size of empty classes

Article View: gnu.g++.bug

Article #343

#343

From: Root Boy Jim
Date: Mon, 14 Aug 1989 16:13

22 lines
1402 bytes

? From: chatty%FRLRI61.BITNET@cunyvm.cuny.edu

? I just discovered that an empty class has a non-null size. Is that
? intentional?  If it is, what are those 2 bytes for?  Until now, I
? thought having an empty base class was for free. I am disappointed.

? I use g++ 1.35.1- on a Sun3 running OS 3.5.

Just a bit of speculation here. I hope you don't think all that
whiz-bang object-oriented stuff comes for free. Most likely those two
bytes are a pointer into some table telling you what class the thing
really is. Remember that when deriving one class from another, some
means of dynamically determining to which class an object belongs
must be provided. The higher level the language, the farther you
get from what the thing really is. Live with it.

?    Stephane Chatty      chatty@frlri61.bitnet, chatty@lri.lri.fr
? LRI, Universite d'Orsay
?    Orsay, FRANCE

	Root Boy Jim
	Have GNU, Will Travel.

Technical Details

Message-ID: <8908141613.AA23693@dsys.ncsl.nist.gov>

Path:

arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!bionet!bloom-beacon!tut.cis.ohio-state.edu!DSYS.NCSL.NIST.GOV!rbj

Show Full Headers

Complete Article Headers

Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!bionet!bloom-beacon!tut.cis.ohio-state.edu!DSYS.NCSL.NIST.GOV!rbj
From: rbj@DSYS.NCSL.NIST.GOV (Root Boy Jim)
Newsgroups: gnu.g++.bug
Subject: size of empty classes
Message-ID: <8908141613.AA23693@dsys.ncsl.nist.gov>
Date: 14 Aug 89 16:13:26 GMT
Sender: daemon@tut.cis.ohio-state.edu
Distribution: gnu
Organization: National Institute of Standards and Technology
 formerly National Bureau of Standards
Lines: 22