New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

[SR-12430] self in Property Wrapper Using Enclosing Self Escapes Before Initialization Completed #54869

Closed

swift-ci opened this issue Mar 27, 2020 · 6 comments

Labels

accepts invalid bug compiler property wrappers

Collaborator

swift-ci commented Mar 27, 2020


Previous ID	SR-12430
Radar	None
Original Reporter	briantkelley (JIRA User)
Type	Bug
Status	Closed
Resolution	Done

Attachment: Download

Environment

macOS 10.15.4/Xcode 10.4

Also reproduces from trunk build at 3b3eade

Additional Detail from JIRA


Votes	0
Component/s	Compiler
Labels	Bug, AcceptsInvalid, PropertyWrappers
Assignee	briantkelley (JIRA)
Priority	Medium

md5: b9f06e7a94b959281ac36fd796a2e6c3

duplicates:

SR-12341 @propertyWrapper wrong behaviour

Issue Description:

In the attached sample code, self can be used to access uninitialized memory.

init(value: String) {
    self.value = value
}

@Notifying({ (p: Publisher, l: Listener) in l.propertyChanged(p) })
var value: String = ""

Where @Notifying is a property wrapper that uses the static subscript to access the enclosing self.

As a work around, the user can explicitly insert super.init():

init(value: String) {
    super.init()
    self.value = value
}

The Swift compiler should diagnose this scenario and emit an error diagnostic.

The text was updated successfully, but these errors were encountered:

Collaborator Author

swift-ci commented Mar 28, 2020

Comment by Brian T. Kelley (JIRA)

It looks like there's a special case for property wrappers in ElementUseCollector::collectClassSelfUses():

if (auto *PAI = dyn_cast<PartialApplyInst>(User)) {
  if (onlyUsedByAssignByWrapper(PAI))
    continue;
  Kind = DIUseKind::Escape;
}

Where onlyUsedByAssignByWrapper() doesn't consider if the property wrapper is using the wrappedValue computed property or static subscript which access to self.

Collaborator Author

swift-ci commented Mar 31, 2020

Comment by Brian T. Kelley (JIRA)

Collaborator Author

swift-ci commented May 28, 2020

Comment by Brian T. Kelley (JIRA)

The issue was fixed by 3aabdb5 in in PR #31248.

Collaborator Author

swift-ci commented May 28, 2020

Comment by Brian T. Kelley (JIRA)

There are still some corner cases where the compiler accepts invalid code so I'm re-opening.

Collaborator Author

swift-ci commented Sep 4, 2020

Comment by Brian T. Kelley (JIRA)

With the Swift compiler available in Xcode 12, Beta 6, I can no longer cause undefined behavior by accessing an object before it's initialized. However, now the class initializer does not differentiate between uninitialized and initialized so setting the property via the wrapper multiple times in an initializer can leak resources. That's a separate bug, however, so I'm closing this one.

Collaborator Author

swift-ci commented Sep 4, 2020

Comment by Brian T. Kelley (JIRA)

New issue documented in SR-13495.

swift-ci transferred this issue from apple/swift-issues

This issue was closed.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment