[lworld] RFR: JDK-8247795 allow factory methods for inline types to return j.l.Obje…

[Mandy Chung]

On Fri, 19 Jun 2020 13:08:44 GMT, Harold Seigel <hseigel at openjdk.org> wrote:

> Expect the return type for the <init> factory methods of hidden inline classes to return type java.lang.Object.  Also,
> fix issue so that Reflection::new_constructor(), not new_method(), is called for <init> factory methods.

src/hotspot/share/classfile/classFileParser.cpp line 2482:

> 2481:         const Symbol* required = class_name();
> 2482:         if (is_hidden() || is_unsafe_anonymous()) {
> 2483:           // The original class name in hidden classes and in the UAC byte stream gets

JDK no longer uses VM anonymous class.   This check (when parsing the static factory method of an inline type) should
be updated to `if (is_hidden())` and drop `is_unsafe_anonymous()`.

src/hotspot/share/runtime/reflection.cpp line 1226:

> 1225:     BasicType rtype;
> 1226:     if (klass->is_hidden() || klass->is_unsafe_anonymous()) {
> 1227:       rtype = T_OBJECT;

Drop `is_unsafe_anonymous` check.   We should not support VM anonymous class be an inline type.

I suggest to add a comment to explain this workarounds the JVM spec issue for hidden classes.

test/hotspot/jtreg/runtime/valhalla/valuetypes/HiddenInlineClassTest.java line 48:

> 47:     static byte[] readClassFile(String classFileName) throws Exception {
> 48:         File classFile = new File(CLASSES_DIR + File.separator + classFileName);
> 49:         try (FileInputStream in = new FileInputStream(classFile);

A simpler implementation is to use NIO:
    static final Path CLASSES_DIR = Paths.get(System.getProperty("test.classes", "."));

    static byte[] readClassFile(String cn) throws IOException {
        Path path = CLASSES_DIR.resolve(cn.replace('.', File.separatorChar) + ".class");
        return Files.readAllBytes(path);
    }

test/hotspot/jtreg/runtime/valhalla/valuetypes/HiddenInlineClassTest.java line 65:

> 64:         Class<?> c = lookup.defineHiddenClass(bytes, true, NESTMATE).lookupClass();
> 65:         Object hp = c.newInstance();
> 66:         String s = (String)c.getMethod("getValue").invoke(hp);

Nit: No need to be a nestmate.

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PR: https://git.openjdk.java.net/valhalla/pull/94