skylot/jadx · error · CodegenException

Unknown instruction:

Error message

Unknown instruction: 

What it means

Thrown by InsnGen.makeInsnBody() as the default branch of the large switch on insn.getType(). The switch covers dozens of InsnType values (CONST_STR, INVOKE, MOVE, etc.) plus the legacy JAVA_JSR and JAVA_RET fallback cases. Reaching the default means an instruction type is not handled — either a new InsnType was added without a case, or internal state produced an unexpected type.

Source

Thrown at jadx-core/src/main/java/jadx/core/codegen/InsnGen.java:649

					code.add(" = ");
					addArg(code, insn.getArg(i + 1));
					code.add("; ");
				}
				break;

			case JAVA_JSR:
				fallbackOnlyInsn(insn);
				code.add("jsr -> ").add(MethodGen.getLabelName(((JsrNode) insn).getTarget()));
				break;

			case JAVA_RET:
				fallbackOnlyInsn(insn);
				code.add("ret ");
				addArg(code, insn.getArg(0));
				break;

			default:
				throw new CodegenException(mth, "Unknown instruction: " + insn.getType());
		}
	}

	/**
	 * In most cases must be combined with new array instructions.
	 * Use one by one array fill (can be replaced with System.arrayCopy)
	 */
	private void fillArray(ICodeWriter code, FillArrayInsn arrayNode) throws CodegenException {
		if (mth.checkCommentsLevel(CommentsLevel.INFO)) {
			code.add("// fill-array-data instruction");
		}
		code.startLine();
		InsnArg arrArg = arrayNode.getArg(0);
		ArgType arrayType = arrArg.getType();
		ArgType elemType;
		if (arrayType.isTypeKnown() && arrayType.isArray()) {
			elemType = arrayType.getArrayElement();
		} else {

View on GitHub (pinned to e738a26571)

Solutions

1. If you added a new InsnType, add a matching case in makeInsnBody().
2. Update jadx to the latest version where more instruction types may be handled.
3. Report the class and instruction type to the jadx issue tracker.

try {
    insnGen.makeInsn(insn, code);
} catch (CodegenException e) {
    if (e.getMessage().startsWith("Unknown instruction")) {
        code.startLine("// jadx: unknown instruction type: " + insn.getType());
        logger.warn("Unknown instruction type in codegen", e);
        // Continue with next instruction
    } else {
        throw e;
    }
}

When it happens

Trigger: An InsnNode with an InsnType value not covered by the switch. Adding a new instruction type to InsnType without adding a case in makeInsnBody(). Corrupted instruction nodes with wrong type tags.

Common situations: Contributing new instruction support to jadx without updating makeInsnBody(). Rare in normal use — typically a development-time guard. Some uncommon bytecode patterns may produce instructions that reach this point in older jadx versions.

Related errors

• Unknown arg type
• Unknown output format
• Unknown condition mode:
• Unknown loop type:
• Unexpected field type class:

AI-assisted analysis of skylot/jadx@e738a26571 (2026-08-14). Data as JSON: /api/errors/6832d3737c0d8309. Report an issue: GitHub.