[interop][SwiftToCxx] support std::string -> Swift::String conversion in C++

Author: hyp

lib/PrintAsClang/ModuleContentsWriter.cpp

@@ -776,6 +776,10 @@ EmittedClangHeaderDependencyInfo swift::printModuleContentsAsCxx(
   writer.write();
   info.dependsOnStandardLibrary = writer.isStdlibRequired();
   if (M.isStdlibModule()) {
+    // Embed additional STL includes.
+    os << "#ifndef SWIFT_CXX_INTEROP_HIDE_STL_OVERLAY\n";
+    os << "#include <string>\n";
+    os << "#endif\n";
     // Embed an overlay for the standard library.
     ClangSyntaxPrinter(moduleOS).printIncludeForShimHeader(
         "_SwiftStdlibCxxOverlay.h");

lib/PrintAsClang/PrintClangValueType.cpp

@@ -95,6 +95,7 @@ void ClangValueTypePrinter::forwardDeclType(raw_ostream &os,
 }
 
 static void addCppExtensionsToStdlibType(const NominalTypeDecl *typeDecl,
+                                         raw_ostream &os,
                                          ClangSyntaxPrinter &printer,
                                          raw_ostream &cPrologueOS) {
   if (typeDecl == typeDecl->getASTContext().getStringDecl()) {
@@ -135,6 +136,9 @@ static void addCppExtensionsToStdlibType(const NominalTypeDecl *typeDecl,
                    "$sSS10FoundationE36_"
                    "unconditionallyBridgeFromObjectiveCySSSo8NSStringCSgFZ("
                    "void * _Nullable) SWIFT_NOEXCEPT SWIFT_CALL;\n";
+    cPrologueOS << "SWIFT_EXTERN swift_interop_stub_Swift_String "
+                   "$sSS7cStringSSSPys4Int8VG_tcfC("
+                   "const char * _Nonnull) SWIFT_NOEXCEPT SWIFT_CALL;\n";
     printer.printObjCBlock([](raw_ostream &os) {
       os << "  ";
       ClangSyntaxPrinter(os).printInlineForThunk();
@@ -155,6 +159,14 @@ static void addCppExtensionsToStdlibType(const NominalTypeDecl *typeDecl,
       os << "    return result;\n";
       os << "  }\n";
     });
+    os << "#ifndef SWIFT_CXX_INTEROP_HIDE_STL_OVERLAY\n";
+    ClangSyntaxPrinter(os).printInlineForThunk();
+    os << "String(const std::string &str) noexcept {\n";
+    os << "    auto res = "
+          "_impl::$sSS7cStringSSSPys4Int8VG_tcfC(str.c_str());\n";
+    os << "    memcpy(_getOpaquePointer(), &res, sizeof(res));\n";
+    os << "}\n";
+    os << "#endif\n";
   } else if (typeDecl == typeDecl->getASTContext().getOptionalDecl()) {
     // Add additional methods for the `Optional` declaration.
     printer.printDefine("SWIFT_CXX_INTEROP_OPTIONAL_MIXIN");
@@ -295,7 +307,7 @@ void ClangValueTypePrinter::printValueTypeDecl(
 
   bodyPrinter();
   if (typeDecl->isStdlibDecl())
-    addCppExtensionsToStdlibType(typeDecl, printer, cPrologueOS);
+    addCppExtensionsToStdlibType(typeDecl, os, printer, cPrologueOS);
 
   os << "private:\n";
 

test/Interop/SwiftToCxx/functions/swift-functions-errors.swift

@@ -2,7 +2,7 @@
 // RUN: %target-swift-frontend %s -typecheck -module-name Functions -enable-experimental-cxx-interop -emit-clang-header-path %t/functions.h
 // RUN: %FileCheck %s < %t/functions.h
 
-// RUN: %check-interop-cxx-header-in-clang(%t/functions.h -Wno-shadow -Wno-unused-function)
+// RUN: %check-interop-cxx-header-in-clang(%t/functions.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY  -Wno-shadow -Wno-unused-function)
 
 // CHECK-LABEL: namespace Functions __attribute__((swift_private)) {
 

test/Interop/SwiftToCxx/stdlib/stdlib-dep-inline-in-cxx.swift

@@ -7,7 +7,7 @@
 
 // RUN: cat %t/stdlib.h %t/stdlib2.h > %t/two_includes.h
 
-// RUN: %check-interop-cxx-header-in-clang(%t/two_includes.h -Wno-unused-private-field -Wno-unused-function -Wno-shadow)
+// RUN: %check-interop-cxx-header-in-clang(-DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY %t/two_includes.h -Wno-unused-private-field -Wno-unused-function -Wno-shadow)
 
 @_expose(Cxx)
 public func test() -> String {

test/Interop/SwiftToCxx/stdlib/string/string-conversions.cpp

@@ -0,0 +1,41 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-frontend -typecheck %t/print-string.swift -typecheck -module-name Stringer -enable-experimental-cxx-interop -emit-clang-header-path %t/Stringer.h
+
+// RUN: %target-interop-build-clangxx -std=gnu++20 -c %t/string-conversions.cpp -I %t -o %t/swift-stdlib-execution.o
+// RUN: %target-build-swift %t/print-string.swift -o %t/swift-stdlib-execution -Xlinker %t/swift-stdlib-execution.o -module-name Stringer -Xfrontend -entry-point-function-name -Xfrontend swiftMain %target-cxx-lib
+// RUN: %target-codesign %t/swift-stdlib-execution
+// RUN: %target-run %t/swift-stdlib-execution | %FileCheck %s
+
+// REQUIRES: executable_test
+
+//--- print-string.swift
+
+@_expose(Cxx)
+public func printString(_ s: String) {
+    print("'''\(s)'''")
+}
+
+//--- string-conversions.cpp
+
+#include <cassert>
+#include "Stringer.h"
+
+int main() {
+  using namespace Swift;
+  using namespace Stringer;
+
+  {
+    auto s = String("hello world");
+    printString(s);
+  }
+// CHECK: '''hello world'''
+
+  {
+    std::string str = "test std::string";
+    printString(str);
+  }
+// CHECK-NEXT: '''test std::string'''
+  return 0;
+}

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

@@ -2,7 +2,7 @@
 // RUN: %target-swift-frontend -parse-as-library %platform-module-dir/Swift.swiftmodule/%module-target-triple.swiftinterface -enable-library-evolution -disable-objc-attr-requires-foundation-module -typecheck -module-name Swift -parse-stdlib -enable-experimental-cxx-interop -emit-clang-header-path %t/Swift.h  -experimental-skip-all-function-bodies
 // RUN: %FileCheck %s < %t/Swift.h
 
-// RUN: %check-interop-cxx-header-in-clang(%t/Swift.h -Wno-unused-private-field -Wno-unused-function -Wno-shadow)
+// RUN: %check-interop-cxx-header-in-clang(%t/Swift.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY -Wno-unused-private-field -Wno-unused-function -Wno-shadow)
 
 // FIXME: remove need for -Wno-shadow
 
@@ -87,6 +87,12 @@
 // CHECK-NEXT:  }
 // CHECK-EMPTY:
 // CHECK-NEXT:  #endif
+// CHECK-NEXT: #ifndef SWIFT_CXX_INTEROP_HIDE_STL_OVERLAY
+// CHECK-NEXT: inline __attribute__((always_inline)) String(const std::string &str) noexcept {
+// CHECK-NEXT:      auto res = _impl::$sSS7cStringSSSPys4Int8VG_tcfC(str.c_str());
+// CHECK-NEXT:      memcpy(_getOpaquePointer(), &res, sizeof(res));
+// CHECK-NEXT: }
+// CHECK-NEXT: #endif
 // CHECK-NEXT: private:
 
 // CHECK: #if __has_include(<../../../swift/swiftToCxx/_SwiftStdlibCxxOverlay.h>)

test/Interop/SwiftToCxxToSwift/hide-swift-module-namespace-in-swift.swift

@@ -8,7 +8,7 @@
 
 // RUN: %target-swift-frontend -typecheck %t/swiftMod.swift -typecheck -module-name SwiftMod -emit-clang-header-path %t/swiftMod2.h -I %t -enable-experimental-cxx-interop
 
-// RUN: %check-interop-cxx-header-in-clang(%t/swiftMod2.h -Wno-error)
+// RUN: %check-interop-cxx-header-in-clang(%t/swiftMod2.h -DSWIFT_CXX_INTEROP_HIDE_STL_OVERLAY  -Wno-error)
 
 // XFAIL: OS=linux-android, OS=linux-androideabi