#284 · zig-utils/zig-js

Parent: #265 Depends on: #262 Roadmap: #142, #134

Define the exact pinned WebAssembly threads instruction surface and implement its binary and validator foundation.

Acceptance:

Check in the exact 0xfe atomic opcode/immediate inventory from the pinned proposal revision.
Decode every selected atomic instruction and fence immediate with deterministic malformed-binary diagnostics.
Validate stack signatures, memory presence, exact natural alignment, and feature gates; keep fence valid without memory.
Accept atomic access and notify on ordinary memories, leave the specified wait-on-unshared trap to runtime issue #286, and reject shared limits without a maximum.
Add focused decoder/validator tests and registry drift checks.

Completed the pinned binary and validator foundation.

98911c4 checks in the exact 67-opcode 0xfe inventory from WebAssembly/threads@979d0fc, including the 13-file corpus count, reserved 0x04–0x0f gap, immediates, alignments, and stack shapes. The registry verifier proves exact source/enum agreement.
040d0c0 decodes shared limits and every atomic/fence immediate, requires maximum on shared memory, enforces exact natural alignment and all operand/result signatures, retains fence-without-memory validity, and distinguishes the runtime-only wait-on-unshared trap.
867aed0 publishes the current boundary and child sequence in README/docs. Execution deliberately traps rather than exposing partial semantics until #285/#286 land.

Verification:

The next dependency is #285 stable shared backing and JavaScript API ownership.