oracle/graal · error · IllegalArgumentException

Unknown jump table entry format:

Error message

Unknown jump table entry format: 

What it means

HexCodeFileDis throws this IllegalArgumentException when rendering a jump table whose entryFormat is neither OFFSET nor KEY2_OFFSET. Jump-table metadata embedded in a HexCodeFile describes how each entry encodes its target (plain 4-byte offset, or key2 plus offset); an unknown enum constant means the file's jump-table annotation uses a format this parser version does not understand. It is a data/version mismatch, not a runtime decoding failure.

Source

Thrown at compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/disassembler/HexCodeFileDis.java:163

                EntryFormat entryFormat = jumpTable.entryFormat;
                int entrySize = entryFormat.size;
                Instruction lastInsn = insns.get(insns.size() - 1);
                long entries = Math.abs(jumpTable.high - (long) jumpTable.low);
                for (int i = 0; i <= entries; i++) {
                    int entryOffset = jumpTable.getPosition() + i * entrySize;
                    Integer secondaryKey;
                    int targetOffsetRelativeToJumpTable;
                    switch (jumpTable.entryFormat) {
                        case OFFSET:
                            secondaryKey = null;
                            targetOffsetRelativeToJumpTable = readInt(dis.isLittleEndian(), hcf.code, entryOffset);
                            break;
                        case KEY2_OFFSET:
                            secondaryKey = readInt(dis.isLittleEndian(), hcf.code, entryOffset);
                            targetOffsetRelativeToJumpTable = readInt(dis.isLittleEndian(), hcf.code, entryOffset + 4);
                            break;
                        default:
                            throw new IllegalArgumentException("Unknown jump table entry format: " + jumpTable.entryFormat);
                    }
                    int primaryKey = jumpTable.low + i;
                    long target = hcf.startAddress + jumpTableOffset + targetOffsetRelativeToJumpTable;
                    lastInsn.jumpTable.add(new JumpTableEntry(entryOffset, hcf.startAddress + entryOffset, primaryKey, secondaryKey, target));

                }
                long newStartOffset = jumpTableOffset + entrySize * (jumpTable.high - (long) jumpTable.low + 1);
                startOffset = (int) newStartOffset;
                assert startOffset == newStartOffset;
            }
            if (startOffset < hcf.code.length) {
                for (Instruction i : disassembleAtOffset(hcf, dis, startOffset, hcf.code.length)) {
                    instructionMap.put(i.getOffset(), i);
                }
            }
        }

        Width labelWidth = new Width(1);

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Use a disassembler version matched to the GraalVM that produced the dump.
2. If you control the annotation, set the jump-table format to a supported value (OFFSET or KEY2_OFFSET).
3. If adding a new format, extend this switch with a decoding branch before shipping dumps that use it.
4. Strip or correct the jump-table metadata lines from the hex file to fall back to plain linear disassembly.

Example fix

// before (metadata line in hex file)
# jump_table: format=UNKNOWN fmt=...
// after
# jump_table: format=OFFSET ...

if (jumpTable.entryFormat != EntryFormat.OFFSET && jumpTable.entryFormat != EntryFormat.KEY2_OFFSET) {
    // skip jump-table rendering, fall back to linear disassembly of the region
}

try { renderJumpTable(jt); } catch (IllegalArgumentException e) { /* unknown format: disassemble region linearly instead */ }

When it happens

Trigger: Disassembling a HexCodeFile that carries a jump-table comment/metadata block declaring an entry format constant added in a newer (or removed) GraalVM version, while jumpTable.entryFormat parses to something outside the two handled cases. Also triggered by hand-authored jump-table annotations with a wrong format token.

Common situations: Disassembling dumps produced by a newer GraalVM that introduced a new entry format (e.g. 8-byte offsets) with an older disassembler library, or vice versa after a format constant was renamed.

Related errors

• Unsupported replay file version
• Malformed HexCodeFile in
• Unable to decode some instructions in
• Malformed HexCodeFile in
• Unsupported ISA:

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/fe3371c8123c375a. Report an issue: GitHub.