Why do gcc support empty struct extension for?

[tiande <tiande@xxxxxxxxx>]

In C++ context, I understand that it might be used as base class.
But I don't understand, what does it for in C context? What is the
reason we used empty struct in C.

(This is the first time I post in this mailing list and I have search
through comp.lang.c, gcc mailing list, google to make sure that this
is not a repeated post)

e.g.

struct foo{};

or just

struct bar;

Any example of the usage?

--
Regards,
  Chong, Tian Teck
  tiande@xxxxxxxxx




--
Regards,
  Chong, Tian Teck
  tiande@xxxxxxxxx