Remove error return for adapter and change get to create temp adapter

- To handle the customer usecases, don't return uinit when the adapter
  is used after the adapter library has already closed.
- Given the global adapter is gone, but get adapter is called, then a
  temp adapter struct is allocated and an ondemand atexit cleanup of
this memory is registered.

Signed-off-by: Neil R. Spruit <neil.r.spruit@intel.com>

source/adapters/level_zero/adapter.cpp

@@ -105,13 +105,11 @@ ur_adapter_handle_t_::ur_adapter_handle_t_() {
  };
 }
 
-#if defined(_WIN32)
-void globalAdapterWindowsCleanup() {
+void globalAdapterOnDemandCleanup() {
  if (GlobalAdapter) {
  delete GlobalAdapter;
  }
 }
-#endif
 
 ur_result_t adapterStateTeardown() {
  bool LeakFound = false;
@@ -201,7 +199,7 @@ ur_result_t adapterStateTeardown() {
  // Due to multiple DLLMain definitions with SYCL, register to cleanup the
  // Global Adapter after refcnt is 0
 #if defined(_WIN32)
- std::atexit(globalAdapterWindowsCleanup);
+ std::atexit(globalAdapterOnDemandCleanup);
 #endif
 
  return UR_RESULT_SUCCESS;
@@ -227,10 +225,18 @@ UR_APIEXPORT ur_result_t UR_APICALL urAdapterGet(
  if (GlobalAdapter->RefCount++ == 0) {
  adapterStateInit();
  }
- *Adapters = GlobalAdapter;
  } else {
- return UR_RESULT_ERROR_UNINITIALIZED;
+ // If the GetAdapter is called after the Library began or was torndown,
+ // then temporarily create a new Adapter handle and register a new
+ // cleanup.
+ GlobalAdapter = new ur_adapter_handle_t_();
+ std::lock_guard<std::mutex> Lock{GlobalAdapter->Mutex};
+ if (GlobalAdapter->RefCount++ == 0) {
+ adapterStateInit();
+ }
+ std::atexit(globalAdapterOnDemandCleanup);
  }
+ *Adapters = GlobalAdapter;
  }
 
  if (NumAdapters) {
@@ -256,8 +262,6 @@ UR_APIEXPORT ur_result_t UR_APICALL urAdapterRetain(ur_adapter_handle_t) {
  if (GlobalAdapter) {
  std::lock_guard<std::mutex> Lock{GlobalAdapter->Mutex};
  GlobalAdapter->RefCount++;
- } else {
- return UR_RESULT_ERROR_UNINITIALIZED;
  }
 
  return UR_RESULT_SUCCESS;