Debugging a "weird SIGSEGV" core dump with Codex and GDB inside Docker(medium.com)
medium.com
Debugging a "weird SIGSEGV" core dump with Codex and GDB inside Docker
https://medium.com/@haohang.shi/codex-in-docker-debugging-from-a-weird-sigsegv-core-dump-to-a-real-fix-segv-pkuerr-in-v8-5bf29565f6d0
We hit a SIGSEGV where the backtrace was misleading: our fatal handler tried to print a stack trace and that trace capture sometimes crashed inside libunwind, so it looked like “unwinding is broken”.
What worked was building a deterministic postmortem harness (core dump + debug binary + symbols + matching source paths) inside Docker, then installing Codex in the same container so it could run GDB + rebuild/iterate in-place.
OpenAI Codex pivoted away from unstable backtraces and classified the crash via siginfo_t/ucontext_t. It turned out to be SEGV_PKUERR (Intel MPK/PKU) caused by a thread-local PKRU mismatch when some worker threads entered V8.
PR with the patch: https://github.com/timeplus-io/proton/pull/1091