[cxx-interop] Mark C++ reference parameters @Addressable

C++ code can return values that depend on the storage that backs the references that were passed in as argument. Thus, swift should not introdue temporary copies of that storage before invoking those functions as they could result in lifetime issues.
swiftlang · Jan 20, 2025 · e3b229f · e3b229f
1 parent 6b2fb2e
commit e3b229f
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Showing 3 changed files with 31 additions and 2 deletions.
diff --git a/lib/ClangImporter/ImportDecl.cpp b/lib/ClangImporter/ImportDecl.cpp
@@ -3891,6 +3891,9 @@ namespace {
           }
           if (selfIdx) {
             func->setSelfIndex(selfIdx.value());
+            if (func->getASTContext().LangOpts.hasFeature(
+                    Feature::AddressableParameters))
+              func->getImplicitSelfDecl()->setAddressable();
           } else {
             func->setStatic();
             func->setImportAsStaticMember();

diff --git a/lib/ClangImporter/ImportType.cpp b/lib/ClangImporter/ImportType.cpp
@@ -2676,17 +2676,25 @@ static ParamDecl *getParameterInfo(ClangImporter::Implementation *impl,
       impl->importSourceLoc(param->getLocation()), bodyName,
       impl->ImportedHeaderUnit);
 
+  auto &ASTContext = paramInfo->getASTContext();
   // If SendingArgsAndResults are enabled and we have a sending argument,
   // set that the param was sending.
-  if (paramInfo->getASTContext().LangOpts.hasFeature(
-          Feature::SendingArgsAndResults)) {
+  if (ASTContext.LangOpts.hasFeature(Feature::SendingArgsAndResults)) {
     if (auto *attr = param->getAttr<clang::SwiftAttrAttr>()) {
       if (attr->getAttribute() == "sending") {
         paramInfo->setSending();
       }
     }
   }
 
+  // C++ types taking a reference might return a reference/pointer to a
+  // subobject of the referenced storage. In those cases we need to prevent the
+  // Swift compiler to pass in a temporary copy to prevent dangling.
+  if (ASTContext.LangOpts.hasFeature(Feature::AddressableParameters) &&
+      !param->getType().isNull() && param->getType()->isReferenceType()) {
+    paramInfo->setAddressable();
+  }
+
   // Foreign references are already references so they don't need to be passed
   // as inout.
   paramInfo->setSpecifier(

diff --git a/test/Interop/Cxx/class/nonescapable-lifetimebound.swift b/test/Interop/Cxx/class/nonescapable-lifetimebound.swift
@@ -1,8 +1,11 @@
 // RUN: rm -rf %t
 // RUN: split-file %s %t
 // RUN: %target-swift-frontend -I %swift_src_root/lib/ClangImporter/SwiftBridging  -I %t/Inputs -emit-sil %t/test.swift -enable-experimental-feature LifetimeDependence -cxx-interoperability-mode=default -diagnostic-style llvm 2>&1 | %FileCheck %s
+// RUN: %target-swift-frontend -I %swift_src_root/lib/ClangImporter/SwiftBridging  -I %t/Inputs -emit-sil %t/test.swift  -enable-experimental-feature AddressableParameters -enable-experimental-feature LifetimeDependence -cxx-interoperability-mode=default -diagnostic-style llvm 2>&1 | %FileCheck %s -check-prefix=CHECK-ADDRESSABLE
 // RUN: not %target-swift-frontend -I %swift_src_root/lib/ClangImporter/SwiftBridging  -I %t/Inputs -emit-sil %t/test.swift -cxx-interoperability-mode=default -diagnostic-style llvm 2>&1 | %FileCheck %s -check-prefix=CHECK-NO-LIFETIMES
 
+// REQUIRES: swift_feature_AddressableParameters
+// REQUIRES: swift_feature_LifetimeDependence
 
 //--- Inputs/module.modulemap
 module Test {
@@ -120,6 +123,21 @@ CaptureView getCaptureView(const Owner& owner [[clang::lifetimebound]]) {
 // CHECK: sil [clang CaptureView.captureView] {{.*}} : $@convention(cxx_method) (View, @lifetime(copy 0) @inout CaptureView) -> ()
 // CHECK: sil [clang CaptureView.handOut] {{.*}} : $@convention(cxx_method) (@lifetime(copy 1) @inout View, @in_guaranteed CaptureView) -> ()
 
+// CHECK-ADDRESSABLE: sil [clang makeOwner] {{.*}}: $@convention(c) () -> Owner
+// CHECK-ADDRESSABLE: sil [clang getView] {{.*}} : $@convention(c) (@in_guaranteed Owner) -> @lifetime(borrow 0) @owned View
+// CHECK-ADDRESSABLE: sil [clang getViewFromFirst] {{.*}} : $@convention(c) (@in_guaranteed Owner, @in_guaranteed Owner) -> @lifetime(borrow 0) @owned View
+// CHECK-ADDRESSABLE: sil [clang getViewFromEither] {{.*}} : $@convention(c) (@in_guaranteed Owner, @in_guaranteed Owner) -> @lifetime(borrow 0, borrow 1) @owned View
+// CHECK-ADDRESSABLE: sil [clang Owner.handOutView] {{.*}} : $@convention(cxx_method) (@in_guaranteed Owner) -> @lifetime(borrow 0) @owned View
+// CHECK-ADDRESSABLE: sil [clang Owner.handOutView2] {{.*}} : $@convention(cxx_method) (View, @in_guaranteed Owner) -> @lifetime(borrow 1) @owned View
+// CHECK-ADDRESSABLE: sil [clang getViewFromEither] {{.*}} : $@convention(c) (@guaranteed View, @guaranteed View) -> @lifetime(copy 0, copy 1) @owned View
+// CHECK-ADDRESSABLE: sil [clang View.init] {{.*}} : $@convention(c) () -> @lifetime(immortal) @out View
+// CHECK-ADDRESSABLE: sil [clang OtherView.init] {{.*}} : $@convention(c) (@guaranteed View) -> @lifetime(copy 0) @out OtherView
+// CHECK-ADDRESSABLE: sil [clang returnsImmortal] {{.*}} : $@convention(c) () -> @lifetime(immortal) @owned View
+// CHECK-ADDRESSABLE: sil [clang copyView] {{.*}} : $@convention(c) (View, @lifetime(copy 0) @inout View) -> ()
+// CHECK-ADDRESSABLE: sil [clang getCaptureView] {{.*}} : $@convention(c) (@in_guaranteed Owner) -> @lifetime(borrow 0) @owned CaptureView
+// CHECK-ADDRESSABLE: sil [clang CaptureView.captureView] {{.*}} : $@convention(cxx_method) (View, @lifetime(copy 0) @inout CaptureView) -> ()
+// CHECK-ADDRESSABLE: sil [clang CaptureView.handOut] {{.*}} : $@convention(cxx_method) (@lifetime(copy 1) @inout View, @in_guaranteed CaptureView) -> ()
+
 // CHECK-NO-LIFETIMES: nonescapable.h:36:6: error: returning ~Escapable type requires '-enable-experimental-feature LifetimeDependence'
 // CHECK-NO-LIFETIMES: nonescapable.h:40:6: error: returning ~Escapable type requires '-enable-experimental-feature LifetimeDependence'
 // CHECK-NO-LIFETIMES: nonescapable.h:46:6: error: returning ~Escapable type requires '-enable-experimental-feature LifetimeDependence'