What causes "{object} is not {err_msg}" in NationalSecurityAgency/ghidra?

Pass a TraceObject whose path matches the process pattern, e.g. 'Processes[1]'.

NationalSecurityAgency/ghidra · error · TypeError

{object} is not {err_msg}

Error message

{object} is not {err_msg}

What it means

Thrown as a TypeError by find_proc_by_pattern in the drgn agent when a TraceObject's path does not match the PROCESS_PATTERN regex. This function extracts a process number from the object's canonical path string; a non-matching path means the object is not a valid process reference.

Source

Thrown at Ghidra/Debug/Debugger-agent-drgn/src/main/py/src/ghidradrgn/methods.py:116

class Thread(TraceObject):
    pass


class ThreadContainer(TraceObject):
    pass


def find_proc_by_num(id: int) -> int:
    if id != util.selected_process():
        util.select_process(id)
    return util.selected_process()


def find_proc_by_pattern(object: TraceObject, pattern: re.Pattern,
                         err_msg: str) -> int:
    mat = pattern.fullmatch(object.path)
    if mat is None:
        raise TypeError(f"{object} is not {err_msg}")
    procnum = int(mat['procnum'])
    return find_proc_by_num(procnum)


def find_proc_by_obj(object: TraceObject) -> int:
    return find_proc_by_pattern(object, PROCESS_PATTERN, "an Process")


def find_proc_by_env_obj(object: TraceObject) -> int:
    return find_proc_by_pattern(object, ENV_PATTERN, "an Environment")


def find_proc_by_threads_obj(object: TraceObject) -> int:
    return find_proc_by_pattern(object, THREADS_PATTERN, "a ThreadContainer")


def find_proc_by_mem_obj(object: TraceObject) -> int:
    return find_proc_by_pattern(object, MEMORY_PATTERN, "a Memory")

View on GitHub (pinned to d5f144c24d)

Solutions

Pass a TraceObject whose path matches the process pattern, e.g. 'Processes[1]'.
Verify the object type before calling — use find_proc_by_obj which delegates to this function.
Check that the path string has the exact format 'Processes[<procnum>]'.

Defensive patterns

Strategy: validation

Validate before calling

import re
# PROCESS_PATTERN must match the one defined in methods.py
PROCESS_PATTERN_TEST = re.compile(r'Processes\[(?P<procnum>\d+)\]')

def is_process_path(path: str) -> bool:
    return PROCESS_PATTERN_TEST.fullmatch(path) is not None

Type guard

def is_process_object(obj: TraceObject) -> bool:
    return PROCESS_PATTERN_TEST.fullmatch(obj.path) is not None

Try / catch

try:
    find_proc_by_obj(obj)
except TypeError as e:
    print(f'Object path does not match process pattern: {obj.path}')
    raise

Prevention

Verify the TraceObject path matches 'Processes[<n>]' before calling process methods.
Use the correct find_*_by_obj function for each object type.
Check obj.path format in the Ghidra UI before passing to the API.

When it happens

Trigger: Passing a TraceObject whose path does not conform to the process path schema (e.g. a thread path like 'Processes[1].Threads[2]' when a process path like 'Processes[1]' is expected). The regex fullmatch fails and TypeError is raised.

Common situations: Calling a method that expects a process object with a thread, frame, or module object instead; path string was manually constructed incorrectly; the Ghidra UI passed the wrong object type to a drgn method.

Related errors

AI-assisted analysis of NationalSecurityAgency/ghidra@d5f144c24d (2026-08-14). Data as JSON: /api/errors/6936c5f841348fce. Report an issue: GitHub.