Lua: add stack traceback when erroring out

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@21048 a1c6a512-1295-4272-9138-f99709370657

apps/plugins/lua/rocklua.c

@@ -46,6 +46,95 @@ static void rocklua_openlibs(lua_State *L) {
   }
 }
 
+/* ldlib.c */
+static lua_State *getthread (lua_State *L, int *arg) {
+  if (lua_isthread(L, 1)) {
+    *arg = 1;
+    return lua_tothread(L, 1);
+  }
+  else {
+    *arg = 0;
+    return L;
+  }
+}
+
+#define LEVELS1 12      /* size of the first part of the stack */
+#define LEVELS2 10      /* size of the second part of the stack */
+
+static int db_errorfb (lua_State *L) {
+  int level;
+  int firstpart = 1;  /* still before eventual `...' */
+  int arg;
+  lua_State *L1 = getthread(L, &arg);
+  lua_Debug ar;
+  if (lua_isnumber(L, arg+2)) {
+    level = (int)lua_tointeger(L, arg+2);
+    lua_pop(L, 1);
+  }
+  else
+    level = (L == L1) ? 1 : 0;  /* level 0 may be this own function */
+  if (lua_gettop(L) == arg)
+    lua_pushliteral(L, "");
+  else if (!lua_isstring(L, arg+1)) return 1;  /* message is not a string */
+  else lua_pushliteral(L, "\n");
+  lua_pushliteral(L, "stack traceback:");
+  while (lua_getstack(L1, level++, &ar)) {
+    if (level > LEVELS1 && firstpart) {
+      /* no more than `LEVELS2' more levels? */
+      if (!lua_getstack(L1, level+LEVELS2, &ar))
+        level--;  /* keep going */
+      else {
+        lua_pushliteral(L, "\n\t...");  /* too many levels */
+        while (lua_getstack(L1, level+LEVELS2, &ar))  /* find last levels */
+          level++;
+      }
+      firstpart = 0;
+      continue;
+    }
+    lua_pushliteral(L, "\n\t");
+    lua_getinfo(L1, "Snl", &ar);
+    lua_pushfstring(L, "%s:", ar.short_src);
+    if (ar.currentline > 0)
+      lua_pushfstring(L, "%d:", ar.currentline);
+    if (*ar.namewhat != '\0')  /* is there a name? */
+        lua_pushfstring(L, " in function " LUA_QS, ar.name);
+    else {
+      if (*ar.what == 'm')  /* main? */
+        lua_pushfstring(L, " in main chunk");
+      else if (*ar.what == 'C' || *ar.what == 't')
+        lua_pushliteral(L, " ?");  /* C function or tail call */
+      else
+        lua_pushfstring(L, " in function <%s:%d>",
+                           ar.short_src, ar.linedefined);
+    }
+    lua_concat(L, lua_gettop(L) - arg);
+  }
+  lua_concat(L, lua_gettop(L) - arg);
+  return 1;
+}
+
+/* lua.c */
+static int traceback (lua_State *L) {
+  lua_pushcfunction(L, db_errorfb);
+  lua_pushvalue(L, 1);  /* pass error message */
+  lua_pushinteger(L, 2);  /* skip this function and traceback */
+  lua_call(L, 2, 1);  /* call debug.traceback */
+  return 1;
+}
+
+static int docall (lua_State *L) {
+  int status;
+  int base = lua_gettop(L);  /* function index */
+  lua_pushcfunction(L, traceback);  /* push traceback function */
+  lua_insert(L, base);  /* put it under chunk and args */
+  status = lua_pcall(L, 0, 0, base);
+  lua_remove(L, base);  /* remove traceback function */
+  /* force a complete garbage collection in case of errors */
+  if (status != 0) lua_gc(L, LUA_GCCOLLECT, 0);
+  return status;
+}
+
+
 /***************** Plugin Entry Point *****************/
 enum plugin_status plugin_start(const void* parameter)
 {
@@ -69,7 +158,7 @@ enum plugin_status plugin_start(const void* parameter)
         status = luaL_loadfile(L, filename);
         if (!status) {
             rb->lcd_clear_display();
-            status = lua_pcall(L, 0, 0, 0);
+            status = docall(L);
         }
 
         dlmalloc_stats();