ci(spec-drift-guard): extend to Zig + C — three-backend byte-identity enforcement#38
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Post t27#1337 (ExprCast lowered for Zig and C emitters), specs/wire.t27 can now round-trip through three text backends. This PR commits the generated files and extends spec-drift-guard.yml to enforce byte-identity on all of them. Backends now under drift-guard: - Rust: gen/rust/wire.rs (via t27c gen-rust) — from #35 - Zig: gen/zig/wire.zig (via t27c gen) — new - C: gen/c/wire.c (via t27c gen-c) — new Verified locally with t27c built from t27@3c912d9 (post-#1337 master): - diff -u vs regenerated output on all three: empty. - Zig cast form: @as(u8, @intcast((w >> 24) & 255)) etc. - C cast form: ((uint8_t)(((w >> 24) & 255))) etc. - 0 occurrences of 'unsupported: ExprCast' in Zig or C output. - cargo test --lib: 101 passed / 0 failed. Docs refresh: - docs/T27_FIRST_MIGRATION.md: ExprCast section marked resolved on all four backends (Rust #1320, Zig+C #1337, Verilog pre-#1320). Build section notes drift-guard covers all three text backends. - docs/T27_PORT_STATUS.md: wire.rs row now says 'T27-FIRST (full, multi-target)' and lists all three gen files. Option B closed end-to-end: upstream ExprCast in all four emitters, tri-net multi-target drift-guard live, parse-path delegates to auto-gen u32_be (#37). Anchor: phi^2 + phi^-2 = 3.
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…dit-trail primitive Bounded expansion (not full v1). The skeleton previously proposed the auditability primitive abstractly (Sections 1-4); this commit adds Section 5 reporting that the primitive is now empirically realized end-to-end at tri-net main dc1bebb + t27 master 3c912d9. Section 5 subsections: - 5.1 What is materialized -- one spec (specs/wire.t27), three generated backends (gen/{rust,zig,c}/wire.*), one workflow (spec-drift-guard.yml), consumer path under the same umbrella (src/wire.rs -> u32_be). - 5.2 Audit-trail tuple (concrete instance) -- (tri-net@dc1bebb, t27@3c912d9, spec-drift-guard run) is the minimal fetch set for a third party to independently verify byte-identity. - 5.3 Merge chain table -- 5 tri-net PRs (#33/#34/#35/#37/#38) + 2 t27 PRs (#1320/#1337) with merge SHAs. - 5.4 Empirical checks at HEAD -- three diff -u results (all empty), zero 'unsupported: ExprCast' in Zig/C output, 101 lib tests green including header_roundtrips as empirical byte-order-equivalence proof. - 5.5 What this reference impl does NOT show -- byte-identity is not functional correctness; only one spec is covered so far; no silicon; trust in t27c itself is not eliminated (moved, per Carrone 2026). Sync updates across the doc: - Header cross-link: 91a5b63 -> dc1bebb (post-#38). - Section 3.1: describes all three gen targets, not just Rust. - Section 3.2: drift-guard covers Rust + Zig + C; links to #35 + #38. - Section 3.3: ExprCast marked resolved on all four backends (Rust #1320, Zig+C #1337, Verilog pre-#1320). - Section 6 (Limits): removed obsolete 'Rust-only SSOT until #1333' bullet; added trust-surface-of-t27c and no-HDL-target-yet bullets. - Section 7 (Future work): struck through completed Zig+C drift-guard item; added protocol-stack expansion, t27c deterministic-build items. - Appendix A: three-target reproducibility recipe (8 steps), pins tri-net@dc1bebb + t27@3c912d9. Draft only -- not for external circulation. Anchor: phi^2 + phi^-2 = 3.
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…= 9 checks)
Refactored from 6 copy-pasted step pairs (wire-only) into 3 compact
loop-based steps (one per backend: Rust/Zig/C). Each loops over all
specs [wire, hello, etx], regenerates from t27c, diffs against committed.
Scalable: adding the next spec (crc16, byte_utils, ...) = add the name
to the for-loop in each step. No new step needed.
Drift matrix coverage now:
wire.t27 × {Rust, Zig, C} = 3 checks (existing, verified by #38)
hello.t27 × {Rust, Zig, C} = 3 checks (NEW)
etx.t27 × {Rust, Zig, C} = 3 checks (NEW)
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What
Extends
.github/workflows/spec-drift-guard.ymlfrom one backend (Rust) to three (Rust + Zig + C), and commits the newly-generatable output files:gen/zig/wire.zig— viat27c gen(73 lines)gen/c/wire.c— viat27c gen-c(128 lines)gen/rust/wire.rs— unchanged, still under guard from ci(spec-drift-guard): enforce specs/wire.t27 -> gen/rust/wire.rs SSOT byte-for-byte #35Why this is possible now
gHashTag/t27#1337 (merged into t27 master @
3c912d9) loweredExprCastin the Zig and C emitters:@as(<T>, @intCast(<operand>))— narrows and widens (stronger than the@as-only suggestion in t27#1333).((<uintN_t>)(<operand>))viaSelf::type_to_c.Before that,
gen (Zig)silently dropped everyas-cast (_ => {}default arm) andgen-cemitted/* unsupported: ExprCast */. Sincespecs/wire.t27uses(w >> 24) & 255) as u8inbe_byteand fourb as u32shifts inu32_be, neither backend could produce compilable output until #1337.Local verification (t27c from t27@3c912d9)
t27c gen-rust specs/wire.t27 | diff -u gen/rust/wire.rs -→ emptyt27c gen specs/wire.t27 | diff -u gen/zig/wire.zig -→ emptyt27c gen-c specs/wire.t27 | diff -u gen/c/wire.c -→ emptygrep -c 'unsupported: ExprCast' gen/zig/wire.zig gen/c/wire.c→ 0 / 0cargo test --lib→ 101 passed / 0 failedreturn @as(u8, @intCast((w >> 24) & 255));return ((uint8_t)(((w >> 24) & 255)));Workflow structure
Three regen + diff step-pairs, each with its own
::error file=…::annotation on drift. Path filter unchanged (specs/**,gen/**,build.rs, workflow itself) — coverage widens becausegen/**now matches three directories.Docs refresh
docs/T27_FIRST_MIGRATION.md: ExprCast section marked resolved on all four backends (Rust #1320, Zig+C #1337, Verilog pre-#1320); build section lists all three text backends under drift-guard.docs/T27_PORT_STATUS.md: wire.rs row upgraded to 'T27-FIRST (full, multi-target)'.Chain context
Closes Option B end-to-end for this loop:
3c912d90e1f1f2Anchor: phi^2 + phi^-2 = 3.