按建议，继续完成后续工作

结论：将 GET_EXTERNAL_FEED_RATE 接入 canonical feed 状态，并用 G20/G21 长度单位 fixture 验证回读。

wasm-port/docs/compatibility-validation.md

@@ -54,7 +54,7 @@ The validation fails if:
 | `linuxcnc_interp_state_probe` | Validates interpreter state constants and structs compile under the standalone boundary. |
 | `linuxcnc_emc_status_probe` | Validates the standalone `emcStatus` machine-units status boundary used by vendored interpreter conversion and initialization code. |
 | `linuxcnc_namedparam_harness` | Validates LinuxCNC named parameter behavior, `_ini[...]`, and `_hal[...]` adapter resolution. |
-| `linuxcnc_interp_minimal_harness` | Runs G-code fixtures through vendored LinuxCNC parser/execution/conversion code and captures canonical events. |
+| `linuxcnc_interp_minimal_harness` | Runs G-code fixtures through vendored LinuxCNC parser/execution/conversion code, captures canonical events, and validates feed-rate state readback across length-unit changes. |
 | `linuxcnc_parameter_file_harness` | Validates LinuxCNC parameter file restore/save behavior and required/read-only parameter handling. |
 | `linuxcnc_interp_init_harness` | Validates vendored LinuxCNC `Interp::init()` emits canonical initialization boundaries, reads metric/inch machine units, and synchronizes current/selected tool slots through standalone status adapters. |
 | `linuxcnc_indexer_harness` | Validates vendored LinuxCNC single-axis rotary indexer dispatch emits lock/unlock and motion boundaries through the standalone event sink. |
@@ -123,7 +123,8 @@ machine-session validation remain future work.
 
 The current fixture expectations validate standalone behavior against both the
 vendored LinuxCNC source path and an upstream `rs274` side-by-side baseline for
-parser/conversion, arc geometry, offsets, feed-control, comment/logging,
+parser/conversion, arc geometry, offsets, feed-control and feed-state
+readback, comment/logging,
 numbered-parameter, probing, spindle-orient, file-open reset, file-finish,
 tool-reload, tool select/change/length-offset, canned-cycle, state-tag motion,
 tool-table setup, and O-word subroutine fixtures, plus threading/rigid tap,

wasm-port/docs/drift-report.md

@@ -26,6 +26,7 @@ semantic rewrites:
 | 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. |
+| 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 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` guards 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. |

wasm-port/docs/source-reuse-map.md

@@ -43,7 +43,7 @@ Current validation is intentionally mechanical:
 | Ruckig C planner support | Selected `src/emc/tp/cruckig/*.c` and `*.h` files in the manifest | Copy unchanged | Used as LinuxCNC planner support code through vendored TP sources | Vendor byte sync, per-file source probes |
 | Posemath | `src/libnml/posemath/posemath.cc`, `_posemath.c`, `gomath.c`, `sincos.c`, and matching headers | Copy unchanged | `gomath.c` is compiled as C; `rtapi.h` shim is C/C++ compatible for this boundary | Vendor byte sync, per-file source probes, TP probe |
 | RS274 interpreter state and parser | `src/emc/rs274ngc/modal_state.*`, `interp_internal.*`, `interp_read.cc`, `interp_check.cc`, `interp_execute.cc`, `interp_find.cc`, `interp_array.cc`, `interp_queue.*`, `rs274ngc*`, `units.h` | Copy unchanged | Python/remap/runtime edges are isolated in standalone wrappers and shims; parser and execution logic remain LinuxCNC source | Vendor byte sync, per-file source probes, interpreter harness fixtures |
-| RS274 conversion semantics | `src/emc/rs274ngc/interp_convert.cc`, `interp_arc.cc`, `interp_inverse.cc`, `interp_cycles.cc`, `interp_g7x.cc`, `interp_o_word.cc`, `interp_write.cc` | Copy unchanged | Canonical calls are captured by standalone event sink functions; conversion behavior stays in vendored LinuxCNC files | Vendor byte sync, per-file source probes, canonical fixture suite, no standalone `Interp::convert_g()` guard |
+| RS274 conversion semantics | `src/emc/rs274ngc/interp_convert.cc`, `interp_arc.cc`, `interp_inverse.cc`, `interp_cycles.cc`, `interp_g7x.cc`, `interp_o_word.cc`, `interp_write.cc` | Copy unchanged | Canonical calls are captured by standalone event sink functions; conversion behavior stays in vendored LinuxCNC files; feed-rate state is read back through the canonical runtime boundary during length-unit conversion | Vendor byte sync, per-file source probes, canonical fixture suite, no standalone `Interp::convert_g()` guard |
 | Named parameters and tool slot status | `src/emc/rs274ngc/interp_namedparams.cc`, related interpreter headers | Copy unchanged | `_ini[...]` and `_hal[...]` resolve through standalone INI/HAL adapters while lookup order stays LinuxCNC-derived; current/selected tool slot reads for vendored `Interp::synch()` come from the standalone tool adapter | Vendor byte sync, source probe, `linuxcnc_namedparam_harness`, `linuxcnc_interp_init_harness` |
 | Dynamic interpreter base | `src/emc/rs274ngc/interp_base.*` | Copy unchanged | `interp_base.cc` source probe uses standalone `EMC2_HOME` compile-time path boundary for LinuxCNC dynamic interpreter lookup | Vendor byte sync, `linuxcnc_interp_base_source_probe` |
 

wasm-port/runtime/core/linuxcnc_wrap/linuxcnc_interp_minimal_runtime.cpp

@@ -18,6 +18,7 @@
 namespace standalone {
 
 static std::vector<std::string> g_canon_events;
+static double g_external_feed_rate = 0.0;
 
 void reset_canon_events()
 {
@@ -447,7 +448,7 @@ void CANON_ERROR(const char *fmt, ...)
     va_end(ap);
 }
 
-double GET_EXTERNAL_FEED_RATE() { return 0.0; }
+double GET_EXTERNAL_FEED_RATE() { return standalone::g_external_feed_rate; }
 int GET_EXTERNAL_FLOOD() { return 0; }
 CANON_UNITS GET_EXTERNAL_LENGTH_UNIT_TYPE()
 {
@@ -639,6 +640,7 @@ void ARC_FEED(int lineno,
 
 void SET_FEED_RATE(double rate)
 {
+    standalone::g_external_feed_rate = rate;
     std::ostringstream oss;
     oss << "SET_FEED_RATE rate=" << rate;
     standalone::push_canon_event(oss.str());

wasm-port/tests/fixtures/canon/length_units.events

@@ -4,5 +4,6 @@ canon_event=USE_LENGTH_UNITS units=1
 canon_event=SET_FEED_RATE rate=60
 canon_event=STRAIGHT_FEED line=3 x=1.5 y=0 z=0 a=0 b=0 c=0 u=0 v=0 w=0
 canon_event=USE_LENGTH_UNITS units=2
+canon_event=MESSAGE:  feed after_g21=60.0000
 canon_event=SET_FEED_RATE rate=120
-canon_event=STRAIGHT_FEED line=5 x=50.8 y=0 z=0 a=0 b=0 c=0 u=0 v=0 w=0
+canon_event=STRAIGHT_FEED line=6 x=50.8 y=0 z=0 a=0 b=0 c=0 u=0 v=0 w=0

wasm-port/tests/fixtures/gcode/length_units.ngc

@@ -2,4 +2,5 @@ G90 G17 G0 X25.4 Y0 Z0
 G20
 G1 X1.5 F60
 G21
+(DEBUG, feed after_g21=%f#<_feed>)
 G1 X50.8 F120