Add support for sealed class attributes to ijar

See https://docs.oracle.com/javase/specs/jvms/se17/html/jvms-4.html#jvms-4.7.31

#13965

PiperOrigin-RevId: 401025676

third_party/ijar/classfile.cc

@@ -1302,6 +1302,30 @@ struct RecordAttribute : Attribute {
   std::vector<RecordComponentInfo *> components_;
 };
 
+// See JVMS §4.7.31
+struct PermittedSubclassesAttribute : Attribute {
+  static PermittedSubclassesAttribute *Read(const u1 *&p,
+                                            Constant *attribute_name) {
+    PermittedSubclassesAttribute *attr = new PermittedSubclassesAttribute;
+    attr->attribute_name_ = attribute_name;
+    u2 number_of_exceptions = get_u2be(p);
+    for (int ii = 0; ii < number_of_exceptions; ++ii) {
+      attr->permitted_subclasses_.push_back(constant(get_u2be(p)));
+    }
+    return attr;
+  }
+
+  void Write(u1 *&p) {
+    WriteProlog(p, permitted_subclasses_.size() * 2 + 2);
+    put_u2be(p, permitted_subclasses_.size());
+    for (size_t ii = 0; ii < permitted_subclasses_.size(); ++ii) {
+      put_u2be(p, permitted_subclasses_[ii]->slot());
+    }
+  }
+
+  std::vector<Constant *> permitted_subclasses_;
+};
+
 struct GeneralAttribute : Attribute {
   static GeneralAttribute* Read(const u1 *&p, Constant *attribute_name,
                                 u4 attribute_length) {
@@ -1503,6 +1527,9 @@ void HasAttrs::ReadAttrs(const u1 *&p) {
     } else if (attr_name == "Record") {
       attributes.push_back(
           RecordAttribute::Read(p, attribute_name, attribute_length));
+    } else if (attr_name == "PermittedSubclasses") {
+      attributes.push_back(
+          PermittedSubclassesAttribute::Read(p, attribute_name));
     } else if (attr_name == "com.google.devtools.ijar.KeepForCompile") {
       auto attr = new KeepForCompileAttribute;
       attr->attribute_name_ = attribute_name;

third_party/ijar/test/BUILD

@@ -35,6 +35,7 @@ sh_test(
         # TODO(cushon): build from source once we have a JDK 11
         "nestmates/nestmates.jar",
         "records/records.jar",
+        "sealed/sealed.jar",
         ":source_debug_extension.jar",
         ":keep_for_compile_lib.jar",
         ":largest_regular.jar",

third_party/ijar/test/ijar_test.sh

@@ -79,6 +79,8 @@ NESTMATES_JAR=$IJAR_SRCDIR/test/nestmates/nestmates.jar
 NESTMATES_IJAR=$TEST_TMPDIR/nestmates_interface.jar
 RECORDS_JAR=$IJAR_SRCDIR/test/records/records.jar
 RECORDS_IJAR=$TEST_TMPDIR/records_interface.jar
+SEALED_JAR=$IJAR_SRCDIR/test/sealed/sealed.jar
+SEALED_IJAR=$TEST_TMPDIR/sealed_interface.jar
 SOURCEDEBUGEXT_JAR=$IJAR_SRCDIR/test/source_debug_extension.jar
 SOURCEDEBUGEXT_IJAR=$TEST_TMPDIR/source_debug_extension.jar
 CENTRAL_DIR_LARGEST_REGULAR=$IJAR_SRCDIR/test/largest_regular.jar
@@ -545,6 +547,17 @@ function test_records_attribute() {
   expect_log "Record" "Records not preserved!"
 }
 
+function test_sealed_attribute() {
+  ls $IJAR $SEALED_JAR
+
+  # Check that Java 16 PermittedSubclasses attributes are preserved
+  $IJAR $SEALED_JAR $SEALED_IJAR || fail "ijar failed"
+
+  $JAVAP -classpath $SEALED_IJAR -v SealedTest >& $TEST_log \
+    || fail "javap failed"
+  expect_log "PermittedSubclasses" "PermittedSubclasses not preserved!"
+}
+
 function test_source_debug_extension_attribute() {
   # Check that SourceDebugExtension attributes are dropped without a warning
   $IJAR $SOURCEDEBUGEXT_JAR $SOURCEDEBUGEXT_IJAR >& $TEST_log || fail "ijar failed"

third_party/ijar/test/sealed/SealedTest.java

@@ -0,0 +1,22 @@
+// Copyright 2021 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+ /** A class that results in sealed attributes in Java 17. */
+sealed class SealedTest permits SealedTest.Foo, SealedTest.Bar {
+  static final class Foo extends SealedTest {
+  }
+
+  static final class Bar extends SealedTest {
+  }
+}