[interop][SwiftToCxx] add support for passing class types to Swift functions

Author: hyp

lib/PrintAsClang/PrintClangClassType.cpp

@@ -73,6 +73,9 @@ void ClangClassTypePrinter::printClassTypeDecl(
         os << " makeRetained(void * _Nonnull ptr) noexcept { return ";
         printer.printBaseName(typeDecl);
         os << "(ptr); }\n";
+        os << "static inline void * _Nonnull getOpaquePointer(const ";
+        printer.printBaseName(typeDecl);
+        os << " &object) noexcept { return object._opaquePointer; }\n";
         os << "};\n";
       });
 }
@@ -89,3 +92,16 @@ void ClangClassTypePrinter::printClassTypeReturnScaffold(
   bodyPrinter();
   os << ");\n";
 }
+
+void ClangClassTypePrinter::printParameterCxxtoCUseScaffold(
+    raw_ostream &os, const ClassDecl *type, const ModuleDecl *moduleContext,
+    llvm::function_ref<void(void)> bodyPrinter, bool isInOut) {
+  // FIXME: Handle isInOut
+  ClangSyntaxPrinter(os).printModuleNamespaceQualifiersIfNeeded(
+      type->getModuleContext(), moduleContext);
+  os << cxx_synthesis::getCxxImplNamespaceName() << "::";
+  ClangValueTypePrinter::printCxxImplClassName(os, type);
+  os << "::getOpaquePointer(";
+  bodyPrinter();
+  os << ')';
+}

lib/PrintAsClang/PrintClangClassType.h

@@ -37,6 +37,10 @@ class ClangClassTypePrinter {
                                const ModuleDecl *moduleContext,
                                llvm::function_ref<void(void)> bodyPrinter);
 
+  static void printParameterCxxtoCUseScaffold(
+      raw_ostream &os, const ClassDecl *type, const ModuleDecl *moduleContext,
+      llvm::function_ref<void(void)> bodyPrinter, bool isInOut);
+
 private:
   raw_ostream &os;
 };

lib/PrintAsClang/PrintClangFunction.cpp

@@ -459,6 +459,12 @@ void DeclAndTypeClangFunctionPrinter::printCxxToCFunctionParameterUse(
       return;
     }
 
+    if (auto *classDecl = type->getClassOrBoundGenericClass()) {
+      ClangClassTypePrinter::printParameterCxxtoCUseScaffold(
+          os, classDecl, moduleContext, namePrinter, isInOut);
+      return;
+    }
+
     if (auto *decl = type->getNominalOrBoundGenericNominal()) {
       if ((isa<StructDecl>(decl) || isa<EnumDecl>(decl))) {
         ClangValueTypePrinter(os, cPrologueOS, typeMapping, interopContext)

test/Interop/SwiftToCxx/class/swift-class-execution.cpp

@@ -12,13 +12,44 @@
 
 #include <assert.h>
 #include "class.h"
+#include <cstdio>
+
+extern "C" size_t swift_retainCount(void * _Nonnull obj);
+
+size_t getRetainCount(const Class::ClassWithIntField & swiftClass) {
+    void *p = Class::_impl::_impl_ClassWithIntField::getOpaquePointer(swiftClass);
+    return swift_retainCount(p);
+}
 
 int main() {
   using namespace Class;
 
   // Ensure that the class is released.
-  auto x = returnClassWithIntField();
+  {
+    auto x = returnClassWithIntField();
+    assert(getRetainCount(x) == 1);
+  }
 // CHECK:      init ClassWithIntField
+// CHECK-NEXT: destroy ClassWithIntField
+    
+  {
+    auto x = returnClassWithIntField();
+    {
+      takeClassWithIntField(x);
+      assert(getRetainCount(x) == 1);
+      auto x2 = passThroughClassWithIntField(x);
+      assert(getRetainCount(x) == 2);
+      assert(getRetainCount(x2) == 2);
+      takeClassWithIntField(x2);
+      assert(getRetainCount(x) == 2);
+    }
+    assert(getRetainCount(x) == 1);
+    takeClassWithIntField(x);
+  }
+// CHECK-NEXT: init ClassWithIntField
+// CHECK-NEXT: ClassWithIntField: 0;
+// CHECK-NEXT: ClassWithIntField: 42;
+// CHECK-NEXT: ClassWithIntField: 42;
 // CHECK-NEXT: destroy ClassWithIntField
   return 0;
 }

test/Interop/SwiftToCxx/class/swift-class-in-cxx.swift

@@ -5,7 +5,7 @@
 // RUN: %check-interop-cxx-header-in-clang(%t/class.h)
 
 public final class ClassWithIntField {
-  let field: Int64
+  var field: Int64
 
   init() {
     field = 0
@@ -18,7 +18,9 @@ public final class ClassWithIntField {
 
 // CHECK: namespace Class {
 
-// CHECK: SWIFT_EXTERN void * _Nonnull $s5Class06returnA12WithIntFieldAA0acdE0CyF(void) SWIFT_NOEXCEPT SWIFT_CALL; // returnClassWithIntField()
+// CHECK: SWIFT_EXTERN void * _Nonnull $s5Class011passThroughA12WithIntFieldyAA0adeF0CADF(void * _Nonnull x) SWIFT_NOEXCEPT SWIFT_CALL; // passThroughClassWithIntField(_:)
+// CHECK-NEXT: SWIFT_EXTERN void * _Nonnull $s5Class06returnA12WithIntFieldAA0acdE0CyF(void) SWIFT_NOEXCEPT SWIFT_CALL; // returnClassWithIntField()
+// CHECK-NEXT: SWIFT_EXTERN void $s5Class04takeA12WithIntFieldyyAA0acdE0CF(void * _Nonnull x) SWIFT_NOEXCEPT SWIFT_CALL; // takeClassWithIntField(_:)
 
 // CHECK: namespace Class {
 
@@ -44,10 +46,15 @@ public final class ClassWithIntField {
 // CHECK-NEXT:class _impl_ClassWithIntField {
 // CHECK-NEXT:public:
 // CHECK-NEXT:static inline ClassWithIntField makeRetained(void * _Nonnull ptr) noexcept { return ClassWithIntField(ptr); }
+// CHECK-NEXT:static inline void * _Nonnull getOpaquePointer(const ClassWithIntField &object) noexcept { return object._opaquePointer; }
 // CHECK-NEXT:};
 // CHECK-EMPTY:
 // CHECK-NEXT:} // namespace _impl
 
+// CHECK: inline ClassWithIntField passThroughClassWithIntField(const ClassWithIntField& x) noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK-NEXT:  return _impl::_impl_ClassWithIntField::makeRetained(_impl::$s5Class011passThroughA12WithIntFieldyAA0adeF0CADF(_impl::_impl_ClassWithIntField::getOpaquePointer(x)));
+// CHECK-NEXT: }
+
 public final class register { }
 
 // CHECK: class register_ final {
@@ -56,6 +63,20 @@ public func returnClassWithIntField() -> ClassWithIntField {
   return ClassWithIntField()
 }
 
+
+public func passThroughClassWithIntField(_ x: ClassWithIntField) -> ClassWithIntField {
+  x.field = 42
+  return x
+}
+
+public func takeClassWithIntField(_ x: ClassWithIntField) {
+  print("ClassWithIntField: \(x.field);")
+}
+
 // CHECK: inline ClassWithIntField returnClassWithIntField() noexcept SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT:   return _impl::_impl_ClassWithIntField::makeRetained(_impl::$s5Class06returnA12WithIntFieldAA0acdE0CyF());
 // CHECK-NEXT: }
+
+// CHECK: inline void takeClassWithIntField(const ClassWithIntField& x) noexcept {
+// CHECK-NEXT:  return _impl::$s5Class04takeA12WithIntFieldyyAA0acdE0CF(_impl::_impl_ClassWithIntField::getOpaquePointer(x));
+// CHECK-NEXT: }