Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!usc!cs.utexas.edu!uunet!ncrlnk!ncratl!scotty!dspoon
From: dspoon@scotty.Atlanta.NCR.COM (Dave Witherspoon)
Newsgroups: comp.lang.c++
Subject: Re: A solution to the multiple inclusion problem
Message-ID: <1035@scotty.Atlanta.NCR.COM>
Date: 31 Oct 89 19:42:17 GMT
References: <14240@well.UUCP} <1989Oct23.191634.6345@cs.rochester.edu> <3531@cadillac.CAD.MCC.COM>
Distribution: comp
Organization: NCR Corporation, E&M Atlanta
Lines: 33

In article <3531@cadillac.CAD.MCC.COM}, vaughan@mcc.com (Paul Vaughan) writes:
} 
}    From: dspoon@ncratl2.Atlanta.NCR.COM (Dave Witherspoon)
} 
}    Say I have 2 classes, A and B.  A contains a B*, and B contains an A*.
}    Thus, we have a circular dependency!  One proposal (that I've tried):
} 
} This may not solve your exact problem, but the way to do this is
} simply
} 
}  [...solution omitted...]
} 
} 	However, this does bring up a real issue.  This sort of thing
} works, but not when you try to define inline functions inside the .h
} files.  Putting inlines in .h files requires the inclusion of other .h
} files, that would not otherwise be necessary.  Since all base class
} and component types must be defined before a class definition, a
} single inline function can force a whole tree of .h files to be
} included, (easily 10 more files) where they would not have been
} necessary otherwise.  

I didn't go into all the other problems that happen when you don't get
your dependent files included.  A containing a B* made for an easy
example, but (as you mention) additional problems show up when you need
to invoke a B method (inline or not) from an A inline method.  Also if
A contained a B (not a B*), you're bit again.  The Coggins approach I
mentioned solve 3 problems:  (1) many files open, (2) multiple opens of
the same .h file, and (3) correct order of inclusion.

-------------------------------David Witherspoon-------------------------------
D.Witherspoon@Atlanta.NCR.COM         | "Dolphins find humans amusing, but 
NCR Retail Systems Development/Atlanta|  they don't want to talk to them."
MY OPINIONS...ALL MINE!!!             |               - David Byrne