fixup! fixup! [K/N][New MM] Disallow getting thread data for detached threads

kotlin-native/runtime/src/legacymm/cpp/Memory.cpp

@@ -3739,7 +3739,6 @@ ALWAYS_INLINE void kotlin::AssertThreadState(MemoryState* thread, std::initializ
 }
 
 MemoryState* kotlin::mm::GetMemoryState() noexcept {
-    RuntimeAssert(memoryState != nullptr, "Thread is not attached to the runtime");
     return ::memoryState;
 }
 

kotlin-native/runtime/src/main/cpp/Memory.h

@@ -389,7 +389,8 @@ namespace kotlin {
 namespace mm {
 
 // Returns the MemoryState for the current thread.
-// The current thread must be attached to the runtime.
+// For the new MM, the current thread must be attached to the runtime.
+// For the legacy MM, returns nullptr if called on a thread that is not attached to the runtime.
 // Try not to use it very often, as (1) thread local access can be slow on some platforms,
 // (2) TLS gets deallocated before our thread destruction hooks run.
 MemoryState* GetMemoryState() noexcept;

kotlin-native/runtime/src/main/cpp/MemoryTest.cpp

@@ -12,7 +12,11 @@
 using namespace kotlin;
 
 TEST(MemoryStateTestDeathTest, GetMemoryStateForUnregisteredThread) {
-    EXPECT_DEATH(mm::GetMemoryState(), "Thread is not attached to the runtime");
+    if (CurrentMemoryModel == MemoryModel::kExperimental) {
+        EXPECT_DEATH(mm::GetMemoryState(), "Thread is not attached to the runtime");
+    } else {
+        EXPECT_EQ(mm::GetMemoryState(), nullptr);
+    }
 }
 
 TEST(MemoryStateTest, GetMemoryStateForRegisteredThread) {