提示词：补齐 rtapi_vsnprintf WASM shim

结论：按 LinuxCNC src/rtapi/uspace_common.h 和 src/rtapi/rtapi.h，将 userspace rtapi_vsnprintf 适配为 vsnprintf 包装，并在 WASM runtime probe 覆盖 snprintf、va_list 和截断返回值。

检查：./test-native.sh 通过；./test-linuxcnc-source-link.sh 通过。

core/wasm_shims/cnc_sim_wasm_runtime_probe_main.cc

@@ -4,6 +4,7 @@
 #include "libnml/nml/stat_msg.hh"
 
 #include <cmath>
+#include <cstdarg>
 #include <cstdlib>
 #include <cstring>
 #include <string>
@@ -16,6 +17,8 @@ extern "C" {
 extern PyObject *PyInit_interpreter(void);
 extern PyObject *PyInit_emccanon(void);
 extern struct _inittab builtin_modules[];
+extern int rtapi_snprintf(char *buf, unsigned long size, const char *fmt, ...);
+extern int rtapi_vsnprintf(char *buf, unsigned long size, const char *fmt, va_list ap);
 }
 
 // LinuxCNC source basis: src/emc/rs274ngc/rs274ngc_pre.cc provides read(),
@@ -155,6 +158,34 @@ bool builtin_modules_match_linuxcnc_preview_runtime() {
            builtin_modules[2].initfunc == nullptr;
 }
 
+int call_rtapi_vsnprintf(char *buffer, unsigned long size, const char *format, ...) {
+    va_list args;
+    va_start(args, format);
+    const int result = rtapi_vsnprintf(buffer, size, format, args);
+    va_end(args);
+    return result;
+}
+
+bool rtapi_formatting_matches_linuxcnc_userspace() {
+    // LinuxCNC source basis: src/rtapi/uspace_common.h implements both
+    // rtapi_snprintf() and rtapi_vsnprintf() as userspace vsnprintf() wrappers.
+    char formatted[32]{};
+    if (rtapi_snprintf(formatted, sizeof(formatted), "HAL_%s_%d", "probe", 7) != 11 ||
+        std::strcmp(formatted, "HAL_probe_7") != 0) {
+        return false;
+    }
+
+    char via_va_list[32]{};
+    if (call_rtapi_vsnprintf(via_va_list, sizeof(via_va_list), "%s.%02d", "axis", 3) != 7 ||
+        std::strcmp(via_va_list, "axis.03") != 0) {
+        return false;
+    }
+
+    char truncated[5]{};
+    return rtapi_snprintf(truncated, sizeof(truncated), "abcdef") == 6 &&
+           std::strcmp(truncated, "abcd") == 0;
+}
+
 } // namespace
 
 int main() {
@@ -176,6 +207,9 @@ int main() {
     if (!builtin_modules_match_linuxcnc_preview_runtime()) {
         return 10;
     }
+    if (!rtapi_formatting_matches_linuxcnc_userspace()) {
+        return 11;
+    }
 
     std::vector<CncSimEvent> events;
     CncSimHandle *sim = cnc_sim_create();

core/wasm_shims/rtapi_compat.cc

@@ -2,7 +2,8 @@
 #include <cstdio>
 
 // LinuxCNC source basis: src/rtapi/uspace_common.h provides rtapi_snprintf()
-// for userspace RTAPI formatting; src/rtapi/rtapi.h declares the API.
+// and rtapi_vsnprintf() for userspace RTAPI formatting; src/rtapi/rtapi.h
+// declares both APIs.
 extern "C" int rtapi_snprintf(char *buf, unsigned long size, const char *fmt, ...) {
     va_list ap;
     va_start(ap, fmt);
@@ -10,3 +11,7 @@ extern "C" int rtapi_snprintf(char *buf, unsigned long size, const char *fmt, ..
     va_end(ap);
     return rc;
 }
+
+extern "C" int rtapi_vsnprintf(char *buf, unsigned long size, const char *fmt, va_list ap) {
+    return std::vsnprintf(buf, static_cast<std::size_t>(size), fmt, ap);
+}