PVS-Studio warning V511 for MySQL

const char* get_last_error_message(Error_message_buf buf)
{
  int error= GetLastError();

  buf[0]= '\0';
  FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM,
  NULL, error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
  (LPTSTR)buf, sizeof(buf), NULL );

  return buf;
}

The 'buf' object is simply a pointer.
So, the sizeof(buf) expression will return value 4 or 8 (the size of the pointer in a 32-bit/64-bit system).

This suspicious code was found in MySQL project by PVS-Studio static code analyzer.
Warning message is:
V511 The sizeof() operator returns size of the pointer, and not of the array, in 'sizeof (buf)' expression. auth_win_client common.cc 489

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/