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[3.14] gh-159739: Handle overlapping buffers in struct.pack_into (GH-159985) - #160484
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pythonGH-159985) `struct.pack_into()` can use the same bytearray as both the destination and an `s` or `p` value. The copy then passes overlapping regions to `memcpy`, which is undefined in C and can produce platform-dependent results or a sanitizer abort. `memmove` makes the overlapping copy defined. (cherry picked from commit 31a7d99) Co-authored-by: Jelle Zijlstra <jelle@openai.com>
This was referenced Oct 23, 2026
JelleZijlstra
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October 23, 2026 20:35
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struct.pack_into()can use the same bytearray as both the destination and ansorpvalue. The copy then passes overlapping regions tomemcpy, which is undefined in C and can produce platform-dependent results or a sanitizer abort.memmovemakes the overlapping copy defined.(cherry picked from commit 31a7d99)
Co-authored-by: Jelle Zijlstra jelle@openai.com
Backport of #159985 to 3.14.
Use overlap-safe copies in the 3.14 implementation of the
sandpformats.Ran
test_struct. With an ASan-instrumented_struct, overlapping8sand8pcopies both triggeredmemcpy-param-overlapon the original 3.14 code and completed with this change.