[6.2][cxx-interop] Basic support for anonymous structs with non-copyable fields #84120
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…ble fields Explanation: Anonymous structs cannot be copied or moved, these operations only can happen to their enclosing non-anonymous types. Stop trying to emit special member functions and value witness tables for these structs. This fix is required to unblock a high priority libc++ change that fixes an unintended ABI break. Issues: rdar://159928354 Original PRs: swiftlang#84105 Risk: Medium. I believe this is the right change but hard to anticipate if something depends on the presence of these operations (which is likely to be a bug). But this is required to unblock an important libc++ fix. Testing: Added a compiler test. Reviewers: @rjmccall
Xazax-hun
added
c++ interop
DougGregor
reviewed
Sep 5, 2025
lib/IRGen/GenMeta.cpp
Outdated
| if (auto cd = Target->getClangDecl()) | ||
| if (auto rd = dyn_cast<clang::RecordDecl>(cd)) | ||
| if (rd->isAnonymousStructOrUnion()) | ||
| return; |
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This early return is going to mean that the builder has the wrong size for the data structure. If we must handle things at this level (rather than, say, making emitValueWitnessTable put in stubs for the special member functions for such types). Worst case we could add a null here or a dummy symbol.
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Added a null here to preserve the size while talking about the stubs offline.
…data [cxx-interop] Make the size of anonymous types metadata is unchanged
…types [cxx-interop] Restrict the uses of anonymous types
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@swift-ci please test |
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Updated with some follow-up PRs to not generate reflection for anonymous fields and disallow referring to them directly. |
DougGregor
approved these changes
Sep 12, 2025
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Explanation: Anonymous structs cannot be copied or moved, these operations only can happen to their enclosing non-anonymous types. Stop trying to emit special member functions and value witness tables for these structs. This fix is required to unblock a high priority libc++ change that fixes an unintended ABI break.
Issues: rdar://159928354
Original PRs: #84105, #84152, #84199
Risk: Medium. I believe this is the right change but hard to anticipate if something depends on the presence of these operations (which is likely to be a bug). But this is required to unblock an important libc++ fix.
Testing: Added a compiler test.
Reviewers: @rjmccall