oracle/graal · error · IOException

Unknown type

Error message

Unknown type

What it means

While reading a PROPERTY_ARRAY property, BinaryReader reads a sub-type tag that selects the element encoding (PROPERTY_INT, PROPERTY_DOUBLE, PROPERTY_POOL). An unrecognized sub-type byte produces IOException('Unknown type'): the property section is malformed or was written by a producer using an array encoding this reader does not implement.

Source

Thrown at compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/BinaryReader.java:805

            case PROPERTY_DOUBLE:
                return dataSource.readDouble();
            case PROPERTY_TRUE:
                return Boolean.TRUE;
            case PROPERTY_FALSE:
                return Boolean.FALSE;
            case PROPERTY_POOL:
                return readPoolObject(Object.class);
            case PROPERTY_ARRAY:
                int subType = dataSource.readByte();
                switch (subType) {
                    case PROPERTY_INT:
                        return dataSource.readInts();
                    case PROPERTY_DOUBLE:
                        return dataSource.readDoubles();
                    case PROPERTY_POOL:
                        return readPoolObjects();
                    default:
                        throw new IOException("Unknown type");
                }
            case PROPERTY_SUBGRAPH:
                reporter.pushContext(ContextStrings::propertyGraph, key); // NOI18N
                builder.startNestedProperty(key);
                // will pop the name in its finally
                return parseGraph("", false);
            default:
                throw new IOException("Unknown type");
        }
    }

    private void closeDanglingGroups() throws IOException {
        while (folderLevel > 0) {
            // the builder may need to record the root position to close the group's entry
            builder.startRoot();
            doCloseGroup();
        }
        builder.end();

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Parse with a reader from the same or newer graphio version than the producer.
2. Regenerate the dump with a stock producer and retry.
3. If extending array encodings, add the case to both GraphProtocol writePropertyObject and BinaryReader readPropertyObject.

try { reader.parse(); } catch (IOException e) { if ("Unknown type".equals(e.getMessage())) { /* array property encoding unknown: upgrade reader or re-dump */ } }

When it happens

Trigger: A dump containing an array property whose sub-type byte is not one of int/double/pool; corrupt property data shifting the reader by one byte; a custom GraphProtocol extension emitting new array element types without reader support.

Common situations: Dumps from customized compilers, partial file transfers, or a reader older than the writer's array-property encoding.

Related errors

• Document properties unexpected in version < 7
• Invalid constant pool index :
• unknown klass type :
• unknown pool type
• File header is missing

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/63a6f7d26a1e0ced. Report an issue: GitHub.