Safety

picop wraps CPython C-API helpers for known-type hot paths. Some APIs skip checks that Python builtins always do. Misuse can crash the process or worse — treat them as trusted-caller tools, not as hardening against hostile input.

Unchecked accessors (OOB is UB)

Helpers like list_get, str_char_at, and siblings assume the index (or shape) is already valid. Out-of-bounds access is undefined behavior.

Prefer:

• list_get_checked / list_get_ref when the index may be OOB

• Bounds you own in Cython (0 <= i < list_len(xs)) before calling unchecked getters

Borrowed pointers

C-string / UTF-8 borrow helpers (uutf8, bas_string, bytes_as_string, …) return pointers that must not outlive the owning Python object. Do not store them past the lifetime of s / b, and do not free them.

Prefer owning APIs when you need a durable value (e.g. uutf8_bytes).

marshal_loads

Untrusted data is unsafe — same class as stdlib marshal.loads. Only deserialize marshal payloads from a trusted source.

*_cstr wants bytes, not str

C-string helpers (map_getitem_cstr, …) take bytes (ASCII/UTF-8), not Python str. Passing str is a type error / footgun.

Runnable demo in the repository: examples/py_cstr_bytes.py.

Reporting vulnerabilities

See the repository SECURITY.md.