cmdjulian / graal-is-assigable-buggy

Bug Report for GraalVM for JDK 21

Showcase a bug where native image behaves different from the JVM where .isAssignableFrom(someClazz) delivers a different result than the JVM. This only happens for optimization levels greater than -O0.

To reproduce, run ./gradlew test and see a successful JVM run. Now run ./gradlew nativeTest and see a raised error: java.lang.IllegalArgumentException: Unsupported response type: [B.

This is due to the fact that now for the following simplified code, the isAssignableFrom(type) is not taken anymore:

enum SupportedResponses {
  TEXT(String.class), INPUT_STREAM(InputStream.class), READER(Reader.class), BYTE_ARRAY(byte[].class);

  private final Class<?> type;

  <T> SupportedResponses(Class<T> type) {
    this.type = type;
  }

  public static SupportedResponses from(Class<?> type) {
    for (SupportedResponses sr : SupportedResponses.values()) {
      if (sr.type.isAssignableFrom(type)) {
        return sr;
      }
    }
    throw new IllegalArgumentException("Unsupported response type: " + type.getName());
  }
}

Raised issue is java.lang.IllegalArgumentException: Unsupported response type: [B.

You can find the issue at oracle/graal#7966