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.
Canonical output	Canonical calls are captured as test events instead of driving hardware.
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	trivkins.c and 5axiskins.c are initialized through LinuxCNC module entry points while HAL component init/ready/exit, HAL pin allocation, and RTAPI module metadata are handled by standalone shims.
Browser storage	OPFS remains outside the native core and is not yet connected.

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::convert_g().
• 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/WASM parity tests yet.
• No JS SDK validation yet.
• No OPFS persistence validation yet.
• Identity/trivial kinematics and LinuxCNC 5axiskins now have native source-probe coverage; TRT xyzac/xyzbc, serial, delta, SCARA, and other machine-specific kinematics are not yet extracted.
• Full machine baselines beyond the current identity/trivial and 5axiskins probes are not established.
• Fixture expectations are currently checked against the standalone vendored source path, not by running a native LinuxCNC binary for every fixture.

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.