svn commit: r268137 - head/sys/sys

[Pedro Giffuni]

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 at 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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