So, trying to run a simple "hello-world" type of clojure app - it compiles using native-image, but when I run it, I get this:

Exception in thread "main" java.lang.ExceptionInInitializerError
	at com.oracle.svm.core.hub.ClassInitializationInfo.initialize(ClassInitializationInfo.java:287)
	at java.lang.Class.ensureInitialized(DynamicHub.java:437)
	at clojure.lang.Namespace.<init>(Namespace.java:34)
	at clojure.lang.Namespace.findOrCreate(Namespace.java:176)
	at clojure.lang.Var.internPrivate(Var.java:153)
	at palindrome.core.<clinit>(Unknown Source)
	at com.oracle.svm.core.hub.ClassInitializationInfo.invokeClassInitializer(ClassInitializationInfo.java:347)
	at com.oracle.svm.core.hub.ClassInitializationInfo.initialize(ClassInitializationInfo.java:267)
	at java.lang.Class.ensureInitialized(DynamicHub.java:437)
Caused by: java.io.FileNotFoundException: Could not locate clojure/core__init.class or clojure/core.clj on classpath.
	at clojure.lang.RT.load(RT.java:463)
	at clojure.lang.RT.load(RT.java:426)
	at clojure.lang.RT.doInit(RT.java:468)
	at clojure.lang.RT.<clinit>(RT.java:336)
	at com.oracle.svm.core.hub.ClassInitializationInfo.invokeClassInitializer(ClassInitializationInfo.java:347)
	at com.oracle.svm.core.hub.ClassInitializationInfo.initialize(ClassInitializationInfo.java:267)
	... 8 more

Puzzling!

I'm building the app using

GraalVM Version 19.0.0 CE

Anyone else come up against this issue?

The solution to my problem was to add (flush) at the end of the program that worked

Okay, found the answer. With GraalVM 19.0.0, they have changed the way that classes are initialised at runtime

It's all clearly detailed in their release notes for 19.0.0

https://www.graalvm.org/docs/release-notes/

To fix the problem, and to have the native-image run perfectly, you just have to do this (showing an example project.clj)

(defproject palindrome "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url ""
  :license {:name "EPL-2.0 OR GPL-2.0-or-later WITH Classpath-exception-2.0"
            :url ""}
  :dependencies [[org.clojure/clojure "1.9.0"]]
  :plugins [[io.taylorwood/lein-native-image "0.3.0"]]
  :native-image {:name "palindromes"
                 :opts ["--report-unsupported-elements-at-runtime"
                        "--initialize-at-build-time"]}
  :main ^:skip-aot palindrome.core
  :repl-options {:init-ns palindrome.core}
  :profiles {:dev {:global-vars {*warn-on-reflection* true
                                 *assert* true}}
             :uberjar {:aot 
                       :all
                       :native-image {:jvm-opts ["-Dclojure.compiler.direct-linking=true"]}}})

The incantation is to add in the --initialize-at-build-time flag for graalvm to do it's magic.

A very quick and-take-it-with-a-pinch-of-salt-metric

java -jar target/palindrome-0.1.0-SNAPSHOT-standalone.jar "foo"  2.35s user 0.27s system 225% cpu 1.161 total

verses:

./target/palindromes "foo"  0.01s user 0.00s system 88% cpu 0.006 total

0.01s for the native image!!!

w00t

hope this helps others... 🙂

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