Re: git: 67d1a1cd9e77 - main - cdefs.h: Remove support for pre gcc 4.0

On 7/2/24 12:30, Warner Losh wrote:
> Hey John,
> 
> On Tue, Jul 2, 2024 at 9:44 AM John Baldwin <jhb@freebsd.org> wrote:
> 
>> On 7/1/24 4:09 PM, Warner Losh wrote:
>>> On Mon, Jul 1, 2024, 3:53 PM John Baldwin <jhb@freebsd.org> wrote:
>>>
>>>> On 6/20/24 7:41 PM, Warner Losh wrote:
>>>>> The branch main has been updated by imp:
>>>>>
>>>>> URL:
>>>>
>> https://cgit.FreeBSD.org/src/commit/?id=67d1a1cd9e772e2ef94003579f4fbc271d38be7d
>>>>>
>>>>> commit 67d1a1cd9e772e2ef94003579f4fbc271d38be7d
>>>>> Author:     Warner Losh <imp@FreeBSD.org>
>>>>> AuthorDate: 2024-06-20 23:02:56 +0000
>>>>> Commit:     Warner Losh <imp@FreeBSD.org>
>>>>> CommitDate: 2024-06-21 02:41:08 +0000
>>>>>
>>>>>        cdefs.h: Remove support for pre gcc 4.0
>>>>>
>>>>>        All supported compilers support the gcc 3 attribute extensions.
>>>> Remove
>>>>>        the #else clauses for this. Also, latter-day pcc compilers also
>>>> define
>>>>>        __GNUC__, so there's not need to also test for __PCC__.
>>>>>
>>>>>        Reviewed by:            brooks
>>>>>        Differential Revision:  https://reviews.freebsd.org/D45654
>>>>>        Sponsored by:           Netflix
>>>>> ---
>>>>>     sys/sys/cdefs.h | 42 ++++--------------------------------------
>>>>>     1 file changed, 4 insertions(+), 38 deletions(-)
>>>>>
>>>>> diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
>>>>> index 88019819eb35..a6ecdca5d8b9 100644
>>>>> --- a/sys/sys/cdefs.h
>>>>> +++ b/sys/sys/cdefs.h
>>>>> @@ -408,15 +389,10 @@
>>>>>      * assign pointer x to a local variable, to check that its type is
>>>>>      * compatible with member m.
>>>>>      */
>>>>> -#if __GNUC_PREREQ__(3, 1)
>>>>>     #define     __containerof(x, s, m) ({
>>>>        \
>>>>>         const volatile __typeof(((s *)0)->m) *__x = (x);
>> \
>>>>>         __DEQUALIFY(s *, (const volatile char *)__x - __offsetof(s,
>> m));\
>>>>>     })
>>>>> -#else
>>>>> -#define      __containerof(x, s, m)
>>>>         \
>>>>> -     __DEQUALIFY(s *, (const volatile char *)(x) - __offsetof(s, m))
>>>>> -#endif
>>>>>
>>>>>     /*
>>>>>      * Compiler-dependent macros to declare that functions take
>> printf-like
>>>>> @@ -434,14 +410,8 @@
>>>>>     #define     __strftimelike(fmtarg, firstvararg) \
>>>>>             __attribute__((__format__ (__strftime__, fmtarg,
>> firstvararg)))
>>>>>
>>>>> -/* Compiler-dependent macros that rely on FreeBSD-specific extensions.
>>>> */
>>>>> -#if defined(__FreeBSD_cc_version) && __FreeBSD_cc_version >= 300001
>> && \
>>>>> -    defined(__GNUC__)
>>>>>     #define     __printf0like(fmtarg, firstvararg) \
>>>>>             __attribute__((__format__ (__printf0__, fmtarg,
>> firstvararg)))
>>>>> -#else
>>>>> -#define      __printf0like(fmtarg, firstvararg)
>>>>> -#endif
>>>>
>>>> Does this still work with external GCC?  I didn't think printf0 was
>>>> supported
>>>> by external GCC (or maybe I had to readd it in the port and that's what
>> I
>>>> remember).  Ah, yes, printf0 is a local patch in the devel/freebsd-gccX
>>>> ports, but is not available in stock GCC (e.g. lang/gcc does not support
>>>> it).
>>>>
>>>
>>> Ah. That would explain why it just worked for me. That's what I tested
>>> with. Clang also seemed happy with it. But that was the in tree clang. Is
>>> there a similar issue? Gnuc is defined for both.
>>
>> So we don't support building the base system with lang/gcc, only
>> devel/freebsd-gccX (which has a local patch to add printf0 support).
>> The only question might be, do we support using __printf0like for things
>> that aren't in the base system that could be built with lang/gcc.  If so,
>> we might need to guard this somehow.  I'm not sure though that we care
>> about random software not in base using a FreeBSD-specific keyword from
>> <sys/cdefs.h>.
>>
> 
> Yes. The question is "do we use __printf0like  in our headers" since we
> definitely
> can't build FreeBSD itself w/o at least some of the extensions for other
> things...
> and the answer is "yes". err.h uses it, for example, as does setproctitle
> in stdlib.h
> 
> The interesting thing for me is that gcc13 will produce no warnings if I
> include errr.h
> because -Wsystem-header is off. With it on, warnings crop up too. This is
> why my testing
> didn't see it...
> 
> It looks like clang has it as a builtin for all versions we care about, so
> I'll create a phab to add some
> of this back. Maybe we should upstream what we have, for this and
> freebsd_printf since that's also
> in clang and one of the small number of patches we have for the lang/gcc*
> family?

Yeah, I should do my FSF paperwork for GCC sometime and try to upstream at
least the printf changes and a few others (i386 defaulting to i686 on
recent releases as well)

-- 
John Baldwin