # If we haven't set the swift library search paths, do that now
+  if(NOT SWIFT_LIBRARY_SEARCH_PATHS)
+    if(APPLE)
+      set(SDK_FLAGS "-sdk" "${CMAKE_OSX_SYSROOT}")
+    endif()
+
+    # Note: This does not handle cross-compiling correctly.
+    #       To handle it correctly, we would need to pass the target triple and
+    #       flags to this compiler invocation.
+    execute_process(
+      COMMAND ${CMAKE_Swift_COMPILER} ${SDK_FLAGS} -print-target-info
+      OUTPUT_VARIABLE SWIFT_TARGET_INFO
+    )
+
+    # extract search paths from swift driver response
+    string(JSON SWIFT_TARGET_PATHS GET ${SWIFT_TARGET_INFO} "paths")
+
+    string(JSON SWIFT_TARGET_LIBRARY_PATHS GET ${SWIFT_TARGET_PATHS} "runtimeLibraryPaths")
+    string(JSON SWIFT_TARGET_LIBRARY_PATHS_LENGTH LENGTH ${SWIFT_TARGET_LIBRARY_PATHS})
+    math(EXPR SWIFT_TARGET_LIBRARY_PATHS_LENGTH "${SWIFT_TARGET_LIBRARY_PATHS_LENGTH} - 1 ")
+
+    string(JSON SWIFT_TARGET_LIBRARY_IMPORT_PATHS GET ${SWIFT_TARGET_PATHS} "runtimeLibraryImportPaths")
+    string(JSON SWIFT_TARGET_LIBRARY_IMPORT_PATHS_LENGTH LENGTH ${SWIFT_TARGET_LIBRARY_IMPORT_PATHS})
+    math(EXPR SWIFT_TARGET_LIBRARY_IMPORT_PATHS_LENGTH "${SWIFT_TARGET_LIBRARY_IMPORT_PATHS_LENGTH} - 1 ")
+
+    string(JSON SWIFT_SDK_IMPORT_PATH ERROR_VARIABLE errno GET ${SWIFT_TARGET_PATHS} "sdkPath")
+
+    foreach(JSON_ARG_IDX RANGE ${SWIFT_TARGET_LIBRARY_PATHS_LENGTH})
+      string(JSON SWIFT_LIB GET ${SWIFT_TARGET_LIBRARY_PATHS} ${JSON_ARG_IDX})
+      list(APPEND SWIFT_SEARCH_PATHS ${SWIFT_LIB})
+    endforeach()
+
+    foreach(JSON_ARG_IDX RANGE ${SWIFT_TARGET_LIBRARY_IMPORT_PATHS_LENGTH})
+      string(JSON SWIFT_LIB GET ${SWIFT_TARGET_LIBRARY_IMPORT_PATHS} ${JSON_ARG_IDX})
+      list(APPEND SWIFT_SEARCH_PATHS ${SWIFT_LIB})
+    endforeach()
+
+    if(SWIFT_SDK_IMPORT_PATH)
+      list(APPEND SWIFT_SEARCH_PATHS ${SWIFT_SDK_IMPORT_PATH})
+    endif()
+
+    # Save the swift library search paths
+    set(SWIFT_LIBRARY_SEARCH_PATHS ${SWIFT_SEARCH_PATHS} CACHE FILEPATH "Swift driver search paths")
+  endif()
+
+  link_directories(${SWIFT_LIBRARY_SEARCH_PATHS})
+
+  if(WIN32)
+    _swift_windows_arch_name(SWIFT_WIN_ARCH_DIR "${CMAKE_SYSTEM_PROCESSOR}")
+    set(SWIFT_SWIFTRT_FILE "$ENV{SDKROOT}/usr/lib/swift/windows/${SWIFT_WIN_ARCH_DIR}/swiftrt.obj")
+    add_link_options("$<$<LINK_LANGUAGE:Swift>:${SWIFT_SWIFTRT_FILE}>")
+  elseif(NOT APPLE)
+    find_file(SWIFT_SWIFTRT_FILE
+              swiftrt.o
+              PATHS ${SWIFT_LIBRARY_SEARCH_PATHS}
+              NO_CACHE
+              REQUIRED
+              NO_DEFAULT_PATH)
+    add_link_options("$<$<LINK_LANGUAGE:Swift>:${SWIFT_SWIFTRT_FILE}>")
+  endif()
+endfunction()
+
+_setup_swift_paths()