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Merged
merged 2 commits into from
Apr 9, 2025
Merged

Don't use a class to store the current exit test. #1065

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58d6f8c
Don't use a class to store the current exit test.
grynspan Apr 8, 2025
72bb403
Avoid thread-unsafe yielding of the current exit test
grynspan Apr 9, 2025
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50 changes: 28 additions & 22 deletions Sources/Testing/ExitTests/ExitTest.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -107,31 +107,34 @@ public struct ExitTest: Sendable, ~Copyable {
_observedValues = newValue
}
}

/// Make a copy of this instance.
///
/// - Returns: A copy of this instance.
///
/// This function is unsafe because if the caller is not careful, it could
/// invoke the same exit test twice.
fileprivate borrowing func unsafeCopy() -> Self {
var result = Self(id: id, body: body)
result._observedValues = _observedValues
return result
}
}

#if !SWT_NO_EXIT_TESTS
// MARK: - Current

@_spi(Experimental)
extension ExitTest {
/// A container type to hold the current exit test.
///
/// This class is temporarily necessary until `ManagedBuffer` is updated to
/// support storing move-only values. For more information, see [SE-NNNN](https://github.com/swiftlang/swift-evolution/pull/2657).
private final class _CurrentContainer: Sendable {
/// The exit test represented by this container.
///
/// The value of this property must be optional to avoid a copy when reading
/// the value in ``ExitTest/current``.
let exitTest: ExitTest?

init(exitTest: borrowing ExitTest) {
self.exitTest = ExitTest(id: exitTest.id, body: exitTest.body, _observedValues: exitTest._observedValues)
}
}

/// Storage for ``current``.
private static let _current = Locked<_CurrentContainer?>()
///
/// A pointer is used for indirection because `ManagedBuffer` cannot yet hold
/// move-only types.
private static nonisolated(unsafe) var _current: Locked<UnsafeMutablePointer<ExitTest?>> = {
let current = UnsafeMutablePointer<ExitTest?>.allocate(capacity: 1)
current.initialize(to: nil)
return Locked(rawValue: current)
}()

/// The exit test that is running in the current process, if any.
///
Expand All @@ -144,11 +147,13 @@ extension ExitTest {
/// process.
public static var current: ExitTest? {
_read {
if let current = _current.rawValue {
yield current.exitTest
} else {
yield nil
// NOTE: Even though this accessor is `_read` and has borrowing semantics,
// we must make a copy so that we don't yield lock-guarded memory to the
// caller (which is not concurrency-safe.)
let currentCopy = _current.withLock { current in
return current.pointee?.unsafeCopy()
}
yield currentCopy
}
}
}
Expand Down Expand Up @@ -235,7 +240,8 @@ extension ExitTest {

// Set ExitTest.current before the test body runs.
Self._current.withLock { current in
current = _CurrentContainer(exitTest: self)
precondition(current.pointee == nil, "Set the current exit test twice in the same process. Please file a bug report at https://github.com/swiftlang/swift-testing/issues/new")
current.pointee = self.unsafeCopy()
}

do {
Expand Down
4 changes: 2 additions & 2 deletions Sources/Testing/Support/Locked.swift
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Expand Up @@ -88,7 +88,7 @@ struct LockedWith<L, T>: RawRepresentable where L: Lockable {
/// This function can be used to synchronize access to shared data from a
/// synchronous caller. Wherever possible, use actor isolation or other Swift
/// concurrency tools.
nonmutating func withLock<R>(_ body: (inout T) throws -> R) rethrows -> R {
nonmutating func withLock<R>(_ body: (inout T) throws -> R) rethrows -> R where R: ~Copyable {
try _storage.withUnsafeMutablePointers { rawValue, lock in
L.unsafelyAcquireLock(at: lock)
defer {
Expand Down Expand Up @@ -118,7 +118,7 @@ struct LockedWith<L, T>: RawRepresentable where L: Lockable {
/// - Warning: Callers that unlock the lock _must_ lock it again before the
/// closure returns. If the lock is not acquired when `body` returns, the
/// effect is undefined.
nonmutating func withUnsafeUnderlyingLock<R>(_ body: (UnsafeMutablePointer<L>, T) throws -> R) rethrows -> R {
nonmutating func withUnsafeUnderlyingLock<R>(_ body: (UnsafeMutablePointer<L>, T) throws -> R) rethrows -> R where R: ~Copyable {
try withLock { value in
try _storage.withUnsafeMutablePointerToElements { lock in
try body(lock, value)
Expand Down