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From: Alejandro Colomar <colomar.6.4.3@gmail.com>
To: Joseph Myers <joseph@codesourcery.com>
Cc: Jonathan Wakely <jwakely.gcc@gmail.com>,
	"gcc@gcc.gnu.org" <gcc@gcc.gnu.org>,
	linux-man <linux-man@vger.kernel.org>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Subject: Re: [RFC] man7/system_data_types.7: Document [unsigned] __int128
Date: Fri, 2 Oct 2020 10:10:04 +0200	[thread overview]
Message-ID: <5e12ffdb-4b7b-0720-98a1-3c111acff6ae@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.21.2010011724580.4323@digraph.polyomino.org.uk>

On 2020-10-01 15:46, Jonathan Wakely wrote:
 > I hope WG14 will adopt something like
 > http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2465.pdf  and the
 > whole mess will go away.
 >
 > intmax_t will be deprecated, and implementations can provide 128-bit
 > integers without caveats.


On 2020-10-01 19:31, Joseph Myers wrote:
> On Thu, 1 Oct 2020, Alejandro Colomar via Gcc wrote:
> 
>> Because 'intmax_t' has a bug
>> (actually I know GCC rejected the bug report,
>> but the problem is still there and users should be informed about this)
>> which is related to __int128.
> 
> __int128 is not an integer type as defined by any existing version of ISO
> C, precisely because it's wider than intmax_t, and changing intmax_t would
> be a big ABI problem (involving new symbol versions for about 100
> printf/scanf-related functions in glibc, 200 on platforms with multiple
> long double variants).
> 
> See the proposed removal of intmax_t in C2x (accepted in principle at the
> first virtual Freiburg meeting, but so far without any wording accepted
> for any specific approach to removal regarding e.g. preprocessor
> arithmetic and other places depending on intmax_t).  That removal would
> allow __int128 to be considered an extended integer type as defined by C2x
> and later (with int128_t typedef in <stdint.h>, etc.), if desired.
> 


Thanks for pointing out that the standard acknowledges
the bug in [u]intmax_t.  It's good to know.
Also good to know they plan to fix it.

Thanks,

Alex

      reply	other threads:[~2020-10-02  8:10 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-01  9:24 [RFC] man7/system_data_types.7: Document [unsigned] __int128 Alejandro Colomar
2020-10-01  9:57 ` Jonathan Wakely
2020-10-01 10:14   ` Alejandro Colomar
2020-10-01 10:50     ` Jonathan Wakely
2020-10-01 11:24       ` Alejandro Colomar
2020-10-01 11:46         ` Jonathan Wakely
2020-10-01 12:54     ` Szabolcs Nagy
2020-10-01 13:22       ` Alejandro Colomar
2020-10-01 13:46         ` Jonathan Wakely
2020-10-01 17:31     ` Joseph Myers
2020-10-02  8:10       ` Alejandro Colomar [this message]

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