P1: implement real Zig FFI matching the Idris2 ABI

[hyperpolymath]

What was wrong

The Zig FFI at src/interface/ffi/src/main.zig did not compile. The analysis-engine handle was declared as:

pub const Handle = opaque {
    allocator: std.mem.Allocator,
    initialized: bool,
    ...
};

Zig rejects this with error: opaque types cannot have fields. The file was effectively a half-/unrendered template that never built, so it could not honour the ABI contract defined by the Idris2 ABI (the source of truth).

The fix

main.zig is rewritten as a self-contained, compiling reference FFI driven by src/interface/abi/Atsiser/ABI/Foreign.idr and Types.idr:

• Exact symbols: exports all 20 C:atsiser_* symbols declared in Foreign.idr, verbatim (atsiser_init, atsiser_free, atsiser_parse_header, atsiser_analyse_allocations, atsiser_build_ownership_graph, atsiser_detect_buffers, atsiser_generate_viewtypes, atsiser_generate_proofs, atsiser_generate_bounds_proofs, atsiser_compile_ats2, atsiser_verify_linkage, atsiser_allocation_count, atsiser_ownership_edge_count, atsiser_proof_count, atsiser_analysis_report, atsiser_free_string, atsiser_last_error, atsiser_version, atsiser_build_info, atsiser_is_initialized). All callconv(.C).
• Matching signatures: Bits64 handle ↔ opaque ?*Engine; Idris String arg ↔ ?[*:0]const u8; returns-a-string Bits64 ↔ ?[*:0]const u8; result-returning Bits32 ↔ Result enum as c_int; counts ↔ c_uint.
• Matching result codes: Result = enum(c_int) whose values exactly match Atsiser.ABI.Types.resultToInt — Ok=0, Error=1 (err), InvalidParam=2, OutOfMemory=3, NullPointer=4, OwnershipViolation=5, BoundsViolation=6 (7 codes).
• Memory-sane in-memory reference: a real Engine tracking allocation sites, ownership edges, and buffer/proof counts via std.heap.c_allocator, with proper deinit and C-string ownership (dup / std.mem.span / allocPrintZ / atsiser_free_string). libclang parsing and patsopt (ATS2 → C) bridging remain stubs, but signatures, symbols, and result codes match the ABI.
• Tests: two test blocks — the main analysis pipeline (parse → analyse → ownership graph → proofs → JSON report) and null-handle / invalid-param rejection.

Only src/interface/ffi/ (the Zig) was touched. The Idris ABI, Cargo, and other files are unchanged.

Verification

• cd src/interface/ffi && zig test src/main.zig -lc → all tests pass, zero errors/warnings:

  1/2 main.test.analysis pipeline and report...OK
  2/2 main.test.null handle and invalid params are rejected...OK
  All 2 tests passed.
  

• cd src/interface/abi && idris2 --build atsiser-abi.ipkg → exits 0 clean (builds Types, Layout, Proofs, Foreign), build dir removed afterward.
• Symbol cross-check: every C:<name> in Foreign.idr has a matching export fn <name> in main.zig (20/20, perfect diff match).
• Result codes match resultToInt exactly (7/7).

Note: any rust-ci / Hypatia / governance CI reds are pre-existing estate-infra issues unrelated to this Zig-only change.

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https://claude.ai/code/session_019xMKB3T4Vo5FYC7Czx3JSH

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