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Date: Sun, 21 Oct 2012 02:38:17 +0200
From: Abdoulaye Walsimou GAYE <awg@...toolkit.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH 2/4] Add basic sys/cdefs.h found on most unix

On 10/21/2012 02:11 AM, Rich Felker wrote:
> On Sun, Oct 21, 2012 at 02:13:47AM +0200, Abdoulaye Walsimou GAYE wrote:
>> On 10/21/2012 01:38 AM, Rich Felker wrote:
>>> On Sun, Oct 21, 2012 at 01:38:52AM +0200, Abdoulaye Walsimou GAYE wrote:
>>>> On 10/21/2012 01:18 AM, Isaac Dunham wrote:
>>>>> On Sat, 20 Oct 2012 22:15:43 +0200
>>>>> Abdoulaye Walsimou Gaye <awg@...toolkit.org> wrote:
>>>>>
>>>>>> Signed-off-by: Abdoulaye Walsimou Gaye <awg@...toolkit.org>
>>>>>> ---
>>>>>>   include/sys/cdefs.h |   22 ++++++++++++++++++++++
>>>>>>   1 file changed, 22 insertions(+)
>>>>>>   create mode 100644 include/sys/cdefs.h
>>>>> I'm pretty sure that the last three times sys/cdefs.h was proposed,
>>>>> it was rejected.
>>>> Unfortunately many packages (wrongly?) use to rely on macros defined there,
>>> I've found it's really very few; an equivalent sys/cdefs.h does not
>>> exist on most systems. It was never intended for use by applications;
>>> it's an internal part of glibc (and perhaps also some BSDs?) used for
>>> handling backwardsness like pre-ANSI C compilers (abstracting const
>>> away as __const, or abstracting away prototypes with __P()) and
>>> optional use of GCC-specific features.
>> But applications borrowed from systems internal and ported to others
>> systems tend to use these macros (libtirpc, libbsd come in mind).
>> Major BSD systems have it (FreeBSD, NetBSD, OpenBSD, PCBSD), it not
>> a reason to have it on linux systems but it helps/simplifies packages porting
>> from these OS.
> As it stands, these libraries/apps won't work anywhere but GNU/Linux
> (by "GNU/" I mean glibc-based) or BSD. If the offending code is
> removed and replaced with what should be there, they'd be a lot more
> portable. So I would not say sys/cdefs.h aids in porting them; I'd say
> its presence gives these libs/apps a way to be lazy and
> non-portable...

I am not the writer of these applications and going to patch old applications
that are there for a while is just not an option.


>
>>> For things like 'extern "C"', there's no reason to use sys/cdefs.h;
>>> the just writing the code it expands to inline is much more
>>> clear/informative and provides better performance as a nice side
>>> effect.
>>>
>>>> sometimes indirectly via <features.h>.
>>> I don't see what you mean by this.
>> some applications use <features.h> to get macros defined in <sys/cdefs.h>
>> as on glibc, eglibc, uClibc <features.h> have a #include <sys/cdefs.h>
> Both of these usages are incorrect and could easily be fixed (both are
> implementation-internal headers).
>
> Rich

May be it is incorrect, unfortunately it there for a while and some applications
rely on it.

cheers,
AWG


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