From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/14388 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH] Define NULL as __null in C++ mode when using GCC or Clang. Date: Wed, 10 Jul 2019 17:16:24 -0400 Message-ID: <20190710211624.GX1506@brightrain.aerifal.cx> References: <20190709193826.GR1506@brightrain.aerifal.cx> <20190710020357.GI21055@port70.net> <871ryycs9n.fsf@oldenburg2.str.redhat.com> <20190710164446.GS1506@brightrain.aerifal.cx> <20190710204812.GV1506@brightrain.aerifal.cx> <20190710211154.GL21055@port70.net> Reply-To: musl@lists.openwall.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="92977"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-14404-gllmg-musl=m.gmane.org@lists.openwall.com Wed Jul 10 23:16:40 2019 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.89) (envelope-from ) id 1hlJx9-000O5u-Lw for gllmg-musl@m.gmane.org; Wed, 10 Jul 2019 23:16:39 +0200 Original-Received: (qmail 32292 invoked by uid 550); 10 Jul 2019 21:16:37 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 32272 invoked from network); 10 Jul 2019 21:16:36 -0000 Content-Disposition: inline In-Reply-To: <20190710211154.GL21055@port70.net> Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:14388 Archived-At: On Wed, Jul 10, 2019 at 11:11:55PM +0200, Szabolcs Nagy wrote: > * Rich Felker [2019-07-10 16:48:12 -0400]: > > On Wed, Jul 10, 2019 at 01:35:35PM -0400, James Y Knight wrote: > > > My leaning would kinda be to use > > > > nullptr in recent C++ versions and retain 0L for old ones if nullptr > > > > is a valid definition in new C++ versions, but I still wonder if > > > > having use of NULL "break maximally" isn't a better behavior with > > > > respect to ending its use... > > > > > > > > > > #define NULL nullptr is standards-valid in c++11 and later, but would be an > > > unfortunate choice to make. Both in terms of breaking working code (code > > > which is making unportable assumptions, granted), but also in terms of > > > breaking ABIs on valid code: changing the type from long to > > > decltype(nullptr) changes mangling, etc. > > > > Could you clarify how it "breaks ABI"? NULL is not a type but a macro > > expanding to an expression. Does its type somehow leak into mangled > > symbol names via templates or something? If so, this is a complication > > to any proposed change of the type. > > void f(int); > void f(long); > void f(void*); > .... > f(NULL); // if NULL is 0 vs 0L then the int vs long version is called. > > so the dispatch (and called symbol) depends on the definition of NULL > > __null behaves like 0L, nullptr would dispatch to the void* version. I see. I don't see this as ABI breakage, but rather as a change in the behavior produced by non-portable code. But I wonder if it's also possible to see ABI breakage from a change. > i think modern c++ code should use nullptr in the code. > > definition of NULL should be imo kept as 0L (that's what > you would get on older unix systems or on openbsd anyway) > apparently some ppl prefer __null. Do you know if OpenBSD has a reason they do it this way? Rich