PVS-Studio warning V594 for ReactOS

FF_T_WCHAR FileName[FF_MAX_FILENAME];

FF_T_UINT32 FF_FindEntryInDir(....) {
  ....
  FF_T_WCHAR *lastPtr = pDirent->FileName +
                        sizeof(pDirent->FileName);
  ....
  lastPtr[-1] = '\0';
  ....
}

This is what should have been written here: FF_T_WCHAR *lastPtr = pDirent->FileName + sizeof(pDirent->FileName) / sizeof(pDirent->FileName[0]);

This suspicious code was found in ReactOS project by PVS-Studio static code analyzer.
Warning message is:
V594 The pointer steps out of array's bounds. ff_dir.c 260

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/