GeezerVison is showing github.com — Reject a mode change while an object is incomplete by AbhinavMir · Pull Request #736 · msgpack/msgpack-python
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AbhinavMir
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Aug 30, 2026
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Unpacker.skip() does not build the objects on the parser stack. So
stack[].obj stays uninitialized after an incomplete skip(). A later
Unpacker.unpack() writes an array item through that pointer and the
process crashes. The reverse order drops the reference that the
construct pass took.
Record the mode that started the object in unpack_context.
unpack_construct() and unpack_skip() now raise ValueError on a change.
The parser state stays intact, so the original mode still finishes the
object.
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🟢 Approval recommended
The guard preserves parser state and the tests cover both unsafe mode-switch directions.
Pull request overview
Prevents unsafe switching between Unpacker.unpack() and skip() while parsing an incomplete container.
Changes:
- Tracks the active parser construction mode.
- Rejects incompatible mode switches with
ValueError.
- Adds regression coverage for both switch directions and state recovery.
File summaries
| File |
Description |
msgpack/unpack_template.h |
Adds mode tracking and validation. |
test/test_sequnpack.py |
Tests rejected mode switches and subsequent completion. |
Review details
- Files reviewed: 2/2 changed files
- Comments generated: 0
- Review effort level: Balanced
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