oracle/graal · error · IllegalArgumentException

Expected an EspressoExternalObjectConstant, got {}

Error message

Expected an EspressoExternalObjectConstant, got {}

What it means

clonePrimitiveArray(primitiveArray) deep-copies a guest primitive array by unwrapping an EspressoExternalObjectConstant and calling the guest helper clonePrimitiveArray. A constant from any other JVMCI backend has no guest Value to clone, so it is rejected with IllegalArgumentException before the helper is invoked.

Source

Thrown at espresso-compiler-stub/src/com.oracle.truffle.espresso.vmaccess/src/com/oracle/truffle/espresso/vmaccess/EspressoExternalVMAccess.java:593

        return new EspressoExternalObjectConstant(this, array);
    }

    @Override
    public JavaConstant createPrimitiveArray(JavaKind kind, int length) {
        if (kind == null || !kind.isPrimitive() || kind == JavaKind.Void) {
            throw new IllegalArgumentException("Expected a non-void primitive kind, got " + kind);
        }
        if (length < 0) {
            throw new NegativeArraySizeException("Negative array size: " + length);
        }
        Value array = invokeJVMCIHelper("newPrimitiveArray", (int) kind.getTypeChar(), 1, length);
        return new EspressoExternalObjectConstant(this, array);
    }

    @Override
    public JavaConstant clonePrimitiveArray(JavaConstant primitiveArray) {
        if (!(primitiveArray instanceof EspressoExternalObjectConstant objectConstant)) {
            throw new IllegalArgumentException("Expected an EspressoExternalObjectConstant, got " + safeGetClass(primitiveArray));
        }
        EspressoResolvedObjectType arrayType = objectConstant.getType();
        if (!(arrayType.isArray() && arrayType.getComponentType().isPrimitive())) {
            throw new IllegalArgumentException("Expected a primitive array constant, got " + arrayType);
        }
        Value copy = invokeJVMCIHelper("clonePrimitiveArray", objectConstant.getValue());
        return new EspressoExternalObjectConstant(this, copy);
    }

    @Override
    public void copyArray(JavaConstant src, int srcPos, JavaConstant dest, int destPos, int length) {
        if (!(src instanceof EspressoExternalObjectConstant srcArray)) {
            throw new IllegalArgumentException("Expected an EspressoExternalObjectConstant for src, got " + safeGetClass(src));
        }
        if (!(dest instanceof EspressoExternalObjectConstant destArray)) {
            throw new IllegalArgumentException("Expected an EspressoExternalObjectConstant for dest, got " + safeGetClass(dest));
        }
        if (!srcArray.getType().isArray()) {

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Only clone arrays originally created by this Espresso provider (createPrimitiveArray / asArrayConstant results).
2. Guard with primitiveArray instanceof EspressoExternalObjectConstant and use host-side clone() for host arrays.
3. Keep constants tagged with their originating provider in caches to avoid cross-provider leakage.

Example fix

// before
JavaConstant copy = vmAccess.clonePrimitiveArray(maybeHostConstant);

// after
JavaConstant copy = (maybeHostConstant instanceof EspressoExternalObjectConstant)
        ? vmAccess.clonePrimitiveArray(maybeHostConstant)
        : hostCopy(maybeHostConstant);

if (!(primitiveArray instanceof EspressoExternalObjectConstant)) {
    // host array: clone on the host instead
}

static boolean isEspressoConstant(JavaConstant c) {
    return c instanceof EspressoExternalObjectConstant;
}

catch (IllegalArgumentException e) with 'Expected an EspressoExternalObjectConstant' -> clone host arrays with .clone(), guest arrays via the provider.

When it happens

Trigger: Passing a host-created array constant (JavaConstant.forObject(byte[]) or HotSpot constant) or a constant from another Espresso context to clonePrimitiveArray.

Common situations: Copy-on-write snapshot logic that sometimes receives host arrays; caching constants across provider lifecycles; tests with hand-built constants.

Related errors

• Invalid component type
• Element {} should be an espresso object constant, got {}
• Expected an EspressoExternalObjectConstant for src, got {}
• Expected an EspressoExternalObjectConstant for dest, got
• Expected an EspressoExternalObjectConstant, got

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/bb3fae899234c9bc. Report an issue: GitHub.