Erlang/OTP source reference

Clause tracks the official maint-29 branch. The reviewed pin lives in references/otp-pin.cmake:

• Revision 21776803ecd11f5fa948732c0ec66b8f325dedfc (upstream commit dated 2026-09-22), last confirmed unchanged on 2026-10-03.
• Installed oracle used for goldens and audits: OTP 29.1.1 / ERTS 17.1.

references/otp is an ignored checkout. Normal builds and tests use project-owned goldens and need neither the checkout nor installed OTP. Configuration and tests never fetch or advance the reference. Live audits are opt-in with -DCLAUSE_OTP_AUDITS=ON; see fixture regeneration.

OTP source, copied helpers and OTP-generated headers never enter Git. Committed test inputs are locally authored; committed goldens are observations of those inputs. See validation.

Refresh procedure

Run at the start of OTP-dependent work.

1. Check git -C references/otp status --short and preserve local work. Fetch: git -C references/otp fetch https://github.com/erlang/otp.git refs/heads/maint-29:refs/remotes/origin/maint-29. Review git -C references/otp log -1 origin/maint-29 and changes since the pin, especially grammar, scanner, preprocessor and corpus inputs.
2. Fast-forward the clean local branch: git merge --ff-only origin/maint-29 (first setup: git switch --create maint-29 --track origin/maint-29). Use LF checkout bytes (core.autocrlf=false) so checksums match on every host; on an existing Windows checkout normalize only manifest-listed text files and erl_parse.yrl, and keep upstream binary fixtures unchanged.
3. Generate the compiler header from the same revision (from the project root): perl references/otp/erts/emulator/utils/beam_makeops -compiler -outdir references/otp/lib/compiler/src references/otp/lib/compiler/src/genop.tab. On Windows normalize only the generated beam_opcodes.hrl to LF.
4. Update the pin and verify every path in tests/fixtures/parser/phase6/otp.tsv. Refresh hashes only after reviewing real upstream changes. If erl_parse.yrl changes, review tests/fixtures/parser/grammar.tsv, its fixtures and phase6/coverage.tsv; every ordinary production needs a measured witness.
5. Configure with CLAUSE_OTP_AUDITS=ON and CLAUSE_OTP_SOURCE_ROOT set to the checkout. Run the audit tests and tests/compiler/patternmatch/regenerate.py --corpus all --check. Record the revision and outcomes below; report drift instead of regenerating to hide it.

Pin history

Historical records keep the revision they were made against.