oracle/graal · error · RuntimeException

Error disassembling %s%nPartial disassembly:%n%s

Error message

Error disassembling %s%nPartial disassembly:%n%s

What it means

BytecodeDisassembler.disassemble wraps its whole decoding loop in a try/catch (Throwable) and rethrows a RuntimeException carrying the method descriptor plus the partial disassembly produced so far. Any failure while decoding an instruction or resolving a constant-pool operand (index out of range, unsupported opcode, malformed CP entry) is reported this way, with the original cause chained.

Source

Thrown at compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/bytecode/BytecodeDisassembler.java:252

                        buf.append(String.format("%4d: %-14s", bci, mnemonic));
                    } else {
                        buf.append(bci).append(' ').append(mnemonic);
                    }
                    if (stream.nextBCI() > bci + 1) {
                        if (!format) {
                            buf.append(' ');
                        }
                        decodeOperand(buf, stream, cp, method, bci, opcode);
                    }
                    if (newLine != null) {
                        buf.append(newLine);
                    }
                }
                stream.next();
                opcode = stream.currentBC();
            }
        } catch (Throwable e) {
            throw new RuntimeException(String.format("Error disassembling %s%nPartial disassembly:%n%s", method.format("%H.%n(%p)"), buf.toString()), e);
        }
        return buf.toString();
    }

    private void decodeOperand(StringBuilder buf, BytecodeStream stream, ConstantPool cp, ResolvedJavaMethod method, int bci, int opcode) {
        // @formatter:off
        switch (opcode) {
            case BIPUSH         : buf.append(stream.readByte()); break;
            case SIPUSH         : buf.append(stream.readShort()); break;
            case NEW            :
            case CHECKCAST      :
            case INSTANCEOF     :
            case ANEWARRAY      : {
                int cpi = stream.readCPI();
                JavaType type = cp.lookupType(cpi, opcode);
                cpi = cpiFunction.apply(opcode, cpi);
                if (format) {
                    buf.append(String.format("#%-10d // %s", cpi, type.toJavaName()));

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Read the chained cause (e.getCause()) — it names the actual decoding failure (e.g. ConstantPoolError, IndexOutOfBounds) and points at the failing instruction.
2. Disassemble the same class with javap -c or javap -v to confirm whether the class file itself is malformed; if javap also fails, the producer (obfuscator/agent) is at fault.
3. If javap succeeds, report a Graal issue with the method descriptor and partial disassembly from the message.
4. Upgrade Graal to a version matching the JDK's bytecode level if the class uses recently introduced instructions.

try {
    String dis = new BytecodeDisassembler().disassemble(method);
} catch (RuntimeException e) {
    if (e.getCause() != null) {
        LOG.warn("Disassembly failed at cause: {}", e.getCause());
    }
    // fall back to javap-style output or skip
}

When it happens

Trigger: Calling disassemble(method) on a ResolvedJavaMethod whose bytecode or constant pool is malformed or unexpected: bad CPI indices in operands, a tool (obfuscator/instrumentation agent) writing non-standard bytecode, or a disassembler gap for a newly added JVM instruction. The partial buffer in the message shows decoding progressed up to the failing BCI.

Common situations: Dumping bytecode during Graal debugging (-Dgraal.Dump triggers disassembly), disassembling classes processed by coverage tools, obfuscators, or ASM-based agents, or running a Graal build older than the JDK that produced the class files (new bytecodes). Frequently co-occurs with error 21's bridge scanning, which disassembles bridges.

Related errors

• multiline cannot be true when newLine is null
• Couldn't find method bridged by %s:%n%s
• No opcode for %s
• Could not connect to the IGV on %s:%d
• Failed to open %s to dump IGV graphs

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/e3310098de3529c1. Report an issue: GitHub.