[cxx-interop] Add RETURNS_RETAINED annotations to C++ thunks#88597
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patrykstefanski wants to merge 1 commit intoswiftlang:mainfrom
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[cxx-interop] Add RETURNS_RETAINED annotations to C++ thunks#88597patrykstefanski wants to merge 1 commit intoswiftlang:mainfrom
patrykstefanski wants to merge 1 commit intoswiftlang:mainfrom
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Swift functions exposed to C++ return +1 (retained) values, but the generated C++ thunks in the -Swift.h header lacked ownership annotations. This prevented Clang's static analyzer from verifying reference counts when C++ code calls into Swift. Add NS_RETURNS_RETAINED, CF_RETURNS_RETAINED, and SWIFT_RETURNS_RETAINED annotations to thunk signatures based on the return type: - NS_RETURNS_RETAINED for ObjC classes (NSString, etc.) and existentials (id) - CF_RETURNS_RETAINED for CF types (CFString, etc.) - SWIFT_RETURNS_RETAINED for foreign reference types rdar://165231653
patrykstefanski
requested review from
Xazax-hun,
egorzhdan,
hnrklssn,
j-hui and
susmonteiro
j-hui
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Apr 21, 2026
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j-hui
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This LGTM!
Just wondering, is there ever a need to print a RETURNS_UNRETAINED annotation?
hnrklssn
reviewed
Apr 22, 2026
| // CHECK: #if !defined(CF_RETURNS_RETAINED) | ||
| // CHECK: #if !defined(SWIFT_RETURNS_RETAINED) | ||
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| // CHECK: SWIFT_INLINE_THUNK NSString *_Nonnull getName() |
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It looks like these are emitted in alphabetical order. WDYT about flipping the naming scheme so it's swiftClassReturn, swiftClassPassthrough, methodGetNSString etc? That way you can keep them grouped by category, but sort the decls in alphabetical order and place the check comments right next to the decl being checked.
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I think that's a great idea! I'll do it
Xazax-hun
approved these changes
Apr 22, 2026
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| // A function returning NSString? generates a thunk returning `NSString | ||
| // *_Nullable`. | ||
| Type unwrapped = resultTy->getOptionalObjectType(); |
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Nit: could this be simplified via lookThroughSingleOptionalType?
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Swift functions exposed to C++ return +1 (retained) values, but the generated C++ thunks in the -Swift.h header lacked ownership annotations. This prevented Clang's static analyzer from verifying reference counts when C++ code calls into Swift.
Add NS_RETURNS_RETAINED, CF_RETURNS_RETAINED, and SWIFT_RETURNS_RETAINED annotations to thunk signatures based on the return type:
rdar://165231653