From owner-svn-src-head@FreeBSD.ORG Sun Jun 21 11:49:29 2015 Return-Path: Delivered-To: svn-src-head@hub.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 9C8E88D9 for ; Sun, 21 Jun 2015 11:49:29 +0000 (UTC) (envelope-from oliver.pinter@hardenedbsd.org) Received: from mail-wi0-f180.google.com (mail-wi0-f180.google.com [209.85.212.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 5B0E0210 for ; Sun, 21 Jun 2015 11:49:29 +0000 (UTC) (envelope-from oliver.pinter@hardenedbsd.org) Received: by wicnd19 with SMTP id nd19so53548693wic.1 for ; Sun, 21 Jun 2015 04:49:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=1kRxc5pcT/9cf0rz0u//HUxCt6mNirQ+sBShaVYOQyQ=; b=cFmr6aLluoN7RK8J+Ch67pbzoQ9zQRDRUyA+RtYo+13U5mQ/BGqjroCxaWoP0tzXTu ryYKKKu2MP6IF8rFf0Kgo/KbpR8bZHtbkvqetw1TmyjElEsXpMQPqK/CO/ZinH2N1JKD 8kdQ902xcphqjMeWoQjdAofm4ot3dFTz3gL0Leg9CJ1E/s8PlQdhJB+CfuRHbkbAr+wF Su7eI6ptGr0WCi7xFIRjv2r3ReEm+3uc5s+dryWFF2OUw6nFqmXiWKHPaPTV7EWMjqJh WTKz+cdXN/G3+K0kRcXNlAAQO8H/ss8rJd4jBJwcKJN1L/NA6KHm0kvqhr3laoCnA/jT QjCA== X-Gm-Message-State: ALoCoQnIWhYcQhMsS8ikJ0PNTlulmDIpH7GofByRK26UHbIHGca5S9EMfZKN0WcivuVXWSTdorSp MIME-Version: 1.0 X-Received: by 10.194.187.51 with SMTP id fp19mr28596437wjc.67.1434887367385; Sun, 21 Jun 2015 04:49:27 -0700 (PDT) Received: by 10.194.81.106 with HTTP; Sun, 21 Jun 2015 04:49:27 -0700 (PDT) In-Reply-To: <20150621154332.U976@besplex.bde.org> References: <201407020845.s628jRG5031824@svn.freebsd.org> <5BE3492F-86A0-4CE3-A27C-8DB5EB662C64@FreeBSD.org> <55842F16.5040608@FreeBSD.org> <20150620023835.N2562@besplex.bde.org> <55861046.4050501@FreeBSD.org> <20150621154332.U976@besplex.bde.org> Date: Sun, 21 Jun 2015 13:49:27 +0200 Message-ID: Subject: Re: svn commit: r268137 - head/sys/sys From: Oliver Pinter To: Bruce Evans Cc: Pedro Giffuni , src-committers@freebsd.org, Dimitry Andric , svn-src-all@freebsd.org, David Chisnall , svn-src-head@freebsd.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 21 Jun 2015 11:49:29 -0000 On 6/21/15, Bruce Evans wrote: > On Sat, 20 Jun 2015, Pedro Giffuni wrote: > >> On 06/19/15 12:23, Bruce Evans wrote: >>> On Fri, 19 Jun 2015, Dimitry Andric wrote: >>> >>>> On 19 Jun 2015, at 17:02, Pedro Giffuni wrote: >>>>> >>>>>> On 19/06/2015 05:16 a.m., David Chisnall wrote: >>>>>>> I only just caught this (having seen the fallout from NetBSD doing >>>>>>> the >>>>>>> same thing in a shipping release and the pain that it=E2=80=99s cau= sed): >>>>>>> __weak is a reserved keyword in Objective-C, please pick another na= me >>>>>>> >>>>>>> for this. This in cdefs.h makes it impossible to include any FreeB= SD >>>>>>> >>>>>>> standard headers in Objective-C programs (of which we have a couple >>>>>>> of >>>>>>> hundred in ports) if they use any of the modern Objective-C languag= e >>>>>>> >>>>>>> modes. >>>> ... >>>>> Closely related to this, we are redefining _Noreturn, which is a >>>>> reserved >>>>> keyword in C11. >>>> >>>> No, sys/cdefs.h has: >>>> >>>> 254 /* >>>> 255 * Keywords added in C11. >>>> 256 */ >>>> 257 >>>> 258 #if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 201112L || >>>> defined(lint) >>>> [...] >>>> 284 #if defined(__cplusplus) && __cplusplus >=3D 201103L >>>> 285 #define _Noreturn [[noreturn]] >>>> 286 #else >>>> 287 #define _Noreturn __dead2 >>>> 288 #endif >>>> [...] >>>> 320 #endif /* __STDC_VERSION__ || __STDC_VERSION__ < 201112L */ >>>> >>>> So the whole block redefining all the _Xxx identifiers is skipped for >>>> C11 and higher. >>> >>> I probably pointed this out incorrectly to Pedro. >>> >>> All uses of _Noreturn are still broken, and also ugly. __dead2 is the >>> gcc-2 compatible version of the gcc-1 compatible macro __dead. It is >>> syntactically different from __dead and _Noreturn. It must be placed >>> after the function parameter list instead of in the function type >>> declarator because old versions of gcc only accept attributes there. >>> __dead and presumably _Noreturn must be placed in the function type >>> declarator. This is incompatible, and also uglier. >>> >> I was thinking that _Noreturn can be fixed for older compilers >> less disruptively. >> >> I haven't tested the attached patch the idea is to resurrect >> __dead and use it for _Noreturn. >> >>> Correct version with ugly declarations: >>> >>> __dead void >>> foo(void) __dead2; >>> >> >> 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. I checked this: > > pts/23:bde@freefall:~/s> cc -O -S a.c -std=3Dc11 > a.c:3:26: error: '_Noreturn' keyword must precede function declarator > _Noreturn void bar(void) _Noreturn; > ^ > > I also checked if __dead2 works at the beginning in gcc-2.95.4. It > does, but other headers are broken, so the support for gcc-2.95.4 in > sys/cdefs.h is almost useless: > > pts/23:bde@freefall:~/s> gcc295 -O -S a.c > In file included from /usr/include/machine/_types.h:6, > from /usr/include/sys/_types.h:33, > from /usr/include/x86/endian.h:37, > from /usr/include/machine/endian.h:6, > from /usr/include/sys/types.h:44, > from a.c:1: > /usr/include/x86/_types.h:161: syntax error before `__gnuc_va_list' > /usr/include/x86/_types.h:161: warning: data definition has no type or > storage c > lass > > Here is the broken part of x86/_types.h: > > %%% > #ifdef __GNUCLIKE_BUILTIN_VARARGS > typedef __builtin_va_list __va_list; /* internally known to gcc */ > #elif defined(lint) > typedef char * __va_list; /* pretend */ > #endif > #if defined(__GNUC_VA_LIST_COMPATIBILITY) && !defined(__GNUC_VA_LIST) \ > && !defined(__NO_GNUC_VA_LIST) > #define __GNUC_VA_LIST > meta: next is line 161: > typedef __va_list __gnuc_va_list; /* compatibility w/GNU headers*/ > #endif > %%% > > Despite (rather, because of) mounds of ifdefs to support old gcc, it > doesn't > actually work. > > is honestly broken. It knows that it depends on the gcc featu= re > __GNUCLIKE_BUILTIN_STDARG, and aborts with an #error when it is not > available. > All of the _GNUCLIKE_BUILTIN_* macros for variadic args are controlled by > sys/cdefs.h. They are defined when the compiler is either gcc newer than > gcc-2.95 or is icc. Btw, is there anyone, who tries to compile the _recent_ head or 10-STABLE with gcc-4.x>=3D ? > > Bruce