kernel: destroy untouched static rwlocks without allocation

src/kernel/pthread.cpp

@@ -2277,7 +2277,10 @@ int KYTY_SYSV_ABI PthreadRwlockDestroy(PthreadRwlock* rwlock) {
 		return KERNEL_ERROR_EINVAL;
 	}
 
-	EXIT_NOT_IMPLEMENTED(*rwlock == nullptr);
+	// SCE_PTHREAD_RWLOCK_INITIALIZER has no allocated resources until first use.
+	if (*rwlock == nullptr) {
+		return OK;
+	}
 
 	{
 		std::lock_guard lock((*rwlock)->m);

tests/KernelFileSystemTests.cpp

@@ -101,6 +101,17 @@ void WaitForMutexTest(Predicate ready) {
   }
 }
 
+void TestStaticRwlockDestroy() {
+  using namespace Libs::LibKernel;
+  PthreadRwlock rwlock = nullptr;
+  Check(PthreadRwlockDestroy(nullptr) == KERNEL_ERROR_EINVAL &&
+            PthreadRwlockDestroy(&rwlock) == OK && rwlock == nullptr,
+        "destroy an untouched static rwlock without allocating it");
+  Check(PthreadRwlockRdlock(&rwlock) == OK && PthreadRwlockUnlock(&rwlock) == OK &&
+            PthreadRwlockDestroy(&rwlock) == OK,
+        "static rwlock remains usable after destroying its untouched initializer");
+}
+
 struct MutexWaiter {
   Libs::LibKernel::PthreadMutex *mutex;
   Libs::LibKernel::KernelUseconds timeout = 0;
@@ -2723,6 +2734,7 @@ int main(int argc, char** argv) {
   }
 
   TestMutexHandoff();
+  TestStaticRwlockDestroy();
   if (argc == 2 && std::string_view(argv[1]) == "--mutex-only") {
     subsystems.Destroy();
     std::printf("KernelFileSystemTests: mutex cases passed\n");