Add IsSDKRelative field to ModuleInterfaceLayout

include/swift/Serialization/SerializationOptions.h

@@ -162,6 +162,7 @@ class SerializationOptions {
   bool SkipNonExportableDecls = false;
   bool ExplicitModuleBuild = false;
   bool EnableSerializationRemarks = false;
+  bool IsInterfaceSDKRelative = false;
 };
 
 } // end namespace swift

lib/Frontend/ModuleInterfaceBuilder.cpp

@@ -291,9 +291,10 @@ std::error_code ExplicitModuleInterfaceBuilder::buildSwiftModuleFromInterface(
   StringRef SDKPath = Instance.getASTContext().SearchPathOpts.getSDKPath();
 
   auto SDKRelativePath = getRelativeDepPath(InPath, SDKPath);
-  if (SDKRelativePath.has_value())
+  if (SDKRelativePath.has_value()) {
     SerializationOpts.ModuleInterface = SDKRelativePath.value();
-  else
+    SerializationOpts.IsInterfaceSDKRelative = true;
+  } else
     SerializationOpts.ModuleInterface = InPath;
 
   SerializationOpts.SDKName = Instance.getASTContext().LangOpts.SDKName;

lib/Serialization/ModuleFileSharedCore.cpp

@@ -1615,6 +1615,8 @@ ModuleFileSharedCore::ModuleFileSharedCore(
           break;
         }
         case input_block::MODULE_INTERFACE_PATH: {
+          input_block::ModuleInterfaceLayout::readRecord(
+              scratch, IsModuleInterfaceSDKRelative);
           ModuleInterfacePath = blobData;
           break;
         }
@@ -1837,10 +1839,12 @@ bool ModuleFileSharedCore::hasSourceInfo() const {
 std::string ModuleFileSharedCore::resolveModuleDefiningFilePath(const StringRef SDKPath) const {
   if (!ModuleInterfacePath.empty()) {
     std::string interfacePath = ModuleInterfacePath.str();
-    if (llvm::sys::path::is_relative(interfacePath) && !ModuleInterfacePath.starts_with(SDKPath)) {
-      SmallString<128> absoluteInterfacePath(SDKPath);
-      llvm::sys::path::append(absoluteInterfacePath, interfacePath);
-      return absoluteInterfacePath.str().str();
+    if (IsModuleInterfaceSDKRelative &&
+        !ModuleInterfacePath.starts_with(SDKPath) &&
+        llvm::sys::path::is_relative(interfacePath)) {
+      SmallString<128> resolvedPath(SDKPath);
+      llvm::sys::path::append(resolvedPath, interfacePath);
+      return resolvedPath.str().str();
     } else
       return interfacePath;
   } else

lib/Serialization/ModuleFileSharedCore.h

@@ -74,6 +74,9 @@ class ModuleFileSharedCore {
   /// Empty if this module didn't come from an interface file.
   StringRef ModuleInterfacePath;
 
+  /// true if this module interface was serialized relative to the SDK path.
+  bool IsModuleInterfaceSDKRelative = false;
+
   /// The module interface path if this module is adjacent to such an interface
   /// or it was itself compiled from an interface. Empty otherwise.
   StringRef CorrespondingInterfacePath;

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 905; // "addressable" param bit
+const uint16_t SWIFTMODULE_VERSION_MINOR = 906; // IsModuleInterfaceSDKRelative
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -1158,7 +1158,8 @@ namespace input_block {
 
   using ModuleInterfaceLayout = BCRecordLayout<
     MODULE_INTERFACE_PATH,
-    BCBlob // file path
+    BCFixed<1>, // SDK-relative?
+    BCBlob      // file path
   >;
 
 }

lib/Serialization/Serialization.cpp

@@ -1352,7 +1352,8 @@ void Serializer::writeInputBlock() {
   }
 
   if (!Options.ModuleInterface.empty())
-    ModuleInterface.emit(ScratchRecord, Options.ModuleInterface);
+    ModuleInterface.emit(ScratchRecord, Options.IsInterfaceSDKRelative,
+                         Options.ModuleInterface);
 
   SmallVector<ExternalMacroPlugin> macros;
   M->getExternalMacros(macros);

test/ModuleInterface/Inputs/relative_path/A.swiftmodule/arm64-apple-macos.swiftinterface

@@ -0,0 +1,8 @@
+// swift-interface-format-version: 1.0
+// swift-module-flags: -target arm64-apple-macosx15.0 -module-name A
+
+import B
+
+public struct AStruct {
+    var y : BStruct
+}

test/ModuleInterface/Inputs/relative_path/B.swiftmodule/arm64-apple-macos.swiftinterface

@@ -0,0 +1,9 @@
+// swift-interface-format-version: 1.0
+// swift-module-flags: -target arm64-apple-macosx15.0 -module-name B
+
+import Swift
+
+public struct BStruct {
+    var x : Int
+    public init()
+}

test/ModuleInterface/relative-interface-path.swift

@@ -0,0 +1,11 @@
+// RUN: %empty-directory(%t.relative_interface_path)
+// RUN: cp -R %S/Inputs/relative_path %t.relative_interface_path/
+// RUN: cd %t.relative_interface_path
+// RUN: mkdir out
+
+// RUN: %target-swift-frontend -target arm64-apple-macosx15.0 -compile-module-from-interface \
+// RUN:   relative_path/B.swiftmodule/arm64-apple-macos.swiftinterface -o out/B.swiftmodule
+// RUN: %target-swift-frontend -target arm64-apple-macosx15.0 -compile-module-from-interface \
+// RUN:   relative_path/A.swiftmodule/arm64-apple-macos.swiftinterface -o out/A.swiftmodule -I out
+
+// REQUIRES: OS=macosx

test/Serialization/module_defining_interface.swift

@@ -18,8 +18,8 @@
 // RUN: llvm-bcanalyzer -dump %t/inputs/Foo.swiftmodule > %t/Foo.sdk.moduledump.txt
 // RUN: cat %t/Foo.sdk.moduledump.txt | %FileCheck %s -check-prefix CHECK-SDK-FOO
 
-// CHECK-FREESTANDING-FOO: <MODULE_INTERFACE_PATH abbrevid={{[0-9]+}}/> blob data = '{{.*}}{{/|\\}}modules{{/|\\}}Foo.swiftinterface'
-// CHECK-SDK-FOO: <MODULE_INTERFACE_PATH abbrevid={{[0-9]+}}/> blob data = 'usr/lib/Foo.swiftmodule/Foo.swiftinterface'
+// CHECK-FREESTANDING-FOO: <MODULE_INTERFACE_PATH abbrevid={{[0-9]+}} op0=0/> blob data = '{{.*}}{{/|\\}}modules{{/|\\}}Foo.swiftinterface'
+// CHECK-SDK-FOO: <MODULE_INTERFACE_PATH abbrevid={{[0-9]+}} op0=1/> blob data = 'usr/lib/Foo.swiftmodule/Foo.swiftinterface'
 
 //--- modules/Foo.swiftinterface
 // swift-interface-format-version: 1.0