Date: Mon, 22 Jun 2015 01:41:51 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Pedro Giffuni <pfg@freebsd.org> Cc: Bruce Evans <brde@optusnet.com.au>, Dimitry Andric <dim@freebsd.org>, David Chisnall <theraven@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r268137 - head/sys/sys Message-ID: <20150622012426.S2603@besplex.bde.org> In-Reply-To: <5586CBCE.2010608@FreeBSD.org> References: <201407020845.s628jRG5031824@svn.freebsd.org> <5BE3492F-86A0-4CE3-A27C-8DB5EB662C64@FreeBSD.org> <55842F16.5040608@FreeBSD.org> <D58BE060-870A-4D5E-AE46-D915D9CD6A0C@FreeBSD.org> <20150620023835.N2562@besplex.bde.org> <55861046.4050501@FreeBSD.org> <20150621154332.U976@besplex.bde.org> <5586CBCE.2010608@FreeBSD.org>
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On Sun, 21 Jun 2015, Pedro Giffuni wrote: > On 06/21/15 01:09, Bruce Evans wrote: >> On Sat, 20 Jun 2015, Pedro Giffuni wrote: >* ... >>> With the patch we would use: >>> >>> __Noreturn void >>> foo(void) _dead2; >>> >>> Which is still ugly but C11-ish. >> >> That asks for the same problems as defining __weak. >> >> Why not just don't use _Noreturn? It is an unimprovement on the gcc >> attribute. The attribute works at the beginning or end, while Noreturn >> only works at the end. > > As I see it, newer (C11) software is likely to use _Noreturn in their > headers We can define _Noreturn to support this (but possibly shouldn't). The newer software many be pure C11. Then it doesn't need any definition, and just doesn't compile with non-C11 compilers. If we defined _Noreturn, it would be to use it in non-C11 software, like we do in stdlib.h. This is a fragile compatibility hack so it should be avoided if possible. We can easily avoid it in our own headers by not changing anything. Just use the old declaration, with __dead2 placed at the end. Any reasonable implementation of __attribute__() must be able to support any new attribute that a new standard might add. Bruce
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