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LibJS: Use __builtin_isnan in static_assert instead of isnan

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For the fuzzer build isnan was not usable in a constexpr context however
__builtin_isnan seems to always be.

Also while we're here add my name to the copyright since I forgot after
the Value rewrite.
This commit is contained in:
davidot 2022-08-23 20:24:59 +02:00 committed by Linus Groh
parent 34a09bbb54
commit a9d2d806b6
Notes: sideshowbarker 2024-07-17 07:49:58 +09:00 
Author: https://github.com/davidot
Commit: https://github.com/SerenityOS/serenity/commit/a9d2d806b6
Pull-request: https://github.com/SerenityOS/serenity/pull/14992
Reviewed-by: https://github.com/BertalanD ✅
2 changed files with 5 additions and 2 deletions
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1
Userland/Libraries/LibJS/Runtime/Value.cpp
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@ -1,6 +1,7 @@
/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020-2022, Linus Groh <linusg@serenityos.org>
* Copyright (c) 2022, David Tuin <davidot@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/

6
Userland/Libraries/LibJS/Runtime/Value.h
View file

@ -1,6 +1,7 @@
/*
* Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2020-2022, Linus Groh <linusg@serenityos.org>
* Copyright (c) 2022, David Tuin <davidot@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -47,8 +48,9 @@ static_assert(POSITIVE_INFINITY_BITS == 0x7FF0000000000000);
static_assert(NEGATIVE_INFINITY_BITS == 0xFFF0000000000000);
// However as long as any bit is set in the mantissa with the exponent of all
// ones this value is a NaN, and it even ignores the sign bit.
static_assert(isnan(bit_cast<double>(0x7FF0000000000001)));
static_assert(isnan(bit_cast<double>(0xFFF0000000040000)));
// (NOTE: we have to use __builtin_isnan here since some isnan implementations are not constexpr)
static_assert(__builtin_isnan(bit_cast<double>(0x7FF0000000000001)));
static_assert(__builtin_isnan(bit_cast<double>(0xFFF0000000040000)));
// This means we can use all of these NaNs to store all other options for Value.
// To make sure all of these other representations we use 0x7FF8 as the base top
// 2 bytes which ensures the value is always a NaN.