GeezerVison is showing github.com — Check exported buffers after the default callback returns by AbhinavMir · Pull Request #735 · msgpack/msgpack-python
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AbhinavMir
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Aug 30, 2026
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The default callback can export the internal buffer with getbuffer().
The packer then continues and can reallocate that buffer.
The export points at freed memory after the reallocation.
Call _check_exports() after the callback returns. The packer now
raises BufferError. The pure Python packer already raises BufferError
in this case.
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🟡 Changes recommended
Other supported user-code hooks can still export the buffer before a reallocating write.
Once you've addressed the issues Copilot identified, you can request another Copilot review.
Pull request overview
Prevents buffer invalidation after default exports the packer’s internal buffer.
Changes:
- Checks active exports after
default returns.
- Adds regression coverage for the unsafe reallocation scenario.
File summaries
| File |
Description |
msgpack/_packer.pyx |
Adds post-callback export validation. |
test/test_buffer.py |
Tests exported-buffer safety during callbacks. |
Review details
- Files reviewed: 2/2 changed files
- Comments generated: 1
- Review effort level: Balanced
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# The callback may have exported the internal buffer.
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# Packing on would reallocate it and invalidate the export.
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self._check_exports()
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