[interop][SwiftToCxx] Annotate emitted declarations with Clang's external_source_symbol attribute

Each emitted declaration is annotated with the external_source_symbol with its own USR, to allow Clang's indexer to recognize this declaration as a Swift declaration with a specific USR

Author: hyp

lib/PrintAsClang/ClangSyntaxPrinter.cpp

@@ -12,9 +12,11 @@
 
 #include "ClangSyntaxPrinter.h"
 #include "swift/ABI/MetadataValues.h"
+#include "swift/AST/ASTContext.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/Module.h"
 #include "swift/AST/SwiftNameTranslation.h"
+#include "swift/AST/TypeCheckRequests.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/NestedNameSpecifier.h"
@@ -140,18 +142,21 @@ void ClangSyntaxPrinter::printModuleNamespaceStart(
   os << "namespace ";
   printBaseName(&moduleContext);
   os << " __attribute__((swift_private))";
+  printSymbolUSRAttribute(&moduleContext);
   os << " {\n";
 }
 
 /// Print a C++ namespace declaration with the give name and body.
 void ClangSyntaxPrinter::printNamespace(
     llvm::function_ref<void(raw_ostream &OS)> namePrinter,
     llvm::function_ref<void(raw_ostream &OS)> bodyPrinter,
-    NamespaceTrivia trivia) const {
+    NamespaceTrivia trivia, const ModuleDecl *moduleContext) const {
   os << "namespace ";
   namePrinter(os);
   if (trivia == NamespaceTrivia::AttributeSwiftPrivate)
     os << " __attribute__((swift_private))";
+  if (moduleContext)
+    printSymbolUSRAttribute(moduleContext);
   os << " {\n\n";
   bodyPrinter(os);
   os << "\n} // namespace ";
@@ -405,3 +410,17 @@ void ClangSyntaxPrinter::printIgnoredCxx17ExtensionDiagnosticBlock(
     llvm::function_ref<void()> bodyPrinter) {
   printIgnoredDiagnosticBlock("c++17-extensions", bodyPrinter);
 }
+
+void ClangSyntaxPrinter::printSymbolUSRAttribute(const ValueDecl *D) const {
+  if (isa<ModuleDecl>(D)) {
+    os << " SWIFT_SYMBOL_MODULE(\"";
+    printBaseName(D);
+    os << "\")";
+    return;
+  }
+  auto result = evaluateOrDefault(D->getASTContext().evaluator,
+                                  USRGenerationRequest{D}, std::string());
+  if (result.empty())
+    return;
+  os << " SWIFT_SYMBOL(\"" << result << "\")";
+}

lib/PrintAsClang/ClangSyntaxPrinter.h

@@ -125,7 +125,8 @@ class ClangSyntaxPrinter {
   /// Print a C++ namespace declaration with the give name and body.
   void printNamespace(llvm::function_ref<void(raw_ostream &OS)> namePrinter,
                       llvm::function_ref<void(raw_ostream &OS)> bodyPrinter,
-                      NamespaceTrivia trivia = NamespaceTrivia::None) const;
+                      NamespaceTrivia trivia = NamespaceTrivia::None,
+                      const ModuleDecl *moduleContext = nullptr) const;
 
   void printNamespace(StringRef name,
                       llvm::function_ref<void(raw_ostream &OS)> bodyPrinter,
@@ -220,6 +221,10 @@ class ClangSyntaxPrinter {
   void printIgnoredCxx17ExtensionDiagnosticBlock(
       llvm::function_ref<void()> bodyPrinter);
 
+  /// Print the macro that applies Clang's `external_source_symbol` attribute
+  /// on the generated declaration.
+  void printSymbolUSRAttribute(const ValueDecl *D) const;
+
 protected:
   raw_ostream &os;
 };

lib/PrintAsClang/ModuleContentsWriter.cpp

@@ -788,6 +788,14 @@ EmittedClangHeaderDependencyInfo swift::printModuleContentsAsCxx(
   llvm::raw_string_ostream prologueOS{modulePrologueBuf};
   EmittedClangHeaderDependencyInfo info;
 
+  // Define the `SWIFT_SYMBOL` macro.
+  os << "#ifdef SWIFT_SYMBOL\n";
+  os << "#undef SWIFT_SYMBOL\n";
+  os << "#endif\n";
+  os << "#define SWIFT_SYMBOL(usrValue) SWIFT_SYMBOL_MODULE_USR(\"";
+  ClangSyntaxPrinter(os).printBaseName(&M);
+  os << "\", usrValue)\n";
+
   // FIXME: Use getRequiredAccess once @expose is supported.
   ModuleWriter writer(moduleOS, prologueOS, info.imports, M, interopContext,
                       AccessLevel::Public, requiresExposedAttribute,
@@ -824,6 +832,7 @@ EmittedClangHeaderDependencyInfo swift::printModuleContentsAsCxx(
     os << "namespace ";
     M.ValueDecl::getName().print(os);
     os << " __attribute__((swift_private))";
+    ClangSyntaxPrinter(os).printSymbolUSRAttribute(&M);
     os << " {\n";
     os << "namespace " << cxx_synthesis::getCxxImplNamespaceName() << " {\n";
     os << "extern \"C\" {\n";
@@ -842,10 +851,11 @@ EmittedClangHeaderDependencyInfo swift::printModuleContentsAsCxx(
   ClangSyntaxPrinter(os).printNamespace(
       [&](raw_ostream &os) { M.ValueDecl::getName().print(os); },
       [&](raw_ostream &os) { os << moduleOS.str(); },
-      ClangSyntaxPrinter::NamespaceTrivia::AttributeSwiftPrivate);
+      ClangSyntaxPrinter::NamespaceTrivia::AttributeSwiftPrivate, &M);
 
   if (M.isStdlibModule()) {
     os << "#pragma clang diagnostic pop\n";
   }
+  os << "#undef SWIFT_SYMBOL\n";
   return info;
 }

lib/PrintAsClang/PrintClangClassType.cpp

@@ -58,7 +58,9 @@ void ClangClassTypePrinter::printClassTypeDecl(
     baseClassQualifiedName = "swift::_impl::RefCountedClass";
   }
 
-  os << "class ";
+  os << "class";
+  ClangSyntaxPrinter(os).printSymbolUSRAttribute(typeDecl);
+  os << ' ';
   printer.printBaseName(typeDecl);
   if (typeDecl->isFinal())
     os << " final";

lib/PrintAsClang/PrintClangFunction.cpp

@@ -905,6 +905,9 @@ ClangRepresentation DeclAndTypeClangFunctionPrinter::printFunctionSignature(
     os << " const";
   if (modifiers.isNoexcept)
     os << " noexcept";
+  if (modifiers.hasSymbolUSR)
+    ClangSyntaxPrinter(os).printSymbolUSRAttribute(
+        modifiers.symbolUSROverride ? modifiers.symbolUSROverride : FD);
   return resultingRepresentation;
 }
 
@@ -1311,6 +1314,7 @@ void DeclAndTypeClangFunctionPrinter::printCxxMethod(
       isa<FuncDecl>(FD) ? cast<FuncDecl>(FD)->isMutating() : false;
   modifiers.isConst =
       !isa<ClassDecl>(typeDeclContext) && !isMutating && !isConstructor;
+  modifiers.hasSymbolUSR = !isDefinition;
   auto result = printFunctionSignature(
       FD, signature,
       isConstructor ? getConstructorName(FD)
@@ -1375,6 +1379,8 @@ void DeclAndTypeClangFunctionPrinter::printCxxPropertyAccessorMethod(
   modifiers.isInline = true;
   modifiers.isConst =
       !isStatic && accessor->isGetter() && !isa<ClassDecl>(typeDeclContext);
+  modifiers.hasSymbolUSR = !isDefinition;
+  modifiers.symbolUSROverride = accessor->getStorage();
   auto result = printFunctionSignature(
       accessor, signature, remapPropertyName(accessor, resultTy), resultTy,
       FunctionSignatureKind::CxxInlineThunk, modifiers);

lib/PrintAsClang/PrintClangFunction.h

@@ -87,6 +87,10 @@ class DeclAndTypeClangFunctionPrinter {
     bool isInline = false;
     bool isConst = false;
     bool isNoexcept = false;
+    bool hasSymbolUSR = true;
+    /// Specific declaration that should be used to emit the symbol's
+    /// USR instead of the original function declaration.
+    const ValueDecl *symbolUSROverride = nullptr;
 
     FunctionSignatureModifiers() {}
   };

lib/PrintAsClang/PrintClangValueType.cpp

@@ -88,7 +88,9 @@ void ClangValueTypePrinter::forwardDeclType(raw_ostream &os,
         typeDecl->getGenericSignature().getCanonicalSignature();
     ClangSyntaxPrinter(os).printGenericSignature(genericSignature);
   }
-  os << "class ";
+  os << "class";
+  ClangSyntaxPrinter(os).printSymbolUSRAttribute(typeDecl);
+  os << ' ';
   ClangSyntaxPrinter(os).printBaseName(typeDecl);
   os << ";\n";
   printTypePrecedingGenericTraits(os, typeDecl, typeDecl->getModuleContext());
@@ -259,7 +261,9 @@ void ClangValueTypePrinter::printValueTypeDecl(
 
   // Print out the C++ class itself.
   printGenericSignature(os);
-  os << "class ";
+  os << "class";
+  ClangSyntaxPrinter(os).printSymbolUSRAttribute(typeDecl);
+  os << ' ';
   ClangSyntaxPrinter(os).printBaseName(typeDecl);
   os << " final {\n";
   os << "public:\n";

lib/PrintAsClang/_SwiftCxxInteroperability.h

@@ -31,6 +31,29 @@
 // FIXME: Use always_inline, artificial.
 #define SWIFT_INLINE_THUNK inline
 
+/// The `SWIFT_SYMBOL_MODULE` and `SWIFT_SYMBOL_MODULE_USR` macros apply
+/// `external_source_symbol` Clang attributes to C++ declarations that represent
+/// Swift declarations. This allows Clang to index them as external
+/// declarations, using the specified Swift USR values.
+#if __has_attribute(external_source_symbol)
+#define SWIFT_SYMBOL_MODULE(moduleValue)                                       \
+  __attribute__((external_source_symbol(                                       \
+      language = "Swift", defined_in = moduleValue, generated_declaration)))
+#if __has_attribute(external_source_symbol_with_usr)
+#define SWIFT_SYMBOL_MODULE_USR(moduleValue, usrValue)                         \
+  __attribute__((                                                              \
+      external_source_symbol(language = "Swift", defined_in = moduleValue,     \
+                             generated_declaration, USR = usrValue)))
+#else
+#define SWIFT_SYMBOL_MODULE_USR(moduleValue, usrValue)                         \
+  __attribute__((external_source_symbol(                                       \
+      language = "Swift", defined_in = moduleValue, generated_declaration)))
+#endif
+#else
+#define SWIFT_SYMBOL_MODULE_USR(moduleValue, usrValue)
+#define SWIFT_SYMBOL_MODULE(moduleValue)
+#endif
+
 namespace swift {
 namespace _impl {
 

test/Interop/CxxToSwiftToCxx/bridge-cxx-struct-back-to-cxx.swift

@@ -156,11 +156,11 @@ public func takeTrivialInout(_ x: inout Trivial) {
 // CHECK: SWIFT_EXTERN void $s8UseCxxTy13retNonTrivialSo2nsO02__b18TemplateInstN2ns18efH4IiEEVyF(SWIFT_INDIRECT_RESULT void * _Nonnull) SWIFT_NOEXCEPT SWIFT_CALL; // retNonTrivial()
 // CHECK: SWIFT_EXTERN struct swift_interop_returnStub_UseCxxTy_uint32_t_0_4 $s8UseCxxTy10retTrivialSo0E0VyF(void) SWIFT_NOEXCEPT SWIFT_CALL; // retTrivial()
 
-// CHECK: ns::Immortal *_Nonnull retImmortal() noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK: ns::Immortal *_Nonnull retImmortal() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: return _impl::$s8UseCxxTy11retImmortalSo2nsO0E0VyF();
 // CHECK-NEXT: }
 
-// CHECK:  ns::ImmortalTemplate<int> *_Nonnull retImmortalTemplate() noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK:  ns::ImmortalTemplate<int> *_Nonnull retImmortalTemplate() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: return _impl::$s8UseCxxTy19retImmortalTemplateSo2nsO02__bf10InstN2ns16eF4IiEEVyF();
 // CHECK-NEXT: }
 
@@ -192,9 +192,9 @@ public func takeTrivialInout(_ x: inout Trivial) {
 // CHECK-NEXT: #pragma clang diagnostic pop
 // CHECK-NEXT: } // namespace swift
 // CHECK-EMPTY:
-// CHECK-NEXT: namespace UseCxxTy __attribute__((swift_private)) {
+// CHECK-NEXT: namespace UseCxxTy __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("UseCxxTy") {
 
-// CHECK: inline ns::NonTrivialTemplate<int> retNonTrivial() noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK: inline ns::NonTrivialTemplate<int> retNonTrivial() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: alignas(alignof(ns::NonTrivialTemplate<int>)) char storage[sizeof(ns::NonTrivialTemplate<int>)];
 // CHECK-NEXT: auto * _Nonnull storageObjectPtr = reinterpret_cast<ns::NonTrivialTemplate<int> *>(storage);
 // CHECK-NEXT: _impl::$s8UseCxxTy13retNonTrivialSo2nsO02__b18TemplateInstN2ns18efH4IiEEVyF(storage);
@@ -231,9 +231,9 @@ public func takeTrivialInout(_ x: inout Trivial) {
 // CHECK-NEXT: #pragma clang diagnostic pop
 // CHECK-NEXT: } // namespace swift
 // CHECK-EMPTY:
-// CHECK-NEXT: namespace UseCxxTy __attribute__((swift_private)) {
+// CHECK-NEXT: namespace UseCxxTy __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("UseCxxTy") {
 // CHECK-EMPTY:
-// CHECK-NEXT: inline ns::NonTrivialTemplate<ns::TrivialinNS> retNonTrivial2() noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK-NEXT: inline ns::NonTrivialTemplate<ns::TrivialinNS> retNonTrivial2() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: alignas(alignof(ns::NonTrivialTemplate<ns::TrivialinNS>)) char storage[sizeof(ns::NonTrivialTemplate<ns::TrivialinNS>)];
 // CHECK-NEXT: auto * _Nonnull storageObjectPtr = reinterpret_cast<ns::NonTrivialTemplate<ns::TrivialinNS> *>(storage);
 // CHECK-NEXT: _impl::$s8UseCxxTy14retNonTrivial2So2nsO02__b18TemplateInstN2ns18e7TrivialH20INS_11TrivialinNSEEEVyF(storage);
@@ -242,7 +242,7 @@ public func takeTrivialInout(_ x: inout Trivial) {
 // CHECK-NEXT: return result;
 // CHECK-NEXT: }
 
-// CHECK: inline ns::NonTrivialImplicitMove retNonTrivialImplicitMove() noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK: inline ns::NonTrivialImplicitMove retNonTrivialImplicitMove() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: alignas(alignof(ns::NonTrivialImplicitMove)) char storage[sizeof(ns::NonTrivialImplicitMove)];
 // CHECK-NEXT: auto * _Nonnull storageObjectPtr = reinterpret_cast<ns::NonTrivialImplicitMove *>(storage);
 // CHECK-NEXT: _impl::$s8UseCxxTy25retNonTrivialImplicitMoveSo2nsO0efgH0VyF(storage);
@@ -251,31 +251,31 @@ public func takeTrivialInout(_ x: inout Trivial) {
 // CHECK-NEXT: return result;
 // CHECK-NEXT: }
 
-// CHECK: ns::NonTrivialTemplate<ns::TrivialinNS> retNonTrivialTypeAlias() noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK: ns::NonTrivialTemplate<ns::TrivialinNS> retNonTrivialTypeAlias() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 
-// CHECK: inline Trivial retTrivial() noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK: inline Trivial retTrivial() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: alignas(alignof(Trivial)) char storage[sizeof(Trivial)];
 // CHECK-NEXT: auto * _Nonnull storageObjectPtr = reinterpret_cast<Trivial *>(storage);
 // CHECK-NEXT: _impl::swift_interop_returnDirect_UseCxxTy_uint32_t_0_4(storage, _impl::$s8UseCxxTy10retTrivialSo0E0VyF());
 // CHECK-NEXT: return *storageObjectPtr;
 // CHECK-NEXT: }
 
-// CHECK: void takeImmortal(ns::Immortal *_Nonnull x) noexcept {
+// CHECK: void takeImmortal(ns::Immortal *_Nonnull x) noexcept SWIFT_SYMBOL({{.*}}) {
 // CHECK-NEXT: return _impl::$s8UseCxxTy12takeImmortalyySo2nsO0E0VF(x);
 // CHECK-NEXT: }
 
-// CHECK: void takeImmortalTemplate(ns::ImmortalTemplate<int> *_Nonnull x) noexcept {
+// CHECK: void takeImmortalTemplate(ns::ImmortalTemplate<int> *_Nonnull x) noexcept SWIFT_SYMBOL({{.*}}) {
 // CHECK-NEXT:   return _impl::$s8UseCxxTy20takeImmortalTemplateyySo2nsO02__bf10InstN2ns16eF4IiEEVF(x);
 // CHECK-NEXT: }
 
-// CHECK: inline void takeNonTrivial2(const ns::NonTrivialTemplate<ns::TrivialinNS>& x) noexcept {
+// CHECK: inline void takeNonTrivial2(const ns::NonTrivialTemplate<ns::TrivialinNS>& x) noexcept SWIFT_SYMBOL({{.*}}) {
 // CHECK-NEXT:   return _impl::$s8UseCxxTy15takeNonTrivial2yySo2nsO02__b18TemplateInstN2ns18e7TrivialH20INS_11TrivialinNSEEEVF(swift::_impl::getOpaquePointer(x));
 // CHECK-NEXT: }
 
-// CHECK: inline void takeTrivial(const Trivial& x) noexcept {
+// CHECK: inline void takeTrivial(const Trivial& x) noexcept SWIFT_SYMBOL({{.*}}) {
 // CHECK-NEXT:   return _impl::$s8UseCxxTy11takeTrivialyySo0E0VF(_impl::swift_interop_passDirect_UseCxxTy_uint32_t_0_4(reinterpret_cast<const char *>(swift::_impl::getOpaquePointer(x))));
 // CHECK-NEXT: }
 
-// CHECK: inline void takeTrivialInout(Trivial& x) noexcept {
+// CHECK: inline void takeTrivialInout(Trivial& x) noexcept SWIFT_SYMBOL({{.*}}) {
 // CHECK-NEXT:   return _impl::$s8UseCxxTy16takeTrivialInoutyySo0E0VzF(swift::_impl::getOpaquePointer(x));
 // CHECK-NEXT: }

test/Interop/ObjCToSwiftToObjCxx/bridge-objc-types-back-to-objcxx.swift

@@ -59,17 +59,17 @@ public func retObjClassNullable() -> ObjCKlass? {
 // CHECK-NEXT: void $s9UseObjCTy04takeB11CClassInoutyySo0B6CKlassCzF(ObjCKlass *_Nonnull __strong * _Nonnull x) SWIFT_NOEXCEPT SWIFT_CALL;
 // CHECK-NEXT: void $s9UseObjCTy04takeB14CClassNullableyySo0B6CKlassCSgF(ObjCKlass *_Nullable x) SWIFT_NOEXCEPT SWIFT_CALL;
 
-// CHECK: inline ObjCKlass *_Nonnull retObjClass() noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK: inline ObjCKlass *_Nonnull retObjClass() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: return (__bridge_transfer ObjCKlass *)(__bridge void *)_impl::$s9UseObjCTy03retB5ClassSo0B6CKlassCyF();
 
-// CHECK: inline ObjCKlass *_Nullable retObjClassNullable() noexcept SWIFT_WARN_UNUSED_RESULT {
+// CHECK: inline ObjCKlass *_Nullable retObjClassNullable() noexcept SWIFT_SYMBOL({{.*}}) SWIFT_WARN_UNUSED_RESULT {
 // CHECK-NEXT: return (__bridge_transfer ObjCKlass *)(__bridge void *)_impl::$s9UseObjCTy03retB13ClassNullableSo0B6CKlassCSgyF();
 
-// CHECK: void takeObjCClass(ObjCKlass *_Nonnull x) noexcept {
+// CHECK: void takeObjCClass(ObjCKlass *_Nonnull x) noexcept SWIFT_SYMBOL({{.*}}) {
 // CHECK-NEXT: return _impl::$s9UseObjCTy04takeB6CClassyySo0B6CKlassCF(x);
 
-// CHECK: inline void takeObjCClassInout(ObjCKlass *_Nonnull __strong & x) noexcept {
+// CHECK: inline void takeObjCClassInout(ObjCKlass *_Nonnull __strong & x) noexcept SWIFT_SYMBOL({{.*}}) {
 // CHECK-NEXT: return _impl::$s9UseObjCTy04takeB11CClassInoutyySo0B6CKlassCzF(&x);
 
-// CHECK: inline void takeObjCClassNullable(ObjCKlass *_Nullable x) noexcept {
+// CHECK: inline void takeObjCClassNullable(ObjCKlass *_Nullable x) noexcept SWIFT_SYMBOL({{.*}}) {
 // CHECK-NEXT: return _impl::$s9UseObjCTy04takeB14CClassNullableyySo0B6CKlassCSgF(x);

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

@@ -30,13 +30,13 @@ public final actor ActorWithField {
   }
 }
 
-// CHECK: namespace Actor __attribute__((swift_private)) {
+// CHECK: namespace Actor __attribute__((swift_private)) SWIFT_SYMBOL_MODULE("Actor") {
 // CHECK: SWIFT_EXTERN void * _Nonnull $s5Actor0A9WithFieldCACycfC(SWIFT_CONTEXT void * _Nonnull _self) SWIFT_NOEXCEPT SWIFT_CALL; // init()
 // CHECK: SWIFT_EXTERN void $s5Actor0A9WithFieldC6methodyyF(SWIFT_CONTEXT void * _Nonnull _self) SWIFT_NOEXCEPT SWIFT_CALL; // method()
 
-// CHECK: class ActorWithField final : public swift::_impl::RefCountedClass {
-// CHECK:   static inline ActorWithField init();
-// CHECK:   inline void method();
+// CHECK: class SWIFT_SYMBOL("s:5Actor0A9WithFieldC") ActorWithField final : public swift::_impl::RefCountedClass {
+// CHECK:   static inline ActorWithField init() SWIFT_SYMBOL("s:5Actor0A9WithFieldCACycfc");
+// CHECK:   inline void method() SWIFT_SYMBOL("s:5Actor0A9WithFieldC6methodyyF");
 
 @_expose(Cxx)
 public func takeActorWithIntField(_ x: ActorWithField) {