8361481: Flexible Constructor Bodies generates a compilation error when compiling a user supplied java.lang.Object class

Reviewed-by: vromero, liach, jlahoda

Author: mcimadamore

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Attr.java

@@ -1236,8 +1236,8 @@ public void visitMethodDef(JCMethodDecl tree) {
                 annotate.queueScanTreeAndTypeAnnotate(tree.body, localEnv, m, null);
                 annotate.flush();
 
-                // Start of constructor prologue
-                localEnv.info.ctorPrologue = isConstructor;
+                // Start of constructor prologue (if not in java.lang.Object constructor)
+                localEnv.info.ctorPrologue = isConstructor && owner.type != syms.objectType;
 
                 // Attribute method body.
                 attribStat(tree.body, localEnv);

test/langtools/tools/javac/ObjectEarlyContext/T8361481.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+
+
+/*
+ * @test
+ * @bug 8361481
+ * @modules jdk.compiler
+ * @summary Flexible Constructor Bodies generates a compilation error when compiling a user supplied java.lang.Object class
+ */
+
+import java.io.*;
+import java.util.*;
+
+public class T8361481 {
+    static String testSrc = System.getProperty("test.src", ".");
+
+    public static void main(String... args) throws Exception {
+        new T8361481().run();
+    }
+
+    public void run() throws Exception {
+        // compile modified Object.java, using patch-module to avoid errors
+        File x = new File(testSrc, "x");
+        String[] jcArgs = { "-d", ".", "--patch-module", "java.base=" + x.getAbsolutePath(),
+                new File(new File(new File(x, "java"), "lang"), "Object.java").getPath()};
+        compile(jcArgs);
+    }
+
+    void compile(String... args) {
+        int rc = com.sun.tools.javac.Main.compile(args);
+        if (rc != 0)
+            throw new Error("javac failed: " + Arrays.asList(args) + ": " + rc);
+    }
+}
+

test/langtools/tools/javac/ObjectEarlyContext/x/java/lang/Object.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.lang;
+
+public class Object {
+    public Object() {
+        foo(); // valid, not in early constructor context
+    }
+
+    void foo() { }
+}