bug: trios-hdc + trios-sacred linker errors — missing Zig FFI symbols on arm64

[gHashTag]

Problem

cargo test --workspace fails with linker errors:

trios-hdc

Undefined symbols for architecture arm64:
  "_hdc_bind"
  "_hdc_random_vector"
  "_hdc_similarity"
  "_hdc_space_create"
  "_hdc_space_destroy"

trios-sacred

Undefined symbols for architecture arm64:
  "_sacred_golden_sequence"
  "_sacred_phi_bottleneck"

Root Cause

These crates link against Zig vendor libraries (zig-hdc, zig-physics) via FFI. The compiled .dylib/.a files are not present because:

1. Zig vendor submodules are not initialized
2. The build.rs scripts warn but don't error: "zig-golden-float vendor not found, skipping Zig build"

Impact

• cargo test --workspace fails at link time for these 2 crates
• All other tests pass individually

Possible Fixes

1. Initialize Zig submodules: git submodule update --init --recursive
2. Build Zig vendors: cd external/zig-hdc && zig build
3. Or gate the test linking behind a feature flag (like trios-training-ffi does)

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Diagnosed by trios-doctor (leukocyte agent)

[gHashTag]

Root cause confirmed

Zig vendor submodules not initialized. build.rs scripts silently skip:

warning: trios-golden-float@0.1.0: zig-golden-float vendor not found, skipping Zig build

Workaround: gate tests behind feature flags (like trios-training-ffi does) so cargo test --workspace passes without Zig libs.

[gHashTag]

Fixed in commit 49555fa

Applied has_zig_lib cfg gate pattern to all 4 Zig FFI crates:

Crate	Pattern	Status
trios-hdc	#[cfg(has_zig_lib)] on extern "C" + stubs	GREEN
trios-sacred	Same	GREEN
trios-golden-float	Same	GREEN
trios-physics	Same	GREEN

build.rs emits cargo:rustc-cfg=has_zig_lib only when Zig .a exists.

Result

cargo test --workspace: 383 passed, 0 failed, 74 test suites
cargo check --workspace: GREEN

When Zig vendors are built, the real FFI is used. Without them, stubs return zeros/errors.

[gHashTag]

🔒 AGENT ECHO CLAIMING: #114 | Branch: fix/zig-ffi-feature-gate | Status: IN PROGRESS

ts: 2026-04-21T03:45:00Z
issue: #114
status: adding feature flags to trios-hdc and trios-sacred to gate zig FFI
next: wrap extern blocks behind #[cfg(feature = "zig-ffi")], add stubs for no-ffi