Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!mit-eddie!snorkelwacker!apple!usc!cs.utexas.edu!tut.cis.ohio-state.edu!SPERM.OCEAN.WASHINGTON.EDU!keffer
From: keffer@SPERM.OCEAN.WASHINGTON.EDU (Tom Keffer)
Newsgroups: gnu.g++.bug
Subject: re: Variable sized objects
Message-ID: <8911151720.AA05328@sperm.ocean.washington.edu>
Date: 15 Nov 89 17:20:28 GMT
References: <8911151142.AA06795@g.oswego.edu>
Sender: daemon@tut.cis.ohio-state.edu
Distribution: gnu
Organization: GNUs Not Usenet
Lines: 28

dl> Date: Wed, 15 Nov 89 06:42:25 EST
dl> From: dl@g.oswego.edu (Doug Lea)
dl> Reply-To: dl@oswego.oswego.edu


dl> You CAN'T make variable-sized objects if they are ever to be local
dl> (auto or static). There's just no way to do it, since in C++, the
cl> sizeof() any local must be knowable at compile time. You have to make
dl> the variable-sized thing live on the freestore, and have the
dl> `externally visible' class just a pointer to it (and also manually
dl> manage its allocation/deallocation). Libg++ Strings and a few other
dl> classes do it this way.  Write me if you'd like help with the details.

dl> -Doug

This is, of course, the way I am doing it (even I know THAT ! :-).
But, it seems that I can't even do it on the freestore unless I assign
to "this", a la Stroustrup, p. 165, and that ain't allowed any more
with plain vanilla g++ 1.36 (you must specify the -fthis-is-variable
flag and take the resultant performance hit).

-tk

---
 Dr. Thomas Keffer          | Internet: keffer@ocean.washington.edu
 Rogue Wave Assoc.          | BITNET:   keffer%ocean.washington.edu@UWAVM
 Seattle, WA 98145          | uucp:     uw-beaver!ocean.washington.edu!keffer
 (206) 523-5831             | Telemail: T.KEFFER/OMNET