Check exported buffers after the default callback returns - #735
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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.
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Pull request overview
Prevents buffer invalidation after default exports the packer’s internal buffer.
Changes:
- Checks active exports after
defaultreturns. - 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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Comment on lines
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| # The callback may have exported the internal buffer. | ||
| # Packing on would reallocate it and invalidate the export. | ||
| self._check_exports() |
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#733