Fix pthread to number converstion ^KT-52429

Merge-request: KT-MR-6918
Merged-by: Alexander Shabalin <Alexander.Shabalin@jetbrains.com>

kotlin-native/backend.native/tests/interop/workerSignals/workerSignals.cpp

@@ -1,6 +1,7 @@
 #include "workerSignals.h"
 
 #include <cassert>
+#include <cstring>
 #include <pthread.h>
 #include <signal.h>
 
@@ -21,7 +22,8 @@ extern "C" void setupSignalHandler(void) {
 
 extern "C" void signalThread(uint64_t thread, int value) {
     pendingValue = value;
-    auto t = reinterpret_cast<pthread_t>(thread);
+    pthread_t t = {};
+    memcpy(&t, &thread, sizeof(pthread_t));
     auto result = pthread_kill(t, SIGUSR1);
     assert(result == 0);
 }

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

@@ -249,6 +249,14 @@ void waitInNativeState(pthread_cond_t* cond,
     CallWithThreadState<ThreadState::kNative>(WaitOnCondVar, cond, mutex, timeoutNanoseconds, microsecondsPassed);
 }
 
+KULong pthreadToNumber(pthread_t thread) {
+    static_assert(sizeof(pthread_t) <= sizeof(KULong), "Casting pthread_t to ULong will lose data");
+    // That's almost std::bit_cast. The latter requires sizeof equality of types.
+    KULong result = 0;
+    memcpy(&result, &thread, sizeof(pthread_t));
+    return result;
+}
+
 class Locker {
 public:
     explicit Locker(pthread_mutex_t* lock, bool switchThreadState = true) : lock_(lock), switchThreadState_(switchThreadState) {
@@ -639,9 +647,7 @@ class State {
       if (it == workers_.end()) {
           ThrowWorkerAlreadyTerminated();
       }
-      pthread_t thread = it->second->thread();
-      static_assert(sizeof(pthread_t) <= sizeof(KULong), "Casting pthread_t to ULong will lose data");
-      return reinterpret_cast<KULong>(thread);
+      return pthreadToNumber(it->second->thread());
   }
 
   OBJ_GETTER0(getActiveWorkers) {