cnc_wams/wasm-port/docs/drift-report.md

Drift Report

Current Status

As of the current upstream baseline, no byte-level drift is allowed between files listed in tools/source-manifest.txt and the matching files under ../linuxcnc/.

The enforced upstream baseline is:

60597ee0718873d2449058c824262a275e5e4bad

tools/verify_vendor_sync.sh enforces this by comparing every manifest file against upstream during native validation.

Allowed Standalone Boundaries

The following differences are intentional runtime boundaries, not LinuxCNC semantic rewrites:

Boundary	Standalone treatment
RTAPI	Minimal compatibility shim in runtime/core/shims/rtapi.h.
HAL lookup	Standalone HAL adapter for _hal[...] named parameter reads.
INI lookup	Standalone INI adapter around vendored LinuxCNC INI parser behavior, including boolean conversion through LinuxCNC iniFindBool() and string lookup for INI-declared [RS274NGC]PARAMETER_FILE and [EMCIO]TOOL_TABLE machine file names.
Canonical output	Canonical calls are captured as test events instead of driving hardware.
Feed-rate state	SET_FEED_RATE updates standalone canonical runtime state so vendored convert_length_units() can read it back through GET_EXTERNAL_FEED_RATE() during G20/G21 changes.
Tool-data reload	LinuxCNC RELOAD_TOOLDATA is captured as a canonical test event; browser/native tool-table reload plumbing remains a future host/runtime adapter.
Tool table storage	Vendored LinuxCNC tooldata_common.cc owns tool-table parsing and formatting; the standalone boundary only supplies the in-memory tooldata_get()/tooldata_put() callbacks, exposes load/save through the WASM C ABI, and forwards the host random-toolchanger flag to LinuxCNC tooldata_init().
Tool slot status	Standalone tool adapter state supplies GET_EXTERNAL_TOOL_SLOT() and GET_EXTERNAL_SELECTED_TOOL_SLOT() for vendored Interp::synch(); linuxcnc_interp_init_harness plus Node WASM and browser interpreter smokes guard current/selected slot synchronization.
Interpreter state tags	LinuxCNC UPDATE_TAG callbacks are captured from the state tags packed by vendored interpreter code; standalone code does not derive modal state.
Rotary indexer lock state	LinuxCNC UNLOCK_ROTARY and LOCK_ROTARY callbacks are captured from the vendored single-axis indexer path; standalone code does not implement rotary-indexing semantics.
File flush	LinuxCNC FINISH is captured as a canonical test event on the vendored %-delimited file-reading path.
WASM parameter-file backup	LinuxCNC save_parameters() calls link() to create the .bak parameter-file backup; runtime/core/linuxcnc_wrap/linuxcnc_wasm_posix_stubs.cpp maps that WASM/MEMFS edge to a file copy so the vendored save path can run unchanged.
Interpreter reset	LinuxCNC ON_RESET is captured as a canonical test event on the vendored interpreter reset/file-open path.
Interpreter init	LinuxCNC INIT_CANON and the canonical initialization sequence from vendored Interp::init() are captured as test events in native, Node WASM, and browser interpreter validation.
Comment logging	LinuxCNC LOGOPEN, LOG, LOGAPPEND, and LOGCLOSE callbacks are captured as canonical test events instead of writing host log files.
EMC status machine units	A narrow standalone emcStatus shim exposes the machine-units field used by vendored interpreter conversion and initialization code; linuxcnc_emc_status_probe, linuxcnc_interp_init_harness, and the interpreter WASM/browser init probe guard the inch/mm boundary.
Python/remap	Python/remap hooks are stubbed at the runtime edge.
Dynamic interpreter path	interp_base.cc probe uses standalone EMC2_HOME compile-time path boundary.
Realtime scheduler	TP probes seed deterministic status/config data instead of running LinuxCNC realtime process topology.
Kinematics component lifecycle	Kinematics modules are initialized through LinuxCNC module entry points where native runtime probes exist, while HAL component init/ready/exit, HAL pin allocation, and RTAPI module metadata are handled by standalone shims.
Go math C/C++ linkage	genserkins runtime probing compiles vendored gomath.c through a narrow C++ wrapper so LinuxCNC genserfuncs.c can link to the upstream Go math symbols without editing vendored source.
Switchkins iterative forward	genhexkins runtime probing follows LinuxCNC switchkins iterative-forward behavior, including the first-call warmup path before asserting roundtrip convergence.
Browser storage	OPFS remains outside the native core; runtime/opfs/file-service.js owns browser text-file persistence, runtime/opfs/path-model.js owns host-side storage paths for INI, tool table, parameter, G-code, preview-cache, and session-snapshot content, runtime/opfs/snapshot-store.js owns generic JSON session snapshot persistence, runtime/opfs/machine-file-store.js owns pure-text machine-file and G-code persistence, runtime/opfs/linuxcnc-parameter-bridge.js only copies parameter files between OPFS text storage and the LinuxCNC-backed WASM parameter-file ABI, runtime/opfs/linuxcnc-tool-table-bridge.js only copies tool tables between OPFS text storage and the LinuxCNC-backed WASM tool-table ABI, and runtime/opfs/linuxcnc-machine-session-bridge.js groups INI, parameter, and tool-table loading while using the LinuxCNC-backed INI SDK for [EMCIO]RANDOM_TOOLCHANGER, [RS274NGC]PARAMETER_FILE, and [EMCIO]TOOL_TABLE when available; explicit host session file-name options take precedence over INI-derived file names, missing INI file-name values fall back to host default parameter/tool-table paths, and path validation remains owned by the OPFS path model, including rejection of traversal or nested path segments from INI-derived file names.

Enforced Non-Drift Rules

• Do not edit ../linuxcnc/.
• Do not patch vendored files without adding a patch under patches/ and documenting the reason.
• Do not add standalone Interp::... member definitions outside the documented Python/remap runtime-edge stubs.
• Do not add .c or .cc manifest files without a source compile probe.
• Do not sync from a different upstream commit without updating tools/upstream-baseline.txt and docs/scope-and-baseline.md.

Known Gaps

• No browser/full-core WASM parity tests yet. The INI parser now has Node and Chromium smoke harnesses against vendored LinuxCNC inifile.cc.
• JS SDK validation now covers the INI WASM wrapper around vendored LinuxCNC inifile.cc, including LinuxCNC boolean conversion and INI-declared parameter/tool-table file-name lookup, and the interpreter-core SDK wrapper around the existing exported C ABI. The interpreter SDK only manages strings, Emscripten file writes, and calls into vendored LinuxCNC execution paths, including parameter-file restore/save and tool-table load/save.
• OPFS validation covers a Node mock of the file-service adapter, the host-side path model, generic session snapshot storage, pure-text machine file and G-code storage, parameter/tool-table bridge copying into the interpreter SDK filesystem, grouped machine-session loading, explicit session file-name overrides, default host path fallback when INI file names are absent, invalid INI-derived machine file names, generic session snapshot custom filenames plus envelope/path rejection paths, G-code program filename rejection paths, and a Chromium localhost round trip for those persistence paths.
• Host-side smoke validation is aggregated by tests/host/verify_host_smokes.sh so Node, WASM, OPFS, and browser checks run from one command.
• Identity/trivial, 5axiskins, TRT xyzac/xyzbc, delta, SCARA, PUMA, serial, hexapod, pentapod, and related kinematics sources now have native source-probe coverage.
• Full machine baselines beyond the current identity/trivial, 5axiskins, TRT, delta, SCARA, PUMA, serial genserkins, hexapod genhexkins, pentapod pentakins, and other existing runtime probes are not established.
• Positive cutter-compensated motion and cutter compensation rejection paths now have standalone interpreter fixture coverage through vendored LinuxCNC source.
• Fixture expectations are checked against the standalone vendored source path. The upstream rs274 side-by-side baseline now covers simple motion, arc geometry, offsets, feed-control, comment/logging, numbered-parameter, probing, spindle-orient, file-open reset, file-finish, tool-reload, and tool select/change/length-offset, canned-cycle, state-tag motion, tool-table setup, and O-word subroutine fixtures; it also covers threading/rigid tap, NURBS dispatch boundaries, and comparable canonical runtime edge and program-end cleanup calls. Adapter-heavy fixtures, standalone modal-state assertions, and upstream rs274 output gaps such as WAIT or hidden NURBS control-point detail still need dedicated native LinuxCNC baselines.
• canned_cycles is now in the upstream rs274 side-by-side baseline after the minimal interpreter harness was aligned with LinuxCNC Interp::init() default G73/G83 peck-clearance values for millimeter units.
• tool_table_setup is now in the upstream rs274 side-by-side baseline using a dedicated rs274 -t tool table and -i millimeter-unit INI boundary.
• tool_semantics now compares its T/M6/G43/G49 canonical subset with upstream rs274 -t -i; M61 current-pocket host-state behavior remains a standalone fixture expectation.

Current Drift Conclusion

Within the native extracted-core scope, the port currently has no permitted byte-level drift from vendored LinuxCNC source files. All current behavior coverage is guarded by upstream baseline validation, vendor sync validation, source compile probes, native harnesses, and fixture checks.