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LibJS: Add spec comments to Value::to_u32()

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This commit is contained in:
Linus Groh 2022-12-10 00:01:18 +00:00
parent f958b19b19
commit 1ef2b43e4c
Notes: sideshowbarker 2024-07-17 18:46:30 +09:00 
Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/1ef2b43e4c
Pull-request: https://github.com/SerenityOS/serenity/pull/16405
Reviewed-by: https://github.com/davidot ✅
1 changed files with 13 additions and 4 deletions
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17
Userland/Libraries/LibJS/Runtime/Value.cpp
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@ -909,13 +909,22 @@ ThrowCompletionOr<i32> Value::to_i32(VM& vm) const
// 7.1.7 ToUint32 ( argument ), https://tc39.es/ecma262/#sec-touint32
ThrowCompletionOr<u32> Value::to_u32(VM& vm) const
{
double value = TRY(to_number(vm)).as_double();
if (!isfinite(value) || value == 0)
// 1. Let number be ? ToNumber(argument).
double number = TRY(to_number(vm)).as_double();
// 2. If number is not finite or number is either +0𝔽 or -0𝔽, return +0𝔽.
if (!isfinite(number) || number == 0)
return 0;
auto int_val = floor(fabs(value));
if (signbit(value))
// 3. Let int be the mathematical value whose sign is the sign of number and whose magnitude is floor(abs(ℝ(number))).
auto int_val = floor(fabs(number));
if (signbit(number))
int_val = -int_val;
// 4. Let int32bit be int modulo 2^32.
auto int32bit = fmod(int_val, NumericLimits<u32>::max() + 1.0);
// 5. Return 𝔽(int32bit).
// Cast to i64 here to ensure that the double --> u32 cast doesn't invoke undefined behavior
// Otherwise, negative numbers cause a UBSAN warning.
return static_cast<u32>(static_cast<i64>(int32bit));