[Concurrency] Add availability checking when calling voucher_needs_adopt from the SDK.

Author: mikeash

include/swift/Runtime/VoucherShims.h

@@ -39,8 +39,18 @@
 
 #if SWIFT_HAS_VOUCHERS
 
+#if SWIFT_HAS_VOUCHER_HEADER
+
+static inline bool swift_voucher_needs_adopt(voucher_t _Nullable voucher) {
+  if (__builtin_available(macOS 12.0, iOS 15.0, tvOS 15.0, watchOS 8.0, *)) {
+    return voucher_needs_adopt(voucher);
+  }
+  return true;
+}
+
+#else
+
 // If the header isn't available, declare the necessary calls here.
-#if !SWIFT_HAS_VOUCHER_HEADER
 
 #include <os/object.h>
 
@@ -54,7 +64,7 @@ extern "C" voucher_t _Nullable voucher_copy(void);
 // Consumes argument, returns retained value.
 extern "C" voucher_t _Nullable voucher_adopt(voucher_t _Nullable voucher);
 
-static inline bool voucher_needs_adopt(voucher_t _Nullable voucher) {
+static inline bool swift_voucher_needs_adopt(voucher_t _Nullable voucher) {
   return true;
 }
 
@@ -78,7 +88,7 @@ static inline voucher_t _Nullable voucher_copy(void) { return nullptr; }
 static inline voucher_t _Nullable voucher_adopt(voucher_t _Nullable voucher) {
   return nullptr;
 }
-static inline bool voucher_needs_adopt(voucher_t _Nullable voucher) {
+static inline bool swift_voucher_needs_adopt(voucher_t _Nullable voucher) {
   return true;
 }
 static inline void swift_voucher_release(voucher_t _Nullable voucher) {}

stdlib/public/Concurrency/VoucherSupport.h

@@ -44,7 +44,7 @@ class VoucherManager {
     if (OriginalVoucher) {
       SWIFT_TASK_DEBUG_LOG("[%p] Restoring original voucher %p", this,
                            *OriginalVoucher);
-      if (voucher_needs_adopt(*OriginalVoucher)) {
+      if (swift_voucher_needs_adopt(*OriginalVoucher)) {
         auto previous = voucher_adopt(*OriginalVoucher);
         swift_voucher_release(previous);
       } else {
@@ -67,7 +67,7 @@ class VoucherManager {
     assert(job->Voucher != SWIFT_DEAD_VOUCHER);
 
     voucher_t previous;
-    if (voucher_needs_adopt(job->Voucher)) {
+    if (swift_voucher_needs_adopt(job->Voucher)) {
       // If we need to adopt the voucher, do so, and grab the old one.
       SWIFT_TASK_DEBUG_LOG("[%p] Swapping jobs to %p, adopting voucher %p",
                            this, job, job->Voucher);
@@ -104,7 +104,7 @@ class VoucherManager {
     assert(OriginalVoucher);
     assert(task->Voucher == SWIFT_DEAD_VOUCHER);
 
-    if (voucher_needs_adopt(*OriginalVoucher)) {
+    if (swift_voucher_needs_adopt(*OriginalVoucher)) {
       // Adopt the execution thread's original voucher. The task's voucher is
       // the one currently adopted, and is returned by voucher_adopt.
       task->Voucher = voucher_adopt(*OriginalVoucher);