NationalSecurityAgency/ghidra · error · IllegalArgumentException

Cannot have instructions steps following p-code steps

Error message

Cannot have instructions steps following p-code steps

What it means

TraceSchedule.advanced combines this schedule with a 'next' schedule to produce a continued schedule. If this schedule already has p-code steps (pSteps is non-empty), and the next schedule has instruction/tick steps (steps is non-empty), the combination is illegal — p-code steps cannot be followed by instruction steps because that would require emulating backwards from p-code to instruction level. Only p-code-after-p-code or instruction-after-instruction continuations are valid.

Source

Thrown at Ghidra/Debug/Framework-TraceModeling/src/main/java/ghidra/trace/model/time/schedule/TraceSchedule.java:892

	 * schedule contains any p-code steps and {@code next} has instruction steps, an error will be
	 * 
	 * @param next the schedule to append. Its snap is ignored.
	 * @return the complete schedule
	 * @throws IllegalArgumentException if the result would have instruction steps following p-code
	 *             steps
	 */
	public TraceSchedule advanced(TraceSchedule next) {
		if (this.pSteps.isNop()) {
			Sequence ticks = this.steps.clone();
			ticks.advance(next.steps);
			return new TraceSchedule(this.snap, ticks, next.pSteps.clone(), next.source);
		}
		else if (next.steps.isNop()) {
			Sequence pTicks = this.pSteps.clone();
			pTicks.advance(next.pSteps);
			return new TraceSchedule(this.snap, this.steps.clone(), pTicks, Source.INPUT);
		}
		throw new IllegalArgumentException("Cannot have instructions steps following p-code steps");
	}

	/**
	 * Drop the p-code steps
	 * 
	 * @return the schedule without ops
	 */
	public TraceSchedule dropPSteps() {
		return new TraceSchedule(this.snap, this.steps, new Sequence());
	}

	/**
	 * Drop the last step
	 * 
	 * <p>
	 * If there are p-code steps, this drops the last step there. Otherwise, this drops the last
	 * step from the instruction steps. A step includes all ticks in the step, e.g.,
	 * {@code 0:t0-20;t1-5} becomes {@code 0:t0-20}. To remove a specific number of ticks, see

View on GitHub (pinned to d5f144c24d)

Solutions

1. If this schedule has pSteps, only advance with a next schedule that also has only pSteps (next.steps must be nop)
2. Drop the pSteps from this schedule first: schedule = schedule.dropPSteps(), then advance
3. Restructure the schedule so all instruction steps come before all p-code steps
4. Use schedule.finishPcodeStep() or equivalent to normalize before advancing

Example fix

// before
TraceSchedule base = TraceSchedule.parse("0:t1-5.t2-1", Source.INPUT, TimeRadix.DEC);
TraceSchedule next = TraceSchedule.parse("0:t1-3", Source.INPUT, TimeRadix.DEC);
TraceSchedule combined = base.advanced(next); // throws
// after
TraceSchedule base = TraceSchedule.parse("0:t1-5.t2-1", Source.INPUT, TimeRadix.DEC);
TraceSchedule next = TraceSchedule.parse("0:.t2-1", Source.INPUT, TimeRadix.DEC); // pSteps only
TraceSchedule combined = base.advanced(next);

boolean canAdvance(TraceSchedule base, TraceSchedule next) {
    if (!base.pSteps.isNop() && !next.steps.isNop()) {
        return false; // instruction steps after p-code steps
    }
    return true;
}

// N/A

try {
    TraceSchedule combined = base.advanced(next);
} catch (IllegalArgumentException e) {
    // drop pSteps and retry, or restructure the schedule
    TraceSchedule combined = base.dropPSteps().advanced(next);
}

When it happens

Trigger: Calling schedule.advanced(next) where schedule has pSteps and next has steps (instruction steps). This happens when you first advance into p-code stepping (the '.' portion) and then try to append an instruction-level step.

Common situations: Building composite schedules from multiple user actions where the user first steps at p-code level then tries to step at instruction level. Merging schedule bookmarks that were recorded at different emulation granularities. Attempting to create a schedule that mixes instruction and p-code steps in an invalid order.

Related errors

• Cannot rewind a negative number
• 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 parse step: '

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/e2f1e194e98a640d. Report an issue: GitHub.