[Native Image, WASM] Calling java.time.chrono.Chronology.getAvailableChronologies() results in a java.lang.NullPointerException

[treblereel]

Describe the Issue

When I call java.time.chrono.Chronology.getAvailableChronologies(), for example like this:

`
import java.time.chrono.Chronology;

public class App {

public static void main(String[] args) throws IOException {

for(Chronology chronology : Chronology.getAvailableChronologies()) {
  System.out.println(chronology.getId() + " - " + chronology.getClass().getName());
}

}

}
`
it results in a NullPointerException.

Using the latest version of GraalVM can resolve many issues.

• I tried with the latest version of GraalVM.

GraalVM Version

java version "25" 2025-09-16 LTS
Java(TM) SE Runtime Environment Oracle GraalVM 25-dev+25.1 (build 25+25-LTS-jvmci-b01)
Java HotSpot(TM) 64-Bit Server VM Oracle GraalVM 25-dev+25.1 (build 25+25-LTS-jvmci-b01, mixed mode, sharing)

Operating System and Version

OSX 15.4.1 (24E263)

Troubleshooting Confirmation

• I tried the suggestions in the troubleshooting guide.

Run Command

it's maven setup:

app.zip

Expected Behavior

no NPE exception

Actual Behavior

java.lang.NullPointerException

Steps to Reproduce

1. mvn clean package -Pwasm
2. run http-server at web folder
3. open broswer localhost:8080
4. check console

Additional Context

Maybe it's somehow connected with ServiceLoader:

static Set getAvailableChronologies() {
initCache(); // force initialization
HashSet chronos = new HashSet<>(CHRONOS_BY_ID.values());

    /// Add in Chronologies from the ServiceLoader configuration
    ServiceLoader<Chronology> loader = ServiceLoader.load(Chronology.class);
    for (Chronology chrono : loader) {
        chronos.add(chrono);
    }
    return chronos;
}

but it's part of java

Run-Time Log Output and Error Messages

app.js:266 Exception in thread "main" java.lang.ExceptionInInitializerError

app.js:266 at genBacktrace (http://127.0.0.1:8080/app.js:1229:12)
app.js:266 at genBacktrace (http://127.0.0.1:8080/app.js:1299:32)
app.js:266 at _ClassInitializationInfo_doInitialize___ClassInitializationInfo_Class_V (wasm://wasm/02706d1a:wasm-function[918]:0x15c5f6)
app.js:266 at ClassInitializationInfo_slowPath___ClassInitializationInfo_Class_V (wasm://wasm/02706d1a:wasm-function[1329]:0x16da12)
app.js:266 at AbstractChronology_initCache___Z (wasm://wasm/02706d1a:wasm-function[9422]:0x2cdf23)
app.js:266 at AbstractChronology_getAvailableChronologies___Set (wasm://wasm/02706d1a:wasm-function[9430]:0x2ce667)
app.js:266 at App_main$Ljava_lang_String__V (wasm://wasm/02706d1a:wasm-function[9475]:0x2d0991)
app.js:266 at WebImageJavaMainSupport_doRun$Ljava_lang_String__WebImageJavaMainSupport$Runner_I (wasm://wasm/02706d1a:wasm-function[586]:0x14b8da)
app.js:266 at WebImageWasmGCJavaMainSupport_run$Ljava_lang_String__I (wasm://wasm/02706d1a:wasm-function[1132]:0x16677f)
app.js:266 Caused by: java.lang.NullPointerException
app.js:266 at genBacktrace (http://127.0.0.1:8080/app.js:1229:12)
app.js:266 at genBacktrace (http://127.0.0.1:8080/app.js:1299:32)
app.js:266 at _ImplicitExceptions_throwNewNullPointerException___V (wasm://wasm/02706d1a:wasm-function[1309]:0x16cab2)
app.js:266 at _PathService$1_apply___Object_Z (wasm://wasm/02706d1a:wasm-function[8872]:0x2a47cc)
app.js:266 at _Iterators$5_computeNext___Object (wasm://wasm/02706d1a:wasm-function[7524]:0x259ddd)
app.js:266 at func.bridge._AbstractIterator.computeNext___Object (wasm://wasm/02706d1a:wasm-function[3190]:0x183321)
app.js:266 at _AbstractIterator_hasNext___Z (wasm://wasm/02706d1a:wasm-function[7526]:0x259f30)
app.js:266 at func.bridge._Iterator.hasNext___Z (wasm://wasm/02706d1a:wasm-function[3686]:0x185527)
app.js:266 at _Joiner_appendTo___Appendable_Iterator_Appendable (wasm://wasm/02706d1a:wasm-function[4023]:0x1939b8)


[selhagani]

Hi @treblereel,

Thank you for reaching out to us about this.
Could you please try using the tracing agent to generate the configuration files to see if that will help solve your issue? More information about the tracing agent can be found here https://www.graalvm.org/latest/reference-manual/native-image/metadata/AutomaticMetadataCollection/

[patrick96]

The NPE seems to be a general Native Image issue, see #11410

This can be worked around by passing -Djava.home= to the program's commandline arguments.
You will also need to pass add the -H:+ParseRuntimeOptions build option for native image, otherwise the -D arguments get ignored.

I don't know how you're launching the wrapper JS file that the Wasm backend generates, but if you use the default flags, the backend will generate some auto-run code, where it tries to read the commandline arguments from the environment (it first looks at process.argv[2:] and then at scriptArgs).

If you want to pass your own args, you have to build with -H:-AutoRunVM and run the code yourself:

GraalVM.run(["your", "args"]).catch(console.error);

[treblereel]

@patrick96
Thank you very much for your time. It looks like this isn't a WASM-specific issue, but rather a general Graal problem, so I think it's reasonable to close this issue. I’d also like to add that since this is part of the standard library, in my opinion, users shouldn’t be expected to take any special steps to make it work.

Thanks again for your help