Merge pull request #62 from ddddxxx/fix-objc-derived-class

fix: crash when inspect class that derived from pure objc class

Author: wickwirew

Sources/Runtime/Layouts/ClassMetadataLayout.swift

@@ -22,11 +22,22 @@
 
 import Foundation
 
+// Swift class or objc class
+struct AnyClassMetadataLayout {
+    var _kind: Int // isaPointer for classes
+    var superClass: Any.Type
+    var objCRuntimeReserve: (Int, Int)
+    var rodataPointer: Int
+    
+    var isSwiftClass: Bool {
+        return (rodataPointer & classIsSwiftMask()) != 0
+    }
+}
+
 struct ClassMetadataLayout: NominalMetadataLayoutType {
     var _kind: Int // isaPointer for classes
     var superClass: Any.Type
-    var objCRuntimeReserve1: Int
-    var objCRuntimeReserve2: Int
+    var objCRuntimeReserve: (Int, Int)
     var rodataPointer: Int
     var classFlags: Int32
     var instanceAddressPoint: UInt32

Sources/Runtime/Metadata/ClassMetadata.swift

@@ -22,6 +22,23 @@
 
 import Foundation
 
+struct AnyClassMetadata {
+    
+    var pointer: UnsafeMutablePointer<AnyClassMetadataLayout>
+    
+    init(type: Any.Type) {
+        pointer = unsafeBitCast(type, to: UnsafeMutablePointer<AnyClassMetadataLayout>.self)
+    }
+    
+    func asClassMetadata() -> ClassMetadata? {
+        guard pointer.pointee.isSwiftClass else {
+            return nil
+        }
+        let ptr = pointer.raw.assumingMemoryBound(to: ClassMetadataLayout.self)
+        return ClassMetadata(pointer: ptr)
+    }
+}
+
 struct ClassMetadata: NominalMetadataType {
 
     var pointer: UnsafeMutablePointer<ClassMetadataLayout>
@@ -60,15 +77,12 @@ struct ClassMetadata: NominalMetadataType {
         fatalError("Cannot get the `genericArgumentOffset` for classes with a resilient superclass")
     }
 
-    func superClassMetadata() -> ClassMetadata? {
+    func superClassMetadata() -> AnyClassMetadata? {
         let superClass = pointer.pointee.superClass
-        // type comparison directly to NSObject.self does not work.
-        // just compare the type name instead.
-        if superClass != swiftObject() && "\(superClass)" != "NSObject" {
-            return ClassMetadata(type: superClass)
-        } else {
+        guard superClass != swiftObject() else {
             return nil
         }
+        return AnyClassMetadata(type: superClass)
     }
 
     mutating func toTypeInfo() -> TypeInfo {
@@ -77,12 +91,12 @@ struct ClassMetadata: NominalMetadataType {
         info.properties = properties()
         info.genericTypes = Array(genericArguments())
 
-        var superClass = superClassMetadata()
+        var superClass = superClassMetadata()?.asClassMetadata()
         while var sc = superClass {
             info.inheritance.append(sc.type)
             let superInfo = sc.toTypeInfo()
             info.properties.append(contentsOf: superInfo.properties)
-            superClass = sc.superClassMetadata()
+            superClass = sc.superClassMetadata()?.asClassMetadata()
         }
 
         return info

Sources/Runtime/Metadata/Metadata.swift

@@ -51,3 +51,12 @@ func swiftObject() -> Any.Type {
     let md = ClassMetadata(type: Temp.self)
     return md.pointer.pointee.superClass
 }
+
+func classIsSwiftMask() -> Int {
+    #if canImport(Darwin)
+    if #available(macOS 10.14.4, iOS 12.2, tvOS 12.2, watchOS 5.2, *) {
+        return 2
+    }
+    #endif
+    return 1
+}