[cxx-interop] Document guarantees and assumptions for SWIFT_SHARED_REFERENCE types passed to a C++ API as a parameter from Swift
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@egorzhdan @fahadnayyar Is this PR ready to be merged? |
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@shahmishal no, not yet. |
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Do we still plan to merge this? |
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SWIFT_SHARED_REFERENCE types passed to a C++ API from Swift
…hared references passed to a C++ API from Swift
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Yes @hnrklssn. We believe these are crucial aspects to document. After Swift 6.2, documenting assumptions about |
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@Xazax-hun @j-hui can you also please take a look at this? |
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SWIFT_SHARED_REFERENCE types passed to a C++ API from SwiftSWIFT_SHARED_REFERENCE types passed to a C++ API from Swift
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SWIFT_SHARED_REFERENCE types passed to a C++ API from SwiftSWIFT_SHARED_REFERENCE types passed to a C++ API as a parameter from Swift
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| The C++ function can overwrite the value of the argument with the new value. | ||
| However, the C++ function is responsible for releasing the old value, and ensuring that the new value is properly retained so that the Swift caller has ownership of the new value when the function returns. | ||
| Adhering to these rules is necessary to safely and correctly pass around `SWIFT_SHARED_REFERENCE` between Swift and C++. |
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@j-hui these 2 last lines are good, but I am not sure about their placement. Any suggestions?
Since we are editing this document with multiple calling conventions and rules about safely using SWIFT_SHARED_REFERENCE types and passing across the boundaries, I am not sure where to place these 2 lines.
Or maybe we can do such minor palcement edits later in a follow up patch?
These assumptions and guarantees are important to be documented to make sure that when C++ Shared Reference Types are passed as a non-const parameter to a C++ function or method from swift, then user's don't make wrong assumptions about the default behaviour supported in the Swift compiler.