PVS-Studio warning V555 for Scilab

size_t wcslen(const wchar_t * _Str);

char *getScilabDirectory(BOOL UnixStyle)
{
  ....
  if (wcslen(dir) - wcslen(DirTmp)>0)
  {
    dir[wcslen(dir) - wcslen(DirTmp)] = L'\0';
  }
  else return NULL;
  ....
}

This suspicious code was found in Scilab project by PVS-Studio static code analyzer.
Warning message is:
V555 The expression 'wcslen(dir) - wcslen(DirTmp) > 0' will work as 'wcslen(dir) != wcslen(DirTmp)'. getscilabdirectory.c 44

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