🍒[cxx-interop] Zero-initialize C++ structs when calling their default constructors #73076
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…constructors When Swift imports C structs, it synthesizes an initializer that takes no arguments and zero-initializes the C struct. When C++ interop is enabled, Clang treats all C structs as if they were C++ structs. This means that some of the C structs will get a default constructor implicitly generated by Clang. This implicit default constructor will not zero-initialize trivial fields of the struct. This is a common source of confusion and subtle bugs for developers who try to enable C++ interop in existing projects that use C interop and rely on zero-initialization of C structs. rdar://115909532 (cherry picked from commit bac5d0e)
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@swift-ci please test |
DougGregor
approved these changes
Apr 17, 2024
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Explanation: When Swift imports C structs, it synthesizes an initializer that takes no arguments and zero-initializes the C struct. However, when C++ interop is enabled, the structs were not zero-initialized.
Scope: IRGen of C++ constructors.
Risk: Low, this only takes effect when C++ interop is enabled.
Testing: Added a compiler test.
Issue: rdar://115909532
Reviewer: @beccadax @aschwaighofer
Original PR: #72903
(cherry picked from commit bac5d0e)