按推荐建议，继续执行

结论：补齐 interp_base.cc 与 gomath.c 的 vendored LinuxCNC 直接源码编译探针，增加 C 编译边界，并让 rtapi shim 支持 C/C++，继续确保核心功能来源于 LinuxCNC 源程序。

wasm-port/docs/porting-steps-standalone.md

@@ -473,6 +473,12 @@ Current verified progress:
   file under `vendor/linuxcnc/` and the matching file under `../linuxcnc/`.
   `tools/source-manifest.txt` was also de-duplicated so the manifest is a
   single authoritative extraction list.
+- Direct source compile probes now also cover vendored `interp_base.cc` and
+  `gomath.c`. `interp_base.cc` uses a standalone `EMC2_HOME` compile-time
+  path boundary for LinuxCNC's dynamic interpreter lookup, and `gomath.c` is
+  compiled as C with `gcc` so its LinuxCNC C linkage is preserved. The
+  standalone `rtapi.h` shim was made C/C++ compatible for this C-source
+  boundary without changing vendored LinuxCNC files.
 
 ## Phase 4: Port INI Parsing Without Editing Upstream