8336777: BufferedMethodBuilder not initialized with static flag

src/java.base/share/classes/jdk/internal/classfile/impl/BufferedMethodBuilder.java

@@ -25,6 +25,7 @@
 package jdk.internal.classfile.impl;
 
 import java.lang.constant.MethodTypeDesc;
+import java.lang.reflect.AccessFlag;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
@@ -44,7 +45,7 @@
 import java.lang.classfile.constantpool.Utf8Entry;
 
 public final class BufferedMethodBuilder
-        implements TerminalMethodBuilder, MethodInfo {
+        implements TerminalMethodBuilder {
     private final List<MethodElement> elements;
     private final SplitConstantPool constantPool;
     private final ClassFileImpl context;
@@ -59,23 +60,32 @@ public BufferedMethodBuilder(SplitConstantPool constantPool,
                                  ClassFileImpl context,
                                  Utf8Entry nameInfo,
                                  Utf8Entry typeInfo,
+                                 int flags,
                                  MethodModel original) {
         this.elements = new ArrayList<>();
         this.constantPool = constantPool;
         this.context = context;
         this.name = nameInfo;
         this.desc = typeInfo;
-        this.flags = AccessFlags.ofMethod();
+        this.flags = AccessFlags.ofMethod(flags);
         this.original = original;
     }
 
     @Override
     public MethodBuilder with(MethodElement element) {
         elements.add(element);
-        if (element instanceof AccessFlags f) this.flags = f;
+        if (element instanceof AccessFlags f) this.flags = checkFlags(f);
         return this;
     }
 
+    private AccessFlags checkFlags(AccessFlags updated) {
+        boolean wasStatic = updated.has(AccessFlag.STATIC);
+        boolean isStatic = flags.has(AccessFlag.STATIC);
+        if (wasStatic != isStatic)
+            throw new IllegalArgumentException("Cannot change ACC_STATIC flag of method");
+        return updated;
+    }
+
     @Override
     public ConstantPoolBuilder constantPool() {
         return constantPool;

src/java.base/share/classes/jdk/internal/classfile/impl/ChainedClassBuilder.java

@@ -79,7 +79,7 @@ public ClassBuilder transformField(FieldModel field, FieldTransform transform) {
     public ClassBuilder withMethod(Utf8Entry name, Utf8Entry descriptor, int flags,
                                    Consumer<? super MethodBuilder> handler) {
         consumer.accept(new BufferedMethodBuilder(terminal.constantPool, terminal.context,
-                                                         name, descriptor, null)
+                                                         name, descriptor, flags, null)
                                        .run(handler)
                                        .toModel());
         return this;
@@ -88,7 +88,7 @@ public ClassBuilder withMethod(Utf8Entry name, Utf8Entry descriptor, int flags,
     @Override
     public ClassBuilder transformMethod(MethodModel method, MethodTransform transform) {
         BufferedMethodBuilder builder = new BufferedMethodBuilder(terminal.constantPool, terminal.context,
-                                                                  method.methodName(), method.methodType(), method);
+                                                                  method.methodName(), method.methodType(), method.flags().flagsMask(), method);
         builder.transform(method, transform);
         consumer.accept(builder.toModel());
         return this;

src/java.base/share/classes/jdk/internal/classfile/impl/DirectMethodBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2024, 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
@@ -42,7 +42,7 @@
 
 public final class DirectMethodBuilder
         extends AbstractDirectBuilder<MethodModel>
-        implements TerminalMethodBuilder, WritableElement<MethodModel>, MethodInfo {
+        implements TerminalMethodBuilder, WritableElement<MethodModel> {
 
     final Utf8Entry name;
     final Utf8Entry desc;

src/java.base/share/classes/jdk/internal/classfile/impl/MethodInfo.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2024, 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
@@ -29,7 +29,8 @@
 
 import static java.lang.classfile.ClassFile.ACC_STATIC;
 
-public interface MethodInfo {
+public sealed interface MethodInfo
+        permits MethodImpl, TerminalMethodBuilder, BufferedMethodBuilder.Model {
     Utf8Entry methodName();
     Utf8Entry methodType();
     MethodTypeDesc methodTypeSymbol();

src/java.base/share/classes/jdk/internal/classfile/impl/TerminalMethodBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2024, 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
@@ -28,7 +28,7 @@
 import java.lang.classfile.MethodBuilder;
 
 public sealed interface TerminalMethodBuilder
-        extends MethodBuilder
+        extends MethodBuilder, MethodInfo
         permits BufferedMethodBuilder, DirectMethodBuilder {
     BufferedCodeBuilder bufferedCodeBuilder(CodeModel original);
 }

test/jdk/jdk/classfile/MethodBuilderStaticFlagTest.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2024, 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.
+ */
+
+import jdk.internal.classfile.impl.ChainedClassBuilder;
+import org.junit.jupiter.api.Test;
+
+import java.lang.classfile.ClassBuilder;
+import java.lang.classfile.ClassElement;
+import java.lang.classfile.ClassFile;
+import java.lang.classfile.ClassTransform;
+import java.lang.constant.ClassDesc;
+
+import static java.lang.classfile.ClassFile.ACC_PUBLIC;
+import static java.lang.classfile.ClassFile.ACC_STATIC;
+import static java.lang.constant.ConstantDescs.MTD_void;
+import static org.junit.jupiter.api.Assertions.*;
+
+/*
+ * @test
+ * @bug 8336777
+ * @summary Testing MethodBuilder correctly rejecting resetting the static
+ *          access flag.
+ * @run junit MethodBuilderStaticFlagTest
+ */
+class MethodBuilderStaticFlagTest {
+
+    void testClassBuilder(ClassBuilder clb) {
+        clb.withMethod("staticToStatic", MTD_void, ACC_STATIC, mb -> mb.withFlags(ACC_PUBLIC | ACC_STATIC));
+        assertThrows(IllegalArgumentException.class, () ->
+                clb.withMethod("staticToInstance", MTD_void, ACC_STATIC, mb -> mb.withFlags(ACC_PUBLIC)));
+        assertThrows(IllegalArgumentException.class, () ->
+                clb.withMethod("instanceToStatic", MTD_void, 0, mb -> mb.withFlags(ACC_PUBLIC | ACC_STATIC)));
+        clb.withMethod("instanceToInstance", MTD_void, 0, mb -> mb.withFlags(ACC_PUBLIC));
+    }
+
+    @Test
+    void testDirectBuilder() {
+        ClassFile.of().build(ClassDesc.of("C1"), this::testClassBuilder);
+    }
+
+    @Test
+    void testBufferedBuilder() {
+        var cf = ClassFile.of();
+        var bytes = cf.build(ClassDesc.of("C2"), _ -> {});
+        var cm = cf.parse(bytes);
+
+        cf.transformClass(cm, new ClassTransform() {
+            @Override
+            public void accept(ClassBuilder builder, ClassElement element) {
+                builder.with(element);
+            }
+
+            @Override
+            public void atEnd(ClassBuilder clb) {
+                assertInstanceOf(ChainedClassBuilder.class, clb);
+                testClassBuilder(clb);
+            }
+        }.andThen(ClassBuilder::with));
+    }
+}