Re: RFR: 8323832: Load JVMCI with the platform class loader [v2]

[Doug Simon]

On Wed, 24 Jan 2024 06:11:30 GMT, David Holmes <dhol...@openjdk.org> wrote:

> I'm still puzzled by the need to do this as any non-delegating classloader 
> would have allowed this even if JVMCI were loaded by the bootloader.

As far as I understand, even a non-delegating classloader cannot redefine a 
class loaded by the boot loader. I modified the test to show this and get:

java.lang.LinkageError: loader LoadAlternativeJVMCI$1 @4a1f4d08 attempted 
duplicate class definition for jdk.vm.ci.meta.ResolvedJavaType. 
(jdk.vm.ci.meta.ResolvedJavaType is in unnamed module of loader 
LoadAlternativeJVMCI$1 @4a1f4d08, parent loader 'bootstrap')
        at java.base/java.lang.ClassLoader.defineClass1(Native Method)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1023)
        at 
java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
        at 
java.base/java.net.URLClassLoader.defineClass(URLClassLoader.java:524)
        at java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:427)
        at java.base/java.net.URLClassLoader$1.run(URLClassLoader.java:421)
        at 
java.base/java.security.AccessController.doPrivileged(AccessController.java:714)
        at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:420)
        at LoadAlternativeJVMCI$1.loadClass(LoadAlternativeJVMCI.java:61)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:525)
        at LoadAlternativeJVMCI.main(LoadAlternativeJVMCI.java:77)
        at 
java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
        at java.base/java.lang.reflect.Method.invoke(Method.java:580)
        at 
com.sun.javatest.regtest.agent.MainWrapper$MainTask.run(MainWrapper.java:138)
        at java.base/java.lang.Thread.run(Thread.java:1575)


Test modification:

diff --git a/test/hotspot/jtreg/compiler/jvmci/LoadAlternativeJVMCI.java 
b/test/hotspot/jtreg/compiler/jvmci/LoadAlternativeJVMCI.java
index dd63867e7c2..28a6fedca38 100644
--- a/test/hotspot/jtreg/compiler/jvmci/LoadAlternativeJVMCI.java
+++ b/test/hotspot/jtreg/compiler/jvmci/LoadAlternativeJVMCI.java
@@ -51,7 +51,14 @@ public static void main(String[] args) throws Exception {
         }

         ClassLoader pcl = ClassLoader.getPlatformClassLoader();
-        URLClassLoader ucl = new URLClassLoader(cp, null);
+        URLClassLoader ucl = new URLClassLoader(cp, null) {
+            protected Class<?> loadClass(String name, boolean resolve) throws 
ClassNotFoundException {
+                if (!name.startsWith("jdk.vm.ci")) {
+                    return super.loadClass(name, resolve);
+                }
+                return findClass(name);
+            }
+        };

         String[] names = {
             "jdk.vm.ci.meta.ResolvedJavaType",

-------------

PR Comment: https://git.openjdk.org/jdk/pull/17520#issuecomment-1907671987