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GeezerVison is showing github.com — Assert that `JSObject` is being accessed only from the owner thread · sakrist/JavaScriptKit@45206f7

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  • Package.swift
  • Sources/JavaScriptKit
    • FundamentalObjects
      • JSObject.swift
    • ThreadLocal.swift
  • Tests/JavaScriptKitTests
    • ThreadLocalTests.swift
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‎Package.swift‎

Copy file name to clipboardExpand all lines: Package.swift
+5Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -58,6 +58,11 @@ let package = Package(
5858
]
5959
),
6060
.target(name: "_CJavaScriptEventLoopTestSupport"),
61+
62+
.testTarget(
63+
name: "JavaScriptKitTests",
64+
dependencies: ["JavaScriptKit"]
65+
),
6166
.testTarget(
6267
name: "JavaScriptEventLoopTestSupportTests",
6368
dependencies: [
Collapse file

‎Sources/JavaScriptKit/FundamentalObjects/JSObject.swift‎

Copy file name to clipboardExpand all lines: Sources/JavaScriptKit/FundamentalObjects/JSObject.swift
+82-14Lines changed: 82 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,11 @@
11
import _CJavaScriptKit
22

3+
#if canImport(wasi_pthread)
4+
import wasi_pthread
5+
#else
6+
import Foundation // for pthread_t on non-wasi platforms
7+
#endif
8+
39
/// `JSObject` represents an object in JavaScript and supports dynamic member lookup.
410
/// Any member access like `object.foo` will dynamically request the JavaScript and Swift
511
/// runtime bridge library for a member with the specified name in this object.
@@ -18,9 +24,35 @@ import _CJavaScriptKit
1824
public class JSObject: Equatable {
1925
@_spi(JSObject_id)
2026
public var id: JavaScriptObjectRef
27+
28+
#if _runtime(_multithreaded)
29+
private let ownerThread: pthread_t
30+
#endif
31+
2132
@_spi(JSObject_id)
2233
public init(id: JavaScriptObjectRef) {
2334
self.id = id
35+
self.ownerThread = pthread_self()
36+
}
37+
38+
/// Asserts that the object is being accessed from the owner thread.
39+
///
40+
/// - Parameter hint: A string to provide additional context for debugging.
41+
///
42+
/// NOTE: Accessing a `JSObject` from a thread other than the thread it was created on
43+
/// is a programmer error and will result in a runtime assertion failure because JavaScript
44+
/// object spaces are not shared across threads backed by Web Workers.
45+
private func assertOnOwnerThread(hint: @autoclosure () -> String) {
46+
#if _runtime(_multithreaded)
47+
precondition(pthread_equal(ownerThread, pthread_self()) != 0, "JSObject is being accessed from a thread other than the owner thread: \(hint())")
48+
#endif
49+
}
50+
51+
/// Asserts that the two objects being compared are owned by the same thread.
52+
private static func assertSameOwnerThread(lhs: JSObject, rhs: JSObject, hint: @autoclosure () -> String) {
53+
#if _runtime(_multithreaded)
54+
precondition(pthread_equal(lhs.ownerThread, rhs.ownerThread) != 0, "JSObject is being accessed from a thread other than the owner thread: \(hint())")
55+
#endif
2456
}
2557

2658
#if !hasFeature(Embedded)
@@ -79,32 +111,56 @@ public class JSObject: Equatable {
79111
/// - Parameter name: The name of this object's member to access.
80112
/// - Returns: The value of the `name` member of this object.
81113
public subscript(_ name: String) -> JSValue {
82-
get { getJSValue(this: self, name: JSString(name)) }
83-
set { setJSValue(this: self, name: JSString(name), value: newValue) }
114+
get {
115+
assertOnOwnerThread(hint: "reading '\(name)' property")
116+
return getJSValue(this: self, name: JSString(name))
117+
}
118+
set {
119+
assertOnOwnerThread(hint: "writing '\(name)' property")
120+
setJSValue(this: self, name: JSString(name), value: newValue)
121+
}
84122
}
85123

86124
/// Access the `name` member dynamically through JavaScript and Swift runtime bridge library.
87125
/// - Parameter name: The name of this object's member to access.
88126
/// - Returns: The value of the `name` member of this object.
89127
public subscript(_ name: JSString) -> JSValue {
90-
get { getJSValue(this: self, name: name) }
91-
set { setJSValue(this: self, name: name, value: newValue) }
128+
get {
129+
assertOnOwnerThread(hint: "reading '<<JSString>>' property")
130+
return getJSValue(this: self, name: name)
131+
}
132+
set {
133+
assertOnOwnerThread(hint: "writing '<<JSString>>' property")
134+
setJSValue(this: self, name: name, value: newValue)
135+
}
92136
}
93137

94138
/// Access the `index` member dynamically through JavaScript and Swift runtime bridge library.
95139
/// - Parameter index: The index of this object's member to access.
96140
/// - Returns: The value of the `index` member of this object.
97141
public subscript(_ index: Int) -> JSValue {
98-
get { getJSValue(this: self, index: Int32(index)) }
99-
set { setJSValue(this: self, index: Int32(index), value: newValue) }
142+
get {
143+
assertOnOwnerThread(hint: "reading '\(index)' property")
144+
return getJSValue(this: self, index: Int32(index))
145+
}
146+
set {
147+
assertOnOwnerThread(hint: "writing '\(index)' property")
148+
setJSValue(this: self, index: Int32(index), value: newValue)
149+
}
100150
}
101151

102152
/// Access the `symbol` member dynamically through JavaScript and Swift runtime bridge library.
103153
/// - Parameter symbol: The name of this object's member to access.
104154
/// - Returns: The value of the `name` member of this object.
105155
public subscript(_ name: JSSymbol) -> JSValue {
106-
get { getJSValue(this: self, symbol: name) }
107-
set { setJSValue(this: self, symbol: name, value: newValue) }
156+
get {
157+
assertOnOwnerThread(hint: "reading '<<JSSymbol>>' property")
158+
return getJSValue(this: self, symbol: name)
159+
}
160+
set {
161+
assertOnOwnerThread(hint: "writing '<<JSSymbol>>' property")
162+
setJSValue(this: self, symbol: name, value: newValue)
163+
}
108164
}
109165

110166
#if !hasFeature(Embedded)
@@ -134,7 +190,8 @@ public class JSObject: Equatable {
134190
/// - Parameter constructor: The constructor function to check.
135191
/// - Returns: The result of `instanceof` in the JavaScript environment.
136192
public func isInstanceOf(_ constructor: JSFunction) -> Bool {
137-
swjs_instanceof(id, constructor.id)
193+
assertOnOwnerThread(hint: "calling 'isInstanceOf'")
194+
return swjs_instanceof(id, constructor.id)
138195
}
139196

140197
static let _JS_Predef_Value_Global: JavaScriptObjectRef = 0
@@ -145,21 +202,32 @@ public class JSObject: Equatable {
145202

146203
// `JSObject` storage itself is immutable, and use of `JSObject.global` from other
147204
// threads maintains the same semantics as `globalThis` in JavaScript.
148-
#if compiler(>=5.10)
149-
nonisolated(unsafe)
150-
static let _global = JSObject(id: _JS_Predef_Value_Global)
205+
#if _runtime(_multithreaded)
206+
@LazyThreadLocal(initialize: {
207+
return JSObject(id: _JS_Predef_Value_Global)
208+
})
209+
private static var _global: JSObject
151210
#else
152-
static let _global = JSObject(id: _JS_Predef_Value_Global)
211+
#if compiler(>=5.10)
212+
nonisolated(unsafe)
213+
static let _global = JSObject(id: _JS_Predef_Value_Global)
214+
#else
215+
static let _global = JSObject(id: _JS_Predef_Value_Global)
216+
#endif
153217
#endif
154218

155-
deinit { swjs_release(id) }
219+
deinit {
220+
assertOnOwnerThread(hint: "deinitializing")
221+
swjs_release(id)
222+
}
156223

157224
/// Returns a Boolean value indicating whether two values point to same objects.
158225
///
159226
/// - Parameters:
160227
/// - lhs: A object to compare.
161228
/// - rhs: Another object to compare.
162229
public static func == (lhs: JSObject, rhs: JSObject) -> Bool {
230+
assertSameOwnerThread(lhs: lhs, rhs: rhs, hint: "comparing two JSObjects for equality")
163231
return lhs.id == rhs.id
164232
}
165233

Collapse file

‎Sources/JavaScriptKit/ThreadLocal.swift‎

Copy file name to clipboard
+103Lines changed: 103 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,103 @@
1+
#if _runtime(_multithreaded)
2+
#if canImport(wasi_pthread)
3+
import wasi_pthread
4+
#elseif canImport(Darwin)
5+
import Darwin
6+
#elseif canImport(Glibc)
7+
import Glibc
8+
#else
9+
#error("Unsupported platform")
10+
#endif
11+
12+
@propertyWrapper
13+
final class ThreadLocal<Value>: Sendable {
14+
var wrappedValue: Value? {
15+
get {
16+
guard let pointer = pthread_getspecific(key) else {
17+
return nil
18+
}
19+
return fromPointer(pointer)
20+
}
21+
set {
22+
if let oldPointer = pthread_getspecific(key) {
23+
release(oldPointer)
24+
}
25+
if let newValue = newValue {
26+
let pointer = toPointer(newValue)
27+
pthread_setspecific(key, pointer)
28+
}
29+
}
30+
}
31+
32+
private let key: pthread_key_t
33+
private let toPointer: @Sendable (Value) -> UnsafeMutableRawPointer
34+
private let fromPointer: @Sendable (UnsafeMutableRawPointer) -> Value
35+
private let release: @Sendable (UnsafeMutableRawPointer) -> Void
36+
37+
init() where Value: AnyObject {
38+
var key = pthread_key_t()
39+
pthread_key_create(&key, nil)
40+
self.key = key
41+
self.toPointer = { Unmanaged.passRetained($0).toOpaque() }
42+
self.fromPointer = { Unmanaged<Value>.fromOpaque($0).takeUnretainedValue() }
43+
self.release = { Unmanaged<Value>.fromOpaque($0).release() }
44+
}
45+
46+
class Box {
47+
let value: Value
48+
init(_ value: Value) {
49+
self.value = value
50+
}
51+
}
52+
53+
init(boxing _: Void) {
54+
var key = pthread_key_t()
55+
pthread_key_create(&key, nil)
56+
self.key = key
57+
self.toPointer = {
58+
let box = Box($0)
59+
let pointer = Unmanaged.passRetained(box).toOpaque()
60+
return pointer
61+
}
62+
self.fromPointer = {
63+
let box = Unmanaged<Box>.fromOpaque($0).takeUnretainedValue()
64+
return box.value
65+
}
66+
self.release = { Unmanaged<Box>.fromOpaque($0).release() }
67+
}
68+
69+
deinit {
70+
if let oldPointer = pthread_getspecific(key) {
71+
release(oldPointer)
72+
}
73+
pthread_key_delete(key)
74+
}
75+
}
76+
77+
@propertyWrapper
78+
final class LazyThreadLocal<Value>: Sendable {
79+
private let storage: ThreadLocal<Value>
80+
81+
var wrappedValue: Value {
82+
if let value = storage.wrappedValue {
83+
return value
84+
}
85+
let value = initialValue()
86+
storage.wrappedValue = value
87+
return value
88+
}
89+
90+
private let initialValue: @Sendable () -> Value
91+
92+
init(initialize: @Sendable @escaping () -> Value) where Value: AnyObject {
93+
self.storage = ThreadLocal()
94+
self.initialValue = initialize
95+
}
96+
97+
init(initialize: @Sendable @escaping () -> Value) {
98+
self.storage = ThreadLocal(boxing: ())
99+
self.initialValue = initialize
100+
}
101+
}
102+
103+
#endif
Collapse file

‎Tests/JavaScriptKitTests/ThreadLocalTests.swift‎

Copy file name to clipboard
+34Lines changed: 34 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,34 @@
1+
import XCTest
2+
@testable import JavaScriptKit
3+
4+
final class ThreadLocalTests: XCTestCase {
5+
class MyHeapObject {}
6+
7+
func testLeak() throws {
8+
struct Check {
9+
@ThreadLocal
10+
var value: MyHeapObject?
11+
}
12+
weak var weakObject: MyHeapObject?
13+
do {
14+
let object = MyHeapObject()
15+
weakObject = object
16+
let check = Check()
17+
check.value = object
18+
XCTAssertNotNil(check.value)
19+
XCTAssertTrue(check.value === object)
20+
}
21+
XCTAssertNil(weakObject)
22+
}
23+
24+
func testLazyThreadLocal() throws {
25+
struct Check {
26+
@LazyThreadLocal(initialize: { MyHeapObject() })
27+
var value: MyHeapObject
28+
}
29+
let check = Check()
30+
let object1 = check.value
31+
let object2 = check.value
32+
XCTAssertTrue(object1 === object2)
33+
}
34+
}

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