Introduce SWIFT_FREESTANDING_FLAVOR to select whether the FREESTANDING stdlib should be built/tested using an Apple SDK, or another SDK (e.g. Linux, not implemented yet)

CMakeLists.txt

@@ -744,6 +744,12 @@ if("${SWIFT_HOST_VARIANT_SDK}" STREQUAL "LINUX")
     set(SWIFT_PRIMARY_VARIANT_ARCH_default "${SWIFT_HOST_VARIANT_ARCH}")
   endif()
 
+  is_sdk_requested(FREESTANDING swift_build_freestanding)
+  if(swift_build_freestanding AND (SWIFT_FREESTANDING_FLAVOR STREQUAL "linux"))
+    # TODO
+    # configure_sdk_unix("FREESTANDING" "${SWIFT_HOST_VARIANT_ARCH}")
+  endif()
+
 elseif("${SWIFT_HOST_VARIANT_SDK}" STREQUAL "FREEBSD")
 
   set(SWIFT_HOST_VARIANT "freebsd" CACHE STRING

cmake/modules/DarwinSDKs.cmake

@@ -27,7 +27,7 @@ if(swift_build_osx)
 endif()
 
 is_sdk_requested(FREESTANDING swift_build_freestanding)
-if(swift_build_freestanding)
+if(swift_build_freestanding AND (SWIFT_FREESTANDING_FLAVOR STREQUAL "apple"))
   set(SWIFT_FREESTANDING_SDK "" CACHE STRING
       "Which SDK to use when building the FREESTANDING stdlib")
   set(SWIFT_FREESTANDING_TRIPLE_NAME "" CACHE STRING
@@ -45,6 +45,8 @@ if(swift_build_freestanding)
   configure_target_variant(FREESTANDING-RA "FREESTANDING Release+Asserts" FREESTANDING RA "Release+Asserts")
   configure_target_variant(FREESTANDING-R  "FREESTANDING Release"         FREESTANDING R  "Release")
   configure_target_variant(FREESTANDING-S  "FREESTANDING MinSizeRelease"  FREESTANDING S  "MinSizeRelease")
+
+  set(SWIFT_FREESTANDING_TEST_DEPENDENCIES "Darwin")
 endif()
 
 # Compatible cross-compile SDKS for Darwin OSes: IOS, IOS_SIMULATOR, TVOS,

stdlib/CMakeLists.txt

@@ -79,6 +79,9 @@ option(SWIFT_BUILD_TEST_SUPPORT_MODULES
        "Whether to build StdlibUnittest and other test support modules. Defaults to On when SWIFT_BUILD_SDK_OVERLAY is On, or when SWIFT_INCLUDE_TESTS is On."
        "${SWIFT_BUILD_TEST_SUPPORT_MODULES_default}")
 
+option(SWIFT_FREESTANDING_FLAVOR
+       "When building the FREESTANDING stdlib, which build style to use (options: apple, linux)")
+
 set(SWIFT_STDLIB_ENABLE_LTO OFF CACHE STRING "Build Swift stdlib with LTO. One
     must specify the form of LTO by setting this to one of: 'full', 'thin'. This
     option only affects the standard library and runtime, not tools.")

stdlib/private/StdlibUnittest/CMakeLists.txt

@@ -46,7 +46,7 @@ add_swift_target_library(swiftStdlibUnittest ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES}
   SWIFT_MODULE_DEPENDS_OSX Darwin
   SWIFT_MODULE_DEPENDS_TVOS Darwin
   SWIFT_MODULE_DEPENDS_WATCHOS Darwin
-  SWIFT_MODULE_DEPENDS_FREESTANDING Darwin
+  SWIFT_MODULE_DEPENDS_FREESTANDING "${SWIFT_FREESTANDING_TEST_DEPENDENCIES}"
   SWIFT_MODULE_DEPENDS_LINUX Glibc
   SWIFT_MODULE_DEPENDS_FREEBSD Glibc
   SWIFT_MODULE_DEPENDS_OPENBSD Glibc

stdlib/private/SwiftPrivateLibcExtras/CMakeLists.txt

@@ -13,7 +13,7 @@ add_swift_target_library(swiftSwiftPrivateLibcExtras ${SWIFT_STDLIB_LIBRARY_BUIL
   SWIFT_MODULE_DEPENDS_IOS Darwin
   SWIFT_MODULE_DEPENDS_TVOS Darwin
   SWIFT_MODULE_DEPENDS_WATCHOS Darwin
-  SWIFT_MODULE_DEPENDS_FREESTANDING Darwin
+  SWIFT_MODULE_DEPENDS_FREESTANDING "${SWIFT_FREESTANDING_TEST_DEPENDENCIES}"
   SWIFT_MODULE_DEPENDS_LINUX Glibc
   SWIFT_MODULE_DEPENDS_FREEBSD Glibc
   SWIFT_MODULE_DEPENDS_OPENBSD Glibc

stdlib/private/SwiftPrivateThreadExtras/CMakeLists.txt

@@ -10,7 +10,7 @@ add_swift_target_library(swiftSwiftPrivateThreadExtras ${SWIFT_STDLIB_LIBRARY_BU
   SWIFT_MODULE_DEPENDS_OSX Darwin
   SWIFT_MODULE_DEPENDS_TVOS Darwin
   SWIFT_MODULE_DEPENDS_WATCHOS Darwin
-  SWIFT_MODULE_DEPENDS_FREESTANDING Darwin
+  SWIFT_MODULE_DEPENDS_FREESTANDING "${SWIFT_FREESTANDING_TEST_DEPENDENCIES}"
   SWIFT_MODULE_DEPENDS_LINUX Glibc
   SWIFT_MODULE_DEPENDS_FREEBSD Glibc
   SWIFT_MODULE_DEPENDS_OPENBSD Glibc

stdlib/public/Platform/CMakeLists.txt

@@ -11,6 +11,10 @@ if(NOT BUILD_STANDALONE)
   list(APPEND darwin_depends copy_apinotes)
 endif()
 
+set(swiftDarwin_target_sdks ALL_APPLE_PLATFORMS)
+if(SWIFT_FREESTANDING_FLAVOR STREQUAL "apple")
+  set(swiftDarwin_target_sdks ALL_APPLE_PLATFORMS FREESTANDING)
+endif()
 add_swift_target_library(swiftDarwin ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_SDK_OVERLAY
     ${swift_platform_sources}
     POSIXError.swift
@@ -27,11 +31,15 @@ add_swift_target_library(swiftDarwin ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_SDK_
       ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
       -Xfrontend -disable-objc-attr-requires-foundation-module
     LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
-    TARGET_SDKS ALL_APPLE_PLATFORMS FREESTANDING
+    TARGET_SDKS "${swiftDarwin_target_sdks}"
     INSTALL_IN_COMPONENT sdk-overlay
 
     DEPENDS ${darwin_depends})
 
+set(swiftGlibc_target_sdks ANDROID CYGWIN FREEBSD OPENBSD LINUX HAIKU)
+if(SWIFT_FREESTANDING_FLAVOR STREQUAL "linux")
+  set(swiftGlibc_target_sdks ANDROID CYGWIN FREEBSD OPENBSD LINUX HAIKU FREESTANDING)
+endif()
 add_swift_target_library(swiftGlibc ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_SDK_OVERLAY
     ${swift_platform_sources}
     POSIXError.swift
@@ -44,7 +52,7 @@ add_swift_target_library(swiftGlibc ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_SDK_O
       ${SWIFT_RUNTIME_SWIFT_COMPILE_FLAGS}
       ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
     LINK_FLAGS "${SWIFT_RUNTIME_SWIFT_LINK_FLAGS}"
-    TARGET_SDKS ANDROID CYGWIN FREEBSD OPENBSD LINUX HAIKU
+    TARGET_SDKS "${swiftGlibc_target_sdks}"
     INSTALL_IN_COMPONENT sdk-overlay
     DEPENDS glibc_modulemap)
 

utils/build-presets.ini

@@ -2442,6 +2442,7 @@ mixin-preset=
 stdlib-deployment-targets=freestanding-x86_64
 swift-primary-variant-sdk=FREESTANDING
 swift-primary-variant-arch=x86_64
+swift-freestanding-flavor=apple
 swift-freestanding-sdk=macosx
 # For now, until clang/swiftc works correctly with "none-macho" as the OS part of target triple.
 swift-freestanding-triple-name=macosx11.0

utils/build-script-impl

@@ -207,10 +207,11 @@ KNOWN_SETTINGS=(
     common-swift-flags                            ""                "Flags used for Swift targets other than the stdlib, like the corelibs"
 
     ## FREESTANDING Stdlib Options
-    swift-freestanding-sdk                      ""                "which SDK to use when building the FREESTANDING stdlib"
-    swift-freestanding-triple-name              ""                "which triple name (e.g. 'none-macho') to use when building the FREESTANDING stdlib"
-    swift-freestanding-module-name              ""                "which .swiftmodule name (e.g. 'freestanding') to use when building the FREESTANDING stdlib"
-    swift-freestanding-archs                    ""                "space-separated list of which architectures to build when building the FREESTANDING stdlib"
+    swift-freestanding-flavor                     ""                "when building the FREESTANDING stdlib, which build style to use (options: apple, linux)"
+    swift-freestanding-sdk                        ""                "which SDK to use when building the FREESTANDING stdlib"
+    swift-freestanding-triple-name                ""                "which triple name (e.g. 'none-macho') to use when building the FREESTANDING stdlib"
+    swift-freestanding-module-name                ""                "which .swiftmodule name (e.g. 'freestanding') to use when building the FREESTANDING stdlib"
+    swift-freestanding-archs                      ""                "space-separated list of which architectures to build when building the FREESTANDING stdlib"
 
     ## Uncategorised
     install-prefix                                ""                "installation prefix"
@@ -2072,6 +2073,13 @@ for host in "${ALL_HOSTS[@]}"; do
                     )
                 fi
 
+                if [ "${SWIFT_FREESTANDING_FLAVOR}" ] ; then
+                    cmake_options=(
+                        "${cmake_options[@]}"
+                        -DSWIFT_FREESTANDING_FLAVOR:STRING="${SWIFT_FREESTANDING_FLAVOR}"
+                    )
+                fi
+
                 if [ "${SWIFT_FREESTANDING_SDK}" ] ; then
                     cmake_options=(
                         "${cmake_options[@]}"