8252031: --patch-module java.base= may fail with \"cyclic inheritance involving Object\"

Avoiding clash in use of Flags.LOCKED between Types.asSuper and Check.checkNonCyclic.

Reviewed-by: jjg

src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java

@@ -2115,6 +2115,8 @@ public class Types {
     // where
         private SimpleVisitor<Type,Symbol> asSuper = new SimpleVisitor<Type,Symbol>() {
 
+            private Set<Symbol> seenTypes = new HashSet<>();
+
             public Type visitType(Type t, Symbol sym) {
                 return null;
             }
@@ -2125,11 +2127,10 @@ public class Types {
                     return t;
 
                 Symbol c = t.tsym;
-                if ((c.flags_field & LOCKED) != 0) {
+                if (!seenTypes.add(c)) {
                     return null;
                 }
                 try {
-                    c.flags_field |= LOCKED;
                     Type st = supertype(t);
                     if (st.hasTag(CLASS) || st.hasTag(TYPEVAR)) {
                         Type x = asSuper(st, sym);
@@ -2147,7 +2148,7 @@ public class Types {
                     }
                     return null;
                 } finally {
-                    c.flags_field &= ~LOCKED;
+                    seenTypes.remove(c);
                 }
             }
 

test/langtools/tools/javac/flags/LockedFlagClash.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2020, 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 8252031
+ * @summary Verify the use of Flags.LOCKED in Check.checkNonCyclic is not broken
+            by use in Types.asSuper.
+ * @library /tools/lib
+ * @modules jdk.compiler/com.sun.tools.javac.api
+ * @build toolbox.JavacTask toolbox.TestRunner toolbox.ToolBox
+ * @run main LockedFlagClash
+ */
+
+import java.io.IOException;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+import toolbox.JavacTask;
+import toolbox.TestRunner;
+import toolbox.ToolBox;
+
+public class LockedFlagClash extends TestRunner {
+
+    public static void main(String... args) throws Exception {
+        LockedFlagClash t = new LockedFlagClash();
+        t.runTests();
+    }
+
+    private final ToolBox tb = new ToolBox();
+
+    LockedFlagClash() throws IOException {
+        super(System.err);
+    }
+
+    protected void runTests() throws Exception {
+        runTests(m -> new Object[] { Paths.get(m.getName()) });
+    }
+
+    @Test
+    public void testLOCKEDFlagDoesNotClash(Path base) throws Exception {
+        Path src = base.resolve("src");
+        tb.writeJavaFiles(src,
+                          """
+                          package java.lang;
+                          public abstract class Byte extends Number {
+                          }
+                          """,
+                          """
+                          package java.lang;
+                          public class Object {
+                          }
+                          """,
+                          """
+                          package java.lang;
+                          public class Test {
+                              private static final String o1 = "";
+                              private static final String o2 = "" + o1;
+                          }
+                          """);
+        Path classes = base.resolve("classes");
+
+        tb.createDirectories(classes);
+        tb.cleanDirectory(classes);
+
+        new JavacTask(tb)
+                .outdir(classes)
+                .options("--patch-module", "java.base=" + src)
+                .files(tb.findJavaFiles(src.resolve("java").resolve("lang").resolve("Test.java")))
+                .run()
+                .writeAll();
+    }
+}