Enable -experimental-hermetic-seal-at-link for the stdlib on 'freestanding' (#39961)

Author: kubamracek

stdlib/CMakeLists.txt

@@ -143,9 +143,13 @@ option(SWIFT_FREESTANDING_FLAVOR
        "When building the FREESTANDING stdlib, which build style to use (options: apple, linux)")
 
 option(SWIFT_STDLIB_ENABLE_PRESPECIALIZATION
-       "Should stdlib be built with generic metadata prespecialization enabled. Defaults to On on Darwin and on "
+       "Should stdlib be built with generic metadata prespecialization enabled. Defaults to On on Darwin and on Linux."
        "${SWIFT_STDLIB_ENABLE_PRESPECIALIZATION_default}")
 
+option(SWIFT_STDLIB_EXPERIMENTAL_HERMETIC_SEAL_AT_LINK
+       "Should stdlib be built with -experimental-hermetic-seal-at-link"
+       FALSE)
+
 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/cmake/modules/SwiftSource.cmake

@@ -502,6 +502,10 @@ function(_compile_swift_files
     list(APPEND swift_flags "-Xfrontend" "-disable-objc-interop")
   endif()
 
+  if(SWIFT_STDLIB_EXPERIMENTAL_HERMETIC_SEAL_AT_LINK)
+    list(APPEND swift_flags "-experimental-hermetic-seal-at-link")
+  endif()
+
   list(APPEND swift_flags ${SWIFT_EXPERIMENTAL_EXTRA_FLAGS})
 
   if(SWIFTFILE_OPT_FLAGS)

test/lit.cfg

@@ -950,6 +950,8 @@ if run_vendor == 'apple':
         # it's a very desired behavior, let's enable it for all executable tests.
         swift_execution_tests_extra_flags += ' -Xlinker -dead_strip'
 
+        swift_execution_tests_extra_flags += ' -experimental-hermetic-seal-at-link -lto=llvm-full'
+
         # Build a resource dir for freestanding tests.
         new_resource_dir = os.path.join(config.test_exec_root, "resource_dir")
         if not os.path.exists(new_resource_dir): os.mkdir(new_resource_dir)

test/stdlib/KeyPathMultiModule.swift

@@ -15,6 +15,9 @@
 
 // REQUIRES: executable_test
 
+// Freestanding stdlib is built with -experimental-hermetic-seal-at-link which doesn't allow -enable-library-evolution
+// UNSUPPORTED: freestanding
+
 import KeyPathMultiModule_b
 import StdlibUnittest
 

utils/build-presets.ini

@@ -2493,6 +2493,7 @@ extra-cmake-options=
     -DSWIFT_STDLIB_ENABLE_PRESPECIALIZATION:BOOL=FALSE
     -DSWIFT_STDLIB_PASSTHROUGH_METADATA_ALLOCATOR:BOOL=TRUE
     -DSWIFT_STDLIB_SHORT_MANGLING_LOOKUPS:BOOL=FALSE
+    -DSWIFT_STDLIB_EXPERIMENTAL_HERMETIC_SEAL_AT_LINK:BOOL=TRUE
 
 [preset: stdlib_S_standalone_minimal_macho_x86_64,build]
 mixin-preset=