Date: Sat, 20 Jun 2015 20:15:50 -0500 From: Pedro Giffuni <pfg@FreeBSD.org> To: Bruce Evans <brde@optusnet.com.au>, Dimitry Andric <dim@freebsd.org> Cc: 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: <55861046.4050501@FreeBSD.org> In-Reply-To: <20150620023835.N2562@besplex.bde.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>
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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 <pfg@freebsd.org> 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’s caused):
>>>>>
>>>>> __weak is a reserved keyword in Objective-C, please pick another
>>>>> name for this. This in cdefs.h makes it impossible to include any
>>>>> FreeBSD 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 language 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 >= 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.
Pedro.
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Index: sys/sys/cdefs.h
===================================================================
--- sys/sys/cdefs.h (revision 284643)
+++ sys/sys/cdefs.h (working copy)
@@ -207,6 +207,7 @@
* a feature that we cannot live without.
*/
#ifdef lint
+#define __dead
#define __dead2
#define __pure2
#define __unused
@@ -217,11 +218,13 @@
#else
#define __weak __attribute__((__weak__))
#if !__GNUC_PREREQ__(2, 5) && !defined(__INTEL_COMPILER)
+#define __dead __volatile
#define __dead2
#define __pure2
#define __unused
#endif
#if __GNUC__ == 2 && __GNUC_MINOR__ >= 5 && __GNUC_MINOR__ < 7 && !defined(__INTEL_COMPILER)
+#define __dead __attribute__((__noreturn__))
#define __dead2 __attribute__((__noreturn__))
#define __pure2 __attribute__((__const__))
#define __unused
@@ -284,7 +287,7 @@
#if defined(__cplusplus) && __cplusplus >= 201103L
#define _Noreturn [[noreturn]]
#else
-#define _Noreturn __dead2
+#define _Noreturn __dead
#endif
#if !__has_extension(c_static_assert)
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