Fix overflow traps in DispatchTime/DispatchWallTime/DispatchTimeInterval #301
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moiseev
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Sep 15, 2017
| // Because of the way this function is used, we can always assume | ||
| // that m2 > 0. | ||
| private func clampedInt64Product(_ m1: Int64, _ m2: Int64) -> Int64 { | ||
| assert(m2 > 0, "multiplier must be positive") |
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assert is a noop in release builds. Should perhaps use _precondition?
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Not having the check in release builds is exactly what I want. The only calls to this method are internal to this file and the intent is only to document the assumption and to catch (admittedly unlikely) future changes that violate it.
src/swift/Time.swift
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| private func clampedInt64Product(_ m1: Int64, _ m2: Int64) -> Int64 { | ||
| assert(m2 > 0, "multiplier must be positive") | ||
| let (result, overflow) = m1.multipliedReportingOverflow(by: m2) | ||
| guard overflow == false else { |
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This reads a little backwards to me. What do you think about the following instead?
if overflow {
return m1 > 0 ? Int64,max : Int64.min
}
return result
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daagaak
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Sep 20, 2017
mwwa
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Sep 20, 2017
…val. rdar://problem/34440944
ktopley-apple
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Dec 6, 2018
Fix overflow traps in DispatchTime/DispatchWallTime/DispatchTimeInterval Signed-off-by: Daniel A. Steffen <dsteffen@apple.com>
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This is the swift-corelibs-libdispatch version of the PR at swiftlang/swift#11927.
Fixes overflows in DispatchTime/DispatchWallTime/DispatchTimeInterval.
Examples:
DispatchTime.now() + Date.distantFuture.timeIntervalSinceNow // traps
DispatchTime.now() + Date.distantPast.timeIntervalSinceNow. // traps
let t = DispatchTimeInterval.seconds(Int.max)
t == t // Traps due to conversion to nanoseconds.
rdar://problem/34440944