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[cxx-interop] Relax a SILVerifier assertion for immortal reference types #81614

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Merged
merged 1 commit into from
May 21, 2025
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[cxx-interop] Relax a SILVerifier assertion for immortal reference types #81614

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8 changes: 7 additions & 1 deletion lib/SIL/Verifier/SILVerifier.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1059,7 +1059,13 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {

auto objectTy = value->getType().unwrapOptionalType();

require(objectTy.isReferenceCounted(F.getModule()),
// Immortal C++ foreign reference types are represented as trivially lowered
// types since they do not require retain/release calls.
bool isImmortalFRT = objectTy.isForeignReferenceType() &&
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Is this also true for SWIFT_UNSAFE_REFERENCEs?

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Yeap! From the compiler point of view, they're the same thing, except if strictly safe mode is enabled – both SWIFT_UNSAFE_REFERENCE and SWIFT_IMMORTAL_REFERENCE macros expand into retain:immortal and release:immortal.

objectTy.getASTType()->getReferenceCounting() ==
ReferenceCounting::None;

require(objectTy.isReferenceCounted(F.getModule()) || isImmortalFRT,
valueDescription + " must have reference semantics");
}

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20 changes: 20 additions & 0 deletions test/Interop/Cxx/foreign-reference/unmanaged.swift
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@@ -0,0 +1,20 @@
// RUN: %target-run-simple-swift(-I %S/Inputs -cxx-interoperability-mode=default -Xfrontend -disable-availability-checking) | %FileCheck %s

// REQUIRES: executable_test

import POD

extension Empty {
public static func == (lhs: Empty, rhs: Empty) -> Bool {
Unmanaged.passUnretained(lhs).toOpaque() == Unmanaged.passUnretained(rhs).toOpaque()
}
}

let x = Empty.create()
let y = Empty.create()

print(x == y)
// CHECK: false

print(x == x)
// CHECK: true