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From: "kretz at kde dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/84949] -ffast-math bugged with respect to NaNs
Date: Fri, 18 Sep 2020 07:09:10 +0000	[thread overview]
Message-ID: <bug-84949-4-ZIruesUqQ7@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-84949-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84949

--- Comment #8 from Matthias Kretz (Vir) <kretz at kde dot org> ---
I've been doing a lot of research into the numeric_limits intent/meaning
recently. I also implemented and used alternative interpretations of "has NaN"
and "is IEC559". My conclusion: std::numeric_limits means "has NaN bitpattern"
and "has IEC559 bit layout" not "has NaNs with NaN behavior" and "has IEC559
behavior". The former are still useful even if the latter don't hold. The C++
standard could be clearer on this matter though.
Thus, it seems the status quo is working as intended. It's just that we're
missing a standard interface to ask for behavior conformance.

Any progress on this issue must go via WG21.

Besides: my patch in #6 was not accepted (ABI concerns: specifically ABI
breakage from using different -f... flags), so should this PR be closed?

       reply	other threads:[~2020-09-18  7:09 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <bug-84949-4@http.gcc.gnu.org/bugzilla/>
2020-09-18  7:09 ` kretz at kde dot org [this message]
2021-09-21  6:41 ` rguenth at gcc dot gnu.org
2023-10-10 13:58 ` pinskia at gcc dot gnu.org

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