Fixed bug in traceback code.

luprex/core/cpp/traceback.cpp

@@ -1,3 +1,4 @@
+#include <cstring>
 #include "traceback.hpp"
 
 #define TRACEBACK_LEVELS1 12
@@ -26,6 +27,7 @@ int traceback_coroutine(lua_State *L) {
     // Append the traceback.
     lua_Debug ar;
     int firstpart = 1;
+    bool any = false;
     for (int level = 0; lua_getstack(L, level, &ar); level++) {
         if (level > TRACEBACK_LEVELS1 && firstpart) {
             /* no more than `LEVELS2' more levels? */
@@ -40,10 +42,11 @@ int traceback_coroutine(lua_State *L) {
             continue;
         }
         lua_getinfo(L, "Snl", &ar);
-        if ((level == 0) && (*ar.what == 'C') && (std::string(ar.name) == "__newindex")) {
-            continue;
+        if ((!any) && (*ar.what == 'C') && (ar.name != 0)) {
+            if (strcmp(ar.name, "__newindex") == 0) continue;
         }
         if ((ar.currentline > 0) || (*ar.namewhat != 0) || (*ar.what != 'C')) {
+            any = true;
             lua_pushliteral(L, "\n\t");
             lua_pushfstring(L, "%s:", ar.short_src);
             if (ar.currentline > 0)