Merge remote-tracking branch 'upstream/3.4' into merge-3.4

modules/core/src/system.cpp

@@ -1737,12 +1737,31 @@ static TlsStorage &getTlsStorage()
 #ifndef _WIN32  // pthread key destructor
 static void opencv_tls_destructor(void* pData)
 {
+    if (!g_isTlsStorageInitialized)
+        return;  // nothing to release, so prefer to avoid creation of new global structures
     getTlsStorage().releaseThread(pData);
 }
 #else // _WIN32
 #ifdef CV_USE_FLS
 static void WINAPI opencv_fls_destructor(void* pData)
 {
+    // Empiric detection of ExitProcess call
+    DWORD code = STILL_ACTIVE/*259*/;
+    BOOL res = GetExitCodeProcess(GetCurrentProcess(), &code);
+    if (res && code != STILL_ACTIVE)
+    {
+        // Looks like we are in ExitProcess() call
+        // This is FLS specific only because their callback is called before DllMain.
+        // TLS doesn't have similar problem, DllMain() is called first which mark __termination properly.
+        // Note: this workaround conflicts with ExitProcess() steps order described in documentation, however it works:
+        // 3. ... called with DLL_PROCESS_DETACH
+        // 7. The termination status of the process changes from STILL_ACTIVE to the exit value of the process.
+        // (ref: https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-exitprocess)
+        cv::__termination = true;
+    }
+
+    if (!g_isTlsStorageInitialized)
+        return;  // nothing to release, so prefer to avoid creation of new global structures
     getTlsStorage().releaseThread(pData);
 }
 #endif // CV_USE_FLS