From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/6663 Path: news.gmane.org!not-for-mail From: Jens Gustedt Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH 1/4] the CMPLX macros must be usable in initializations of static variables Date: Wed, 03 Dec 2014 10:18:31 +0100 Message-ID: <1417598311.4936.1220.camel@eris.loria.fr> References: <1417007215.28402.107.camel@eris.loria.fr> <20141202174940.GB29621@brightrain.aerifal.cx> <1417547432.4936.1103.camel@eris.loria.fr> <20141202194210.GF29621@brightrain.aerifal.cx> <1417557612.4936.1138.camel@eris.loria.fr> <20141202224754.GK29621@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-fAB2JOCaxX5eiMxAzLJO" X-Trace: ger.gmane.org 1417598335 16126 80.91.229.3 (3 Dec 2014 09:18:55 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 3 Dec 2014 09:18:55 +0000 (UTC) To: musl Original-X-From: musl-return-6676-gllmg-musl=m.gmane.org@lists.openwall.com Wed Dec 03 10:18:48 2014 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by plane.gmane.org with smtp (Exim 4.69) (envelope-from ) id 1Xw659-0003PB-FV for gllmg-musl@m.gmane.org; Wed, 03 Dec 2014 10:18:47 +0100 Original-Received: (qmail 25817 invoked by uid 550); 3 Dec 2014 09:18:43 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: Original-Received: (qmail 25807 invoked from network); 3 Dec 2014 09:18:43 -0000 X-IronPort-AV: E=Sophos;i="5.07,506,1413237600"; d="scan'";a="110850116" In-Reply-To: <20141202224754.GK29621@brightrain.aerifal.cx> Face: 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Cj15cu23XZI4/826Px/xqB37z547sPH374oOvnKTsOb+1zuCoImZARM8ZiLlKkXcWOcoFRJ+Do/CwFO4e2DEe+9Ti+ZXA8ny/cU+X4bMKRZxZIVEiqXI6/+NKuUzPHb7z40ovnX3zx+Ctuq38HyuqWG7Tu+A0AAAAASUVORK5CYII= X-Mailer: Evolution 3.4.4-3 Xref: news.gmane.org gmane.linux.lib.musl.general:6663 Archived-At: --=-fAB2JOCaxX5eiMxAzLJO Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hello, Am Dienstag, den 02.12.2014, 17:47 -0500 schrieb Rich Felker: > On Tue, Dec 02, 2014 at 11:00:12PM +0100, Jens Gustedt wrote: > Then what about something like >=20 > #if __clang__ // && __clang_major__*100+__clang_minor__ <=3D xxxxx > // use clang compound literal hack > #elif __GNUC__*100+__GNUC_MINOR__ >=3D 407 > // use __builtin_complex > #else > // use _Complex_I with mult and add > #endif >=20 > or alternatively: >=20 > #if __clang__ // && __clang_major__*100+__clang_minor__ <=3D xxxxx > // use clang compound literal hack > #else > // use __builtin_complex > #endif >=20 > I somewhat prefer the latter since the _Complex_I form is never really > correct (INF/NAN issues) and it gives better fallback behavior > assuming other compilers will implement __builtin_complex but might > not identify themselves as "GNU C >=3D 4.7". It also produces an error > on compilers that can't give the right behavior for INF/NAN rather > than silently miscompiling the code. I agree with your analysis, we should avoid using _Complex_I, here. For the implementation I don't agree completely. Version number games are not the right thing for clang, they don't support this, in a sense in the same way that you don't want a macro that identifies musl. They have their feature/builtin test framework, we should use that. This then would kick in whenever they decide to implement that builtin. But still, I'd like to have a version with _Imaginary_I, see below. > > > > > _Imaginary_I > > > > > is not supported yet at all and would require further changes to = this > > > > > header to add anyway (this header is responsible for defining it)= , so > > > > > conditioning on its definition is not meaningful. > > > >=20 > > > > I am not sure of that. It could also come directly from the compile= r > > > > just as it defines some __SOMETHING__ macros before any include > > >=20 > > > I don't think so. Consider: > > >=20 > > > #undef _Imaginary_I > > > #include > > >=20 > > > Perhaps this is non-conforming for technical reasons, > >=20 > > it is non-conforming >=20 > Because of the _-prefixed namespace? Yes, an implementation simply *mustn't* touch any identifier that starts with underscore and capital letter. Period. > Per my understanding, it's > conforming to #undef macros provided by the standard headers in many > cases. > Eliminating a function-like macro to get at the underlying > function is one such usage mentioned in the standard, but I think > there are others too. I don't know of many, and these are explicitly named. And all of this is *not* the same thing as the case above. This concerns e.g "complex" and "I" which are otherwise not reserved, and not e.g "_Complex_I" that falls under the same rule as _Imaginary_I. > > But if you want to avoid that branch, I understand. _Imaginary_I would > > be *the* way to solve all of this easily, sigh. >=20 > Yes, I really wish GCC would support it, especially since Annex G > _requires_ _Imaginary_I, and glibc falsely advertises Annex G support > via the __STDC_IEC_559_COMPLEX__ macro despite not having > _Imaginary_I. But the glibc folks seem to think this is a non-issue > and I haven't seen any interest in fixing it on the GCC side. argh, I wasn't aware of that, what a mess. yes _Imaginary and all that comes with it is really an important feature of that Annex, e.g functions returning _Imaginary values when known to have such values. So I keep my claim for a first case version with _Imaginary_I up :) we should encourage compiler implementors to provide this feature. I looked a bit around and I found that - Keil supports imaginary - for Cray compilers 1.0i is pure imaginary and not complex, but they don't explain exactly what happens if you use this in arithmetic Jens --=20 :: INRIA Nancy Grand Est ::: AlGorille ::: ICube/ICPS ::: :: ::::::::::::::: office Strasbourg : +33 368854536 :: :: :::::::::::::::::::::: gsm France : +33 651400183 :: :: ::::::::::::::: gsm international : +49 15737185122 :: :: http://icube-icps.unistra.fr/index.php/Jens_Gustedt :: --=-fAB2JOCaxX5eiMxAzLJO Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEABECAAYFAlR+1WcACgkQD9PoadrVN+K4qQCfZG3001CElYbZJIt0XVCO4z1r LhgAnjQrr2FbClZ1OJ7t1oC/x1J8fIpS =K2+v -----END PGP SIGNATURE----- --=-fAB2JOCaxX5eiMxAzLJO--