NationalSecurityAgency/ghidra · error · IllegalArgumentException

Trace must use a sleigh-based language

Error message

Trace must use a sleigh-based language

What it means

evaluateBytes(String expr, ...) compiles a Sleigh source expression on the trace's base language, then evaluates it. Compilation requires a SleighLanguage; if trace.getBaseLanguage() is any other Language subclass, it cannot compile and is rejected.

Source

Thrown at Ghidra/Debug/Framework-TraceModeling/src/main/java/ghidra/pcode/exec/trace/TraceSleighUtils.java:225

			Utils.bytesToBigInteger(bytes, bytes.length, expr.getLanguage().isBigEndian(), false),
			bytesPair.getRight());
	}

	/**
	 * Evaluate a Sleigh expression on the given trace
	 * 
	 * @param expr the expression
	 * @param trace the trace
	 * @param snap the snap
	 * @param thread the thread, required if register space is used
	 * @param frame the frame, for when register space is used
	 * @return the value of the expression as a byte array
	 */
	public static byte[] evaluateBytes(String expr, Trace trace, long snap, TraceThread thread,
			int frame) {
		Language language = trace.getBaseLanguage();
		if (!(language instanceof SleighLanguage)) {
			throw new IllegalArgumentException("Trace must use a sleigh-based language");
		}
		return evaluateBytes(
			SleighProgramCompiler.compileExpression((SleighLanguage) language, expr),
			trace, snap, thread, frame);
	}

	/**
	 * Evaluate a Sleigh expression on the given trace
	 * 
	 * @param expr the expression
	 * @param trace the trace
	 * @param snap the snap
	 * @param thread the thread, required if register space is used
	 * @param frame the frame, for when register space is used
	 * @return the value of the expression as a big integer
	 */
	public static BigInteger evaluate(String expr, Trace trace, long snap, TraceThread thread,
			int frame) {

View on GitHub (pinned to d5f144c24d)

Solutions

1. Ensure the trace's base language resolves to a SleighLanguage (correct LanguageID / .ldefs).
2. Prefer the PcodeExpression overload and compile yourself only when you have confirmed a Sleigh language.
3. Guard: `if (trace.getBaseLanguage() instanceof SleighLanguage)` before calling.

Example fix

// before
byte[] v = TraceSleighUtils.evaluateBytes("inst_start", trace, snap, thread, frame);

// after
if (!(trace.getBaseLanguage() instanceof SleighLanguage)) {
    throw new IllegalStateException("trace language is not Sleigh: " + trace.getBaseLanguage());
}
byte[] v = TraceSleighUtils.evaluateBytes("inst_start", trace, snap, thread, frame);

if (!(trace.getBaseLanguage() instanceof SleighLanguage)) {
    throw new IllegalStateException("trace not Sleigh: " + trace.getBaseLanguage());
}
byte[] v = TraceSleighUtils.evaluateBytes(exprText, trace, snap, thread, frame);

static boolean traceIsSleigh(Trace trace) {
    return trace.getBaseLanguage() instanceof SleighLanguage;
}

try {
    return TraceSleighUtils.evaluateBytes(exprText, trace, snap, thread, frame);
} catch (IllegalArgumentException e) {
    if (e.getMessage().contains("sleigh-based language")) {
        // language is non-Sleigh; compute the value via direct register/memory reads instead
    } else throw e;
}

When it happens

Trigger: Calling the String-expr evaluateBytes overload on a trace whose base language is not a SleighLanguage.

Common situations: Trace opened with a custom/non-Sleigh language provider. A trace recorded against an architecture Ghidra models without a Sleigh front-end. Programmatic traces built with a stub Language.

Related errors

• This expression can only be evaulated on traces with languag
• Sleigh language required
• Emulation requires a Sleigh language
• TracePlatform must use a Sleigh language
• Current trace does not use Sleigh

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/acb0d8f05d978011. Report an issue: GitHub.