This bug was reported by Guilherme Valarini via Openmp-dev (openmp-dev@lists.llvm.org). The link is https://lists.llvm.org/pipermail/openmp-dev/2021-February/003867.html

The following is the bug description.

In both cases, the address to a local variable is passed as the host data to be copied to the target device, but since this function can be asynchronously executed, such variables can get out of scope when the actual submission is done.


```
// File: openmp/libomptarget/src/omptarget.cpp:419
if (arg_types[i] & OMP_TGT_MAPTYPE_PTR_AND_OBJ && !IsHostPtr) {
  DP("Update pointer (" DPxMOD ") -> [" DPxMOD "]\n",
      DPxPTR(PointerTgtPtrBegin), DPxPTR(TgtPtrBegin));
  uint64_t Delta = (uint64_t)HstPtrBegin - (uint64_t)HstPtrBase;
  void *TgtPtrBase = (void *)((uint64_t)TgtPtrBegin - Delta);
  int rt = Device.submitData(PointerTgtPtrBegin, &TgtPtrBase,
                              sizeof(void *), async_info_ptr);
  if (rt != OFFLOAD_SUCCESS) {
    REPORT("Copying data to device failed.\n");
    return OFFLOAD_FAIL;
  }
  // create shadow pointers for this entry
  Device.ShadowMtx.lock();
  Device.ShadowPtrMap[Pointer_HstPtrBegin] = {
      HstPtrBase, PointerTgtPtrBegin, TgtPtrBase};
  Device.ShadowMtx.unlock();
}
```

```
// File: openmp/libomptarget/src/omptarget.cpp:1141
DP("Parent lambda base " DPxMOD "\n", DPxPTR(TgtPtrBase));
uint64_t Delta = (uint64_t)HstPtrBegin - (uint64_t)HstPtrBase;
void *TgtPtrBegin = (void *)((uintptr_t)TgtPtrBase + Delta);
void *PointerTgtPtrBegin = Device.getTgtPtrBegin(
    HstPtrVal, ArgSizes[I], IsLast, false, IsHostPtr);
if (!PointerTgtPtrBegin) {
  DP("No lambda captured variable mapped (" DPxMOD ") - ignored\n",
      DPxPTR(HstPtrVal));
  continue;
}
if (PM->RTLs.RequiresFlags & OMP_REQ_UNIFIED_SHARED_MEMORY &&
    TgtPtrBegin == HstPtrBegin) {
  DP("Unified memory is active, no need to map lambda captured"
      "variable (" DPxMOD ")\n",
      DPxPTR(HstPtrVal));
  continue;
}
DP("Update lambda reference (" DPxMOD ") -> [" DPxMOD "]\n",
    DPxPTR(PointerTgtPtrBegin), DPxPTR(TgtPtrBegin));
Ret = Device.submitData(TgtPtrBegin, &PointerTgtPtrBegin,
                        sizeof(void *), AsyncInfo);
if (Ret != OFFLOAD_SUCCESS) {
  REPORT("Copying data to device failed.\n");
  return OFFLOAD_FAIL;
}
```