From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/10889 Path: news.gmane.org!.POSTED!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: libstdc++ namespace pollution Date: Wed, 4 Jan 2017 18:05:25 -0500 Message-ID: <20170104230525.GA7642@brightrain.aerifal.cx> References: <20170103182908.GH1555@brightrain.aerifal.cx> <20170103213552.GI1555@brightrain.aerifal.cx> <20170103231728.GJ1555@brightrain.aerifal.cx> <20170103233321.GK1555@brightrain.aerifal.cx> <20170103235319.GL1555@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1483571147 9385 195.159.176.226 (4 Jan 2017 23:05:47 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 4 Jan 2017 23:05:47 +0000 (UTC) User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-10902-gllmg-musl=m.gmane.org@lists.openwall.com Thu Jan 05 00:05:43 2017 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 4.84_2) (envelope-from ) id 1cOuch-000106-4S for gllmg-musl@m.gmane.org; Thu, 05 Jan 2017 00:05:35 +0100 Original-Received: (qmail 1547 invoked by uid 550); 4 Jan 2017 23:05:37 -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 1526 invoked from network); 4 Jan 2017 23:05:37 -0000 Content-Disposition: inline In-Reply-To: Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:10889 Archived-At: On Wed, Jan 04, 2017 at 02:33:46PM +0000, Justin Cormack wrote: > Almost, misses REG_R8 etc but > > sed 's/#define *\(REG_[A-Z_0-9]\{1,\}\) *\([0-9]\{1,\}\)/enum { \1 = > \2 };\n#define \1 \1/' > > works for me yes OK, I'll commit the resulting patch then. Rich > On 3 January 2017 at 23:53, Rich Felker wrote: > > On Tue, Jan 03, 2017 at 06:33:21PM -0500, Rich Felker wrote: > >> On Tue, Jan 03, 2017 at 06:17:28PM -0500, Rich Felker wrote: > >> > On Tue, Jan 03, 2017 at 10:52:19PM +0000, Justin Cormack wrote: > >> > > On 3 January 2017 at 21:35, Rich Felker wrote: > >> > > > On Tue, Jan 03, 2017 at 09:16:29PM +0000, Justin Cormack wrote: > >> > > >> On 3 January 2017 at 18:29, Rich Felker wrote: > >> > > >> > On Tue, Jan 03, 2017 at 05:44:47PM +0000, Justin Cormack wrote: > >> > > >> >> I have been trying to build a C++ program recently, and came across > >> > > >> >> the issue that > >> > > >> >> > >> > > >> >> 1. libstdc++ always defines _GNU_SOURCE see > >> > > >> >> https://gcc.gnu.org/onlinedocs/libstdc++/faq.html#faq.predefined > >> > > >> >> 2. Musl defines pretty much everything once _GNU_SOURCE is defined > >> > > >> > > >> > > >> > So does glibc. :) > >> > > >> > >> > > >> This particular issue only happens with Musl, it includes more... > >> > > > > >> > > > That might be a bug/unwanted behavior on musl's side then. Could you > >> > > > help me check? I'd be happy to remove namespace-polluting cruft that's > >> > > > not actually needed to meet what applications can reasonably expect > >> > > > from _GNU_SOURCE. > >> > > > > >> > > > >> > > This minimal test case compiles with c++ on Debian but not on Alpine: > >> > > > >> > > #include > >> > > > >> > > class ArgumentParser_x64 { > >> > > enum Register { > >> > > REG_A, > >> > > REG_B, > >> > > REG_C, > >> > > REG_D, > >> > > REG_SI, > >> > > REG_DI, > >> > > REG_BP, > >> > > REG_SP, > >> > > REG_8, > >> > > REG_9, > >> > > REG_10, > >> > > REG_11, > >> > > REG_12, > >> > > REG_13, > >> > > REG_14, > >> > > REG_15, > >> > > REG_RIP, > >> > > }; > >> > > }; > >> > > > >> > > main() {} > >> > > >> > I see. It's a bit of luck that it happens to work on glibc, I think -- > >> > they define the REG_* identifiers as enum constants and then #define > >> > them to themselves in order to satisfy programs which are checking for > >> > their presence with #ifdef. So while the above code has macros > >> > clashing with the identifier names it wants to use, they end up being > >> > benign because they're defined to themselves. > >> > > >> > In general I don't do this (the enum approach) in musl because (1) I > >> > don't like enums, and (2) it breaks things that want to use the macros > >> > in preprocessor #if conditionals. However for macros like this that > >> > aren't specified by any standard and which are fundamentally namespace > >> > pollution, it seems like a better approach, so I'm not opposed to > >> > switching. We should probably do the same on all affected archs if we > >> > do. > >> > >> After a quick glance, looks like this issue only affects x86[_64]. > >> I'll see if I can prepare a simple patch with a clean idiom we can > >> repeat elsewhere if needed. > > > > Does this sed script, run on bits/signal.h, work for you? > > > > sed 's/#define *\(REG_[A-Z_]\{1,\}\) *\([0-9]\{1,\}\)/enum { \1 = \2 };\n#define \1 \1/' > > > > I like this approach better than trying to pretty-format a big enum by > > hand because it doesn't risk mistakes. If a single big enum would be > > preferred, maybe we could do a similar sed for the body of the enum, > > but I actually don't really like the GNU-style interleaved > > enum-and-#define. > > > > Rich