From a332b7b782315c9408192d4c6ee4167fb81459e8 Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <abdulras@thebrowser.company>
Date: Wed, 3 Jul 2024 08:37:19 -0700
Subject: [PATCH 1/2] FoundationMacros: use cross-compilation to build for host

Use `ExternalProject` to switch FoundationMacros to cross-compilation.
This allows us to build the macros for the right OS/architecture when
cross-compiling Foundation for other environments.
---
 Sources/CMakeLists.txt                  | 25 ++++++++++++++++++++-----
 Sources/FoundationMacros/CMakeLists.txt | 17 ++++++++++++++++-
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/Sources/CMakeLists.txt b/Sources/CMakeLists.txt
index f7f7ba156..fa411c6d1 100644
--- a/Sources/CMakeLists.txt
+++ b/Sources/CMakeLists.txt
@@ -12,12 +12,27 @@
 ##
 ##===----------------------------------------------------------------------===##
 
-add_subdirectory(_FoundationCShims)
-
-# Disable the macro build on Windows until we can correctly build it for the host architecture
-if(NOT CMAKE_SYSTEM_NAME STREQUAL Windows)
-	add_subdirectory(FoundationMacros)
+include(ExternalProject)
+if(CMAKE_HOST_WIN32)
+  set(_FoundationMacrosSwiftFlags -DCMAKE_Swift_FLAGS="-use-ld=lld")
+endif()
+ExternalProject_Add(FoundationMacros
+  SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/FoundationMacros"
+  PREFIX "${CMAKE_BINARY_DIR}/_deps"
+  BINARY_DIR "macros"
+  CMAKE_ARGS
+    -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
+    ${_FoundationMacrosSwiftFlags}
+  INSTALL_COMMAND "")
+ExternalProject_Get_Property(FoundationMacros BINARY_DIR)
+if(CMAKE_HOST_WIN32)
+  set(_SwiftFoundation_PredicateMacro "${BINARY_DIR}/FoundationMacros.exe#PredicateMacro")
+  set(_SwiftFoundation_ExpressionMacro "${BINARY_DIR}/FoundationMacros.exe#ExpressionMacro")
+else()
+  set(_SwiftFoundation_PredicateMacro "${BINARY_DIR}/FoundationMacros#PredicateMacro")
+  set(_SwiftFoundation_ExpressionMacro "${BINARY_DIR}/FoundationMacros#ExpressionMacro")
 endif()
 
+add_subdirectory(_FoundationCShims)
 add_subdirectory(FoundationEssentials)
 add_subdirectory(FoundationInternationalization)
diff --git a/Sources/FoundationMacros/CMakeLists.txt b/Sources/FoundationMacros/CMakeLists.txt
index bbc7bd628..239dd6c44 100644
--- a/Sources/FoundationMacros/CMakeLists.txt
+++ b/Sources/FoundationMacros/CMakeLists.txt
@@ -12,10 +12,25 @@
 ##
 ##===----------------------------------------------------------------------===##
 
+cmake_minimum_required(VERSION 3.22)
+
+if(POLICY CMP0156)
+    # Deduplicate linked libraries where appropriate
+    cmake_policy(SET CMP0156 NEW)
+endif()
+if(POLICY CMP0157)
+    # New Swift build model: improved incremental build performance and LSP support
+  cmake_policy(SET CMP0157 NEW)
+endif()
+
+project(FoundationMacros
+  LANGUAGES Swift)
+
 # SwiftSyntax Dependency
-include(FetchContent)
 find_package(SwiftSyntax)
 if(NOT SwiftSyntax_FOUND)
+    include(FetchContent)
+
     # If building at desk, check out and link against the SwiftSyntax repo's targets
     FetchContent_Declare(SwiftSyntax
         GIT_REPOSITORY https://github.com/swiftlang/swift-syntax.git

From 7baf52b445cd9c8b22525ea47a85501300af5fbc Mon Sep 17 00:00:00 2001
From: Alex Lorenz <arphaman@gmail.com>
Date: Mon, 29 Jul 2024 12:26:29 -0700
Subject: [PATCH 2/2] [macros] pass in additional CMAKE_HOST_Swift_FLAGS when
 building foundation macros on a windows host, when such flags are present

---
 Sources/CMakeLists.txt | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Sources/CMakeLists.txt b/Sources/CMakeLists.txt
index fa411c6d1..ad8ecf178 100644
--- a/Sources/CMakeLists.txt
+++ b/Sources/CMakeLists.txt
@@ -14,7 +14,11 @@
 
 include(ExternalProject)
 if(CMAKE_HOST_WIN32)
-  set(_FoundationMacrosSwiftFlags -DCMAKE_Swift_FLAGS="-use-ld=lld")
+  set(_flags "-use-ld=lld")
+  if(DEFINED CMAKE_HOST_Swift_FLAGS)
+    set(_flags "${_flags} ${CMAKE_HOST_Swift_FLAGS}")
+  endif()
+  set(_FoundationMacrosSwiftFlags "-DCMAKE_Swift_FLAGS=${_flags}")
 endif()
 ExternalProject_Add(FoundationMacros
   SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/FoundationMacros"