Merge pull request #83005 from compnerd/detection

Runtimes: detect the existence of `dispatch_async_swift_job`

Author: compnerd

Runtimes/Core/Concurrency/dispatch.cmake

@@ -1,12 +1,16 @@
 
 find_package(dispatch QUIET REQUIRED)
 
+check_symbol_exists("dispatch_async_swift_job" "dispatch/private.h"
+  SwiftConcurrency_HAS_DISPATCH_ASYNC_SWIFT_JOB)
+
 target_sources(swift_Concurrency PRIVATE
   DispatchGlobalExecutor.cpp
   DispatchExecutor.swift
   CFExecutor.swift
   ExecutorImpl.swift)
 target_compile_definitions(swift_Concurrency PRIVATE
+  $<$<BOOL:${SwiftConcurrency_HAS_DISPATCH_ASYNC_SWIFT_JOB}>:-DSwiftConcurrency_HAS_DISPATCH_ASYNC_SWIFT_JOB=1>
   $<$<COMPILE_LANGUAGE:C,CXX>:-DSWIFT_CONCURRENCY_USES_DISPATCH=1>)
 target_compile_options(swift_Concurrency PRIVATE
   $<$<COMPILE_LANGUAGE:Swift>:-DSWIFT_CONCURRENCY_USES_DISPATCH>

stdlib/public/Concurrency/DispatchGlobalExecutor.cpp

@@ -103,13 +103,15 @@ static void initializeDispatchEnqueueFunc(dispatch_queue_t queue, void *obj,
   if (SWIFT_RUNTIME_WEAK_CHECK(dispatch_async_swift_job))
     func = SWIFT_RUNTIME_WEAK_USE(dispatch_async_swift_job);
 #elif defined(_WIN32)
+#if SwiftConcurrency_HAS_DISPATCH_ASYNC_SWIFT_JOB
 #if defined(dispatch_STATIC)
   func = dispatch_async_swift_job;
 #else
   func = function_cast<dispatchEnqueueFuncType>(
       GetProcAddress(LoadLibraryW(L"dispatch.dll"),
       "dispatch_async_swift_job"));
 #endif
+#endif
 #else
   func = function_cast<dispatchEnqueueFuncType>(
       dlsym(RTLD_NEXT, "dispatch_async_swift_job"));