🍒[cxx-interop] Fix runtime crash when casting from an existential to a foreign reference type #78238
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
… foreign reference type When a C++ foreign reference type is conformed to a Swift protocol via a Swift extension, trying to cast `any MyProtocol` to the foreign reference type crashes the runtime. This was because `selectCasterForDest` wasn't handling C++ foreign reference types, and we were hitting `swift_unreachable`. This change makes sure the runtime doesn't crash for such casts. Notably, Swift doesn't have enough metadata to determine if the conditional cast actually succeeded. This is also a problem for CF types. Casting CF types in a similar fashion triggers a typechecker diagnostic. That diagnostic will be amended in a follow-up patch to also trigger for foreign reference types. rdar://141227849 (cherry picked from commit 84ae5fb)
|
@swift-ci please test |
egorzhdan
changed the title
tbkka
approved these changes
Dec 17, 2024
DougGregor
approved these changes
Dec 17, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Explanation: When a C++ foreign reference type is conformed to a Swift protocol via a Swift extension, trying to cast
any MyProtocolto the foreign reference type crashes the runtime. This was becauseselectCasterForDestwasn't handling C++ foreign reference types, and we were hittingswift_unreachable.Scope: This changes the dynamic casting behavior for foreign reference types in the Swift runtime.
Risk: Low, this only changes a code path that is specific to foreign reference types.
Testing: Added compiler tests.
Issue: rdar://141227849
Reviewer: @mikeash @tbkka
Original PR: #78223