From 3854316073351404394 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,7538bd92d6a9557a X-Google-Attributes: gidf78e5,public X-Google-ArrivalTime: 1995-01-21 08:00:30 PST Path: nntp.gmd.de!newsserver.jvnc.net!nntpserver.pppl.gov!princeton!gw1.att.com!fnnews.fnal.gov!uwm.edu!vixen.cso.uiuc.edu!howland.reston.ans.net!pipex!sunic!news.lth.se!nic.lth.se!dag From: dag@control.lth.se (Dag Bruck) Newsgroups: comp.std.c++ Subject: Re: short enum, bool Date: 21 Jan 1995 16:00:30 GMT Organization: Department of Automatic Control, Lund, Sweden Lines: 39 Message-ID: References: <790640242snz@thone.demon.co.uk> NNTP-Posting-Host: control.lth.se In-reply-to: andys@thone.demon.co.uk's message of Fri, 20 Jan 1995 22:17:22 +0000 >>>>> "A" == Andy Sawyer writes: A> In article A> baynes@ukpsshp1.serigate.philips.nl "Stephen Baynes" writes: A> [snip stuff about 'short enums'] >> Some C and C++ compilers do offer this as an extension. However for >> space saving it is unecessary - just buy yourself a good compiler - >> this will chose the size of an enum according to the range of the >> enumeration values you specified for it. A> Since the compiler is, as you A> say, free to choose the size of an enum, what happens in the A> following case: The compiler is somewhat constrained by the rules of the C++ working paper, so we can say a few things about your examples. A> enum little { l_lo = 0, l_hi = 1 }; // Will fit in a single bit An enum which is not a bitfield must be an addressable unit, so sizeof(any enum type) >= 1. A> enum big { b_lo = 0, b_hi = 256 }; // Needs at least 9 bits so sizeof(big) >= 2. A> enum big_x { big_x_lo = 1, big_x_hi = 256 }; A> A> Would it be legal for a compiler to implement this as an 8 bit A> value, applying a +/- 1 adjustment on conversions to/from the type? A> What about a single bit? (Probably not the latter - but the A> former?) No neither is legal, so sizeof(big_x) >= 2. -- Dag Bruck