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[stdlib] Implement _copyContents on internal Array types

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`_copyContents(initializing:)` is a core method of Sequence, and it is used surprisingly often to copy stuff out of sequences. Array’s internal types currently have explicit implementations of it that trap (to prevent a performance bug due to the default iterator-based implementation. This has proved a bad idea, as not all code paths that end up calling `_copyContents` have actually been expunged — so we replaced a performance bug with a catastrophic correctness bug. 😥

Rather than trying to play whack-a-mole with code paths that end up in `_copyContents`, replace the traps with (relatively) efficient implementations, based on the ancient `_copyContents(subRange:initializing)` methods that have already been there all this time.

This resolves https://bugs.swift.org/browse/SR-14663.

I expect specialization will make this fix deploy back to earlier OSes in most (but unfortunately not all) cases.
This commit is contained in:
Karoy Lorentey
2021-06-14 22:05:37 -07:00
parent b001b0b33a
commit 466e26a872
8 changed files with 224 additions and 16 deletions
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69
test/stdlib/ArrayBridge.swift.gyb
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@@ -2,7 +2,7 @@
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
@@ -471,6 +471,8 @@ tests.test("testMutableArray") {
}
tests.test("rdar://problem/27905230") {
// Casting an NSArray to Array<Any> would trap because of an erroneous
// precondition.
let dict = RDar27905230.mutableDictionaryOfMutableLists()!
let arr = dict["list"]!
expectEqual(arr[0] as! NSNull, NSNull())
@@ -482,4 +484,69 @@ tests.test("rdar://problem/27905230") {
expectEqual(arr[5] as! Date, Date(timeIntervalSince1970: 0))
}
tests.test("verbatimBridged/Base/withUnsafeBufferPointer") {
let a = NSArray(array: [Base(0), Base(1), Base(2), Base(3)])
let b = a as! [Base]
let success: Bool = b.withUnsafeBufferPointer { buffer in
expectEqual(buffer.count, 4)
guard buffer.count == 4 else { return false }
expectEqual(buffer[0].value, 0)
expectEqual(buffer[1].value, 1)
expectEqual(buffer[2].value, 2)
expectEqual(buffer[3].value, 3)
return true
}
expectTrue(success)
}
// https://bugs.swift.org/browse/SR-14663
tests.test("verbatimBridged/AnyObject/withUnsafeBufferPointer") {
let a = NSArray(array: [Base(0), Base(1), Base(2), Base(3)])
let b = a as [AnyObject]
let success: Bool = b.withUnsafeBufferPointer { buffer in
expectEqual(buffer.count, 4)
guard buffer.count == 4 else { return false }
expectEqual((buffer[0] as? Base)?.value, 0)
expectEqual((buffer[1] as? Base)?.value, 1)
expectEqual((buffer[2] as? Base)?.value, 2)
expectEqual((buffer[3] as? Base)?.value, 3)
return true
}
expectTrue(success)
}
tests.test("verbatimBridged/Base/withUnsafeMutableBufferPointer") {
let a = NSArray(array: [Base(0), Base(1), Base(2), Base(3)])
var b = a as! [Base]
let success: Bool = b.withUnsafeMutableBufferPointer { buffer in
expectEqual(buffer.count, 4)
guard buffer.count == 4 else { return false }
expectEqual(buffer[0].value, 0)
expectEqual(buffer[1].value, 1)
expectEqual(buffer[2].value, 2)
expectEqual(buffer[3].value, 3)
buffer[0] = Base(4)
return true
}
expectTrue(success)
expectEqual(b[0].value, 4)
}
tests.test("verbatimBridged/AnyObject/withUnsafeMutableBufferPointer") {
let a = NSArray(array: [Base(0), Base(1), Base(2), Base(3)])
var b = a as [AnyObject]
let success: Bool = b.withUnsafeMutableBufferPointer { buffer in
expectEqual(buffer.count, 4)
guard buffer.count == 4 else { return false }
expectEqual((buffer[0] as? Base)?.value, 0)
expectEqual((buffer[1] as? Base)?.value, 1)
expectEqual((buffer[2] as? Base)?.value, 2)
expectEqual((buffer[3] as? Base)?.value, 3)
buffer[0] = Base(4)
return true
}
expectTrue(success)
expectEqual((b[0] as? Base)?.value, 4)
}
runAllTests()