NationalSecurityAgency/ghidra · warning · IllegalArgumentException

Offset cannot be a negative value.

Error message

Offset cannot be a negative value.

What it means

Thrown by LocateMemoryAddressesForFileOffset.getFileOffset (Java) when the user-supplied string, parsed as base-16, yields a negative long. Java's Long.parseLong(..., 16) accepts a leading '-' so an input like '-10' parses to -16; the script rejects that. Note: a non-hex string throws NumberFormatfirst and is not caught here.

Source

Thrown at Ghidra/Features/Base/ghidra_scripts/LocateMemoryAddressesForFileOffset.java:66

		}
		//address set size is > 1, file offset matches to multiple addresses.  
		//Let the user decide which address they want.
		else {
			println("Possible memory block:address are:");
			for (Address addr : addressList) {
				println(mem.getBlock(addr).getName() + ":" + addr.toString());
			}
		}
	}

	public long getFileOffset()
			throws CancelledException, NumberFormatException, IllegalArgumentException {
		String userFileOffset =
			askString("File offset", "Please provide a hexadecimal file offset");
		long myFileOffset = 0;
		myFileOffset = Long.parseLong(userFileOffset, 16);
		if (myFileOffset < 0) {
			throw new IllegalArgumentException(
				"Offset cannot be a negative value." + userFileOffset);
		}
		return myFileOffset;
	}

	public void processAddress(Address addr, String memBlockName, long fileOffset) {
		println("File offset " + Long.toHexString(fileOffset) +
			" is associated with memory block:address " + memBlockName + ":" + addr.toString());
		CodeUnit myCodeUnit = currentProgram.getListing().getCodeUnitContaining(addr);
		String comment = myCodeUnit.getComment(CommentType.EOL);
		if (comment == null) {
			myCodeUnit.setComment(CommentType.EOL,
				this.getScriptName() + ": File offset: " + Long.toHexString(fileOffset) +
					", Memory block:address " + memBlockName + ":" + addr.toString());
		}
		else {
			myCodeUnit.setComment(CommentType.EOL,
				comment + ", " + this.getScriptName() + ": File offset: " +

View on GitHub (pinned to d5f144c24d)

Solutions

1. Enter the offset as a positive hexadecimal value without a leading '-'.
2. If you need to express a high 64-bit value whose MSB is set, use Long.parseUnsignedLong or accept it as unsigned.
3. Pre-validate the input string: reject or strip leading '-' before parsing.

Example fix

// before
myFileOffset = Long.parseLong(userFileOffset, 16);
if (myFileOffset < 0) {
    throw new IllegalArgumentException("Offset cannot be a negative value." + userFileOffset);
}

// after - reject leading '-' early and parse unsigned
if (userFileOffset.startsWith("-")) {
    throw new IllegalArgumentException("Offset cannot be negative: " + userFileOffset);
}
long myFileOffset = Long.parseUnsignedLong(userFileOffset, 16);

String s = userFileOffset.trim();
if (s.isEmpty() || s.startsWith("-")) {
    throw new IllegalArgumentException("Offset must be a non-negative hex string.");
}
long v = Long.parseUnsignedLong(s, 16);

static boolean isNonNegativeHex(String s) {
    return s != null && !s.isEmpty() && !s.startsWith("-") && s.matches("[0-9a-fA-F]+");
}

try {
    long off = getFileOffset();
} catch (IllegalArgumentException e) {
    if (e.getMessage().startsWith("Offset cannot be a negative value")) {
        // re-prompt the user
    } else throw e;
}

When it happens

Trigger: Calling getFileOffset after the user enters a hex string with a leading minus sign (e.g. '-1f'). Long.parseLong('-1f', 16) returns -31, which is < 0, triggering the IllegalArgumentException.

Common situations: User types a negative offset in the prompt. Paste/copy error prepending a minus. Confusion between signed and unsigned 64-bit offsets.

Related errors

• Please provide a hexadecimal file offset.
• Offset cannot be a negative value.
• Address string should have at most one colon (:)
• Bad nodeSize: {}
• Invalid number of elements specified: {}

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/c2102b2614efa885. Report an issue: GitHub.