Re: Compiler performance

[dewar@cs.nyu.edu (Robert Dewar)]

T.E.D. said

"Hmmm. What would the "copyleft" symbol look like? Perhaps a backwards
"C" in a circle?"

Probably there was a smiley missing there, but just in case anyone is
confused, there is no such thing as copyleft. It is simply a (commonly
used) informal term to describe copyrighted documents distributed under
the General Public License (GPL). All GPL'ed documents contain a formal
copyright statement, along with a notice that the GPL applies to the
document.

For example, here is the header on GNAT compiler files:

--        Copyright (C) 1992,1993,1994 Free Software Foundation, Inc.       --
--                                                                          --
-- GNAT is free software;  you can  redistribute it  and/or modify it under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 2,  or (at your option) any later ver- --
-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
-- for  more details.  You should have  received  a copy of the GNU General --
-- Public License  distributed with GNAT;  see file COPYING.  If not, write --
-- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
-- MA 02111-1307, USA.                                                      --
--                                                                          --
-- GNAT was originally developed  by the GNAT team at  New York University. --
-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --

In the case of runtime library files, an additional paragraph is added:

--                                                                          --
-- As a special exception,  if other files  instantiate  generics from this --
-- unit, or you link  this unit with other files  to produce an executable, --
-- this  unit  does not  by itself cause  the resulting  executable  to  be --
-- covered  by the  GNU  General  Public  License.  This exception does not --
-- however invalidate  any other reasons why  the executable file  might be --
-- covered by the  GNU Public License.                                      --

This additional paragraph ensures that you can freely include GNAT runtime
code in your application without your application becoming subject itself
to GPL distribution rules. This is what makes it possible to have
proprietary or otherwise protected code written using GNAT.