NationalSecurityAgency/ghidra · error · IllegalArgumentException

Cannot rewind a negative number

Error message

Cannot rewind a negative number

What it means

Sequence.rewind throws when called with a negative count. Rewinding means removing the given number of steps from the end of the sequence; a negative count is logically meaningless. The method modifies the sequence in place, reducing each step's tick count from the tail until the requested count is consumed.

Source

Thrown at Ghidra/Debug/Framework-TraceModeling/src/main/java/ghidra/trace/model/time/schedule/Sequence.java:188

		for (; toRemove > 0; toRemove--) {
			steps.remove(steps.size() - 1);
		}
	}

	/**
	 * Rewind this sequence the given step count
	 * 
	 * <p>
	 * This modifies the sequence in place, removing the given count from the end of the sequence.
	 * Any step whose count is reduced to 0 as a result of rewinding is removed entirely from the
	 * sequence. Note that each sleigh step (modification) counts as one step when rewinding.
	 * 
	 * @param count the step count to rewind
	 * @return if count exceeds the steps of this sequence, the (positive) difference remaining
	 */
	public long rewind(long count) {
		if (count < 0) {
			throw new IllegalArgumentException("Cannot rewind a negative number");
		}
		while (!steps.isEmpty()) {
			int lastIndex = steps.size() - 1;
			count = steps.get(lastIndex).rewind(count);
			if (count >= 0) {
				steps.remove(lastIndex);
			}
			if (count <= 0) {
				break;
			}
		}
		return Long.max(0, count);
	}

	/**
	 * Drop the last step from this sequence
	 * 
	 * @return the sequence with the last step removed

View on GitHub (pinned to d5f144c24d)

Solutions

1. Clamp the count to zero before calling: rewind(Math.max(0, count))
2. Check the sign before calling: if (count >= 0) sequence.rewind(count)
3. If computing a delta between two sequences, ensure the result is non-negative or use Long.max(0, delta)

Example fix

// before
sequence.rewind(delta); // delta may be negative
// after
if (delta > 0) {
    sequence.rewind(delta);
}

long safeCount = Math.max(0, requestedCount);
if (safeCount > 0) {
    sequence.rewind(safeCount);
}

// N/A — primitive long, guard with range check

try {
    sequence.rewind(count);
} catch (IllegalArgumentException e) {
    // clamp count to 0 and retry, or report
    sequence.rewind(0);
}

When it happens

Trigger: Calling sequence.rewind(negativeNumber) directly, or calling it with a value computed from a subtraction that can go negative (e.g. rewind(this.getTotalTickCount() - other.getTotalTickCount()) when this has fewer ticks than other).

Common situations: Diffing two schedules and rewinding by the delta without clamping to zero. Using rewind in a loop where the count variable is decremented past zero by external logic.

Related errors

• The given prefix (%s) is not actually a prefix of this (%s).
• Thread must be given, e.g., 0:t1-3, since the last thread or
• Thread with key %d does not exist in given trace
• Cannot have instructions steps following p-code steps
• Cannot parse step: '

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/9d369fb549c24818. Report an issue: GitHub.