bpo-31626: Fix _PyMem_DebugRawRealloc() on OpenBSD by vstinner · Pull Request #4119 · python/cpython

the-knights-who-say-ni

Fix memory debug hooks on OpenBSD: fix _PyMem_DebugRawRealloc().
Previously, the old resized memory block was modified after realloc()
success to fill now unused bytes with the DEADBYTE pattern. On
OpenBSD, modifying the old memory block causes a fatal error.

On OpenBSD, the function now erases the bytes *before* calling
realloc(), but keep a copy of erased bytes to restore them if
realloc() fails.

The behaviour on other platforms is unchanged: erased bytes *after*
realloc() success.

Co-Authored-By: Serhiy Storchaka <storchaka@gmail.com>