P1: fix Zig FFI to build and match the Idris2 ABI#37
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The Zig FFI (src/interface/ffi/src/main.zig) failed to compile under Zig 0.14.0 with two errors, both in functions reached from betlangiser_init / sampleDistribution: 1. betlangiser_init: `@bitCast(std.time.nanoTimestamp())` was assigned to the u64 PRNG seed, but nanoTimestamp() returns i128 — a @bitcast size mismatch (128 -> 64 bits). Fixed by reinterpreting the i128 as u128 and truncating to u64: `@truncate(@as(u128, @bitcast(std.time.nanoTimestamp())))`. 2. sampleDistribution (Box-Muller normal sampling): local variables `u1` and `u2` shadowed the built-in primitive type `u1`, which is an error in Zig 0.14. Renamed to `unif1`/`unif2`. Both fixes are local and behaviour-preserving. No exported C symbol names, signatures, or integer encodings changed: all 26 `C:betlangiser_*` symbols in the Idris2 ABI (Foreign.idr) still map to matching `export fn`s, the Result enum (ok=0..sampling_failed=6) still matches Types.idr resultToInt, the TernaryBool encoding (t_false=0, t_true=1, t_unknown=2) matches ternaryToInt, and the DistributionTag encoding (normal=0..custom=4) matches distributionTag. The Idris2 ABI remains the source of truth and was left untouched. Verification: - `zig test src/main.zig -lc` -> all 9 tests pass, zero errors/warnings. - `idris2 --build betlangiser-abi.ipkg` -> exit 0 (build dir removed). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_019xMKB3T4Vo5FYC7Czx3JSH
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Summary
The Zig FFI (
src/interface/ffi/src/main.zig) failed to compile under Zig 0.14.0. This PR fixes the two compile errors with minimal, behaviour-preserving changes. Onlysrc/interface/ffi/src/main.zigis touched; the Idris2 ABI is the source of truth and was left untouched.Errors (from
zig test src/main.zig -lc)src/main.zig:118—@bitCast size mismatch: destination type 'u64' has 64 bits but source type 'i128' has 128 bits. Inbetlangiser_init,std.time.nanoTimestamp()returnsi128, but it was@bitCastdirectly into theu64PRNG seed.src/main.zig:558—name shadows primitive 'u1'. InsampleDistribution(Box-Muller normal sampling), the localsu1/u2shadow the built-in primitive typeu1, which is an error in Zig 0.14.Fixes
i128timestamp asu128, then truncate tou64:@truncate(@as(u128, @bitCast(std.time.nanoTimestamp()))).u1/u2→unif1/unif2.Net diff: 4 insertions, 4 deletions in one file.
ABI fidelity (preserved)
No exported C symbol names, signatures, or integer encodings changed:
C:betlangiser_*symbols inForeign.idrstill map to matchingexport fns.Resultenumok=0 … sampling_failed=6matchesTypes.idrresultToInt.TernaryBoolencodingt_false=0, t_true=1, t_unknown=2matchesternaryToInt.DistributionTagencodingnormal=0 … custom=4matchesdistributionTag.Verification
cd src/interface/ffi && zig test src/main.zig -lc→ all 9 tests pass, zero errors/warnings, exit 0.cd src/interface/abi && idris2 --build betlangiser-abi.ipkg→ exit 0 (build dir removed afterwards).C:<name>inForeign.idrhas a matchingexport fn <name>inmain.zig(26/26 OK).Note: any rust-ci / Hypatia / governance red checks are pre-existing estate-infra issues unrelated to this Zig-only change.
🤖 Generated with Claude Code
https://claude.ai/code/session_019xMKB3T4Vo5FYC7Czx3JSH
Generated by Claude Code