NationalSecurityAgency/ghidra · warning · ValueError

Offset cannot be a negative value.

Error message

Offset cannot be a negative value.

What it means

Raised by LocateMemoryAddressesForFileOffset.py getFileOffset (Jython) when the hex string parses but the resulting long is negative. Python's long(s, 16) accepts a leading '-', so '-1f' becomes -31 and fails the `myFileOffset < 0` check. This mirrors the Java sibling's negative-offset guard.

Source

Thrown at Ghidra/Features/Base/ghidra_scripts/LocateMemoryAddressesForFileOffset.py:39

# @category Examples   
# @runtime Jython

import sys
from ghidra.program.model.address import Address
from ghidra.program.model.listing import CodeUnit
from ghidra.program.model.listing import Listing
from ghidra.program.model.mem import Memory
from java.util import Set

def getFileOffset():
  userFileOffset = askString('File offset', 'Please provide a hexadecimal file offset')
  try:
    int(userFileOffset,16)
  except ValueError:
     raise ValueError('Please provide a hexadecimal file offset.')
  myFileOffset = long(userFileOffset,16) #specify base 16 since we expect address in hex
  if myFileOffset < 0:
    raise ValueError('Offset cannot be a negative value.')
  return myFileOffset

def processAddress(addr, memBlockName, fileOffset):
  println('File offset ' + hex(fileOffset) + ' is associated with memory block:address ' + memBlockName + ':' + addr.toString());
  myCodeUnit = currentProgram.getListing().getCodeUnitContaining(addr)
  comment = myCodeUnit.getComment(0)
  if not comment:
    myCodeUnit.setComment(0, getScriptName() + ': File offset: ' + hex(fileOffset) + 
      ', Memory block:address ' + memBlockName + ':'+ addr.toString())
  else:
    myCodeUnit.setComment(0, comment + ' ' + getScriptName() + ': File offset: ' + hex(fileOffset) + 
      ', Memory block:address ' + memBlockName + ':' + addr.toString())

myFileOffset = getFileOffset()
mem = currentProgram.getMemory()
addressList = mem.locateAddressesForFileOffset(myFileOffset)
if addressList.isEmpty():
  println('No memory address found for: ' + hex(myFileOffset))

View on GitHub (pinned to d5f144c24d)

Solutions

1. Enter the offset as a positive hex string with no leading '-'.
2. Pre-strip a leading '-' from the input and re-prompt.
3. For high 64-bit offsets, treat the value as unsigned.

Example fix

# before
myFileOffset = long(userFileOffset,16)
if myFileOffset < 0:
    raise ValueError('Offset cannot be a negative value.')

# after
if userFileOffset.startswith('-'):
    raise ValueError('Offset cannot be negative: ' + userFileOffset)
myFileOffset = long(userFileOffset, 16)

s = userFileOffset.strip()
if s.startswith('-'):
    raise ValueError('Offset cannot be negative: ' + s)
myFileOffset = long(s, 16)

def is_non_negative_hex(s):
    return bool(s) and not s.startswith('-') and all(c in '0123456789abcdefABCDEF' for c in s)

try:
    off = getFileOffset()
except ValueError as e:
    if 'negative' in str(e):
        # strip '-' and retry, or re-prompt
        pass
    else:
        raise

When it happens

Trigger: User enters a hex string beginning with '-' (e.g. '-10'). long('-10', 16) returns -16, which is < 0, raising ValueError.

Common situations: Negative offset typed in the prompt. Copy/paste with stray minus. Confusion about signedness of 64-bit offsets.

Related errors

• Please provide a hexadecimal file offset.
• Offset cannot be a negative value.
• Could not get MD5 on file:
• Cannot write to watch variable without an address
• Address does not belong to a memory in the trace

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/7e6ec2582a4d4cb7. Report an issue: GitHub.