From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: grischka Newsgroups: gmane.emacs.devel Subject: Re: enum may be signed Date: Sat, 01 May 2010 20:51:11 +0200 Message-ID: <4BDC781F.5050609@gmx.de> References: <4BDC4D04.1040102@gmx.de> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: dough.gmane.org 1272739897 522 80.91.229.12 (1 May 2010 18:51:37 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Sat, 1 May 2010 18:51:37 +0000 (UTC) Cc: emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sat May 01 20:51:35 2010 connect(): No such file or directory Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1O8Hmo-0002l3-Ms for ged-emacs-devel@m.gmane.org; Sat, 01 May 2010 20:51:34 +0200 Original-Received: from localhost ([127.0.0.1]:60039 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O8Hmo-0004Oc-2k for ged-emacs-devel@m.gmane.org; Sat, 01 May 2010 14:51:34 -0400 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1O8Hmi-0004ON-6V for emacs-devel@gnu.org; Sat, 01 May 2010 14:51:28 -0400 Original-Received: from [140.186.70.92] (port=59523 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O8Hmg-0004OA-4F for emacs-devel@gnu.org; Sat, 01 May 2010 14:51:26 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1O8Hmf-0000DJ-5H for emacs-devel@gnu.org; Sat, 01 May 2010 14:51:25 -0400 Original-Received: from mail.gmx.net ([213.165.64.20]:40439) by eggs.gnu.org with smtp (Exim 4.69) (envelope-from ) id 1O8Hme-0000DB-Np for emacs-devel@gnu.org; Sat, 01 May 2010 14:51:25 -0400 Original-Received: (qmail invoked by alias); 01 May 2010 18:51:22 -0000 Original-Received: from 184.121.113.82.net.de.o2.com (EHLO [10.54.31.65]) [82.113.121.184] by mail.gmx.net (mp053) with SMTP; 01 May 2010 20:51:22 +0200 X-Authenticated: #18588216 X-Provags-ID: V01U2FsdGVkX1+lmoA/kfWl3pKYqkT66Wl6k94auZeE7+x9mRSaY+ 1cH+sLFAzafSTE User-Agent: Thunderbird 2.0.0.23 (Windows/20090812) In-Reply-To: X-Y-GMX-Trusted: 0 X-FuHaFi: 0.58999999999999997 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:124397 Archived-At: Stefan Monnier wrote: >> + enum symbol_redirect redirect : 3; > >> Note that this breaks with compilers where enums can be signed (e.g. MSVC), >> Because value 4 doesn't fit into 3 bits (signed), it is read as -4 and >> breaks related switch statements (e.g. data.c:set_internal) > > Interesting. I didn't know about that part of the C language. Is it > possible to specify that this is an unsigned enum somehow? > I've tried "enum symbol_redirect redirect : 3;" but at least GCC didn't > like it. Planned for C++0x: http://en.wikipedia.org/wiki/C%2B%2B0x#Strongly_typed_enumerations > Of course we can add one more bit (we have plenty of bits left there), > but I'd first like to know how this is usually handled, since it seems > to imply that MSVC always requires one extra bit to store enums. Good old "unsigned redirect : 3;" works as expected. Btw, check also "enum Lisp_Type type : GCTYPEBITS;". --- grischka > > > Stefan >