lua LCD (Lua Compact Debug) patch

LCD developed 9/2015 by Terry Ellison

 We've already discarded the ldebug module from lua
 it only makes sense to discard the debug info as well
 adds 1.5 K to the binary
 saves 8 Kb on the base state
 once scripts start getting called i've seen 10-50Kb savings but it all depends on
 what exactly you are running

Change-Id: Ibb74f344df1c4c96380ec6c98b010a810e9ae9cc

apps/plugins/lua/lbaselib.c

@@ -19,6 +19,13 @@
 #include "lauxlib.h"
 #include "lualib.h"
 
+#ifdef LUA_OPTIMIZE_DEBUG_USER
+#include "lobject.h"
+#include "lstate.h"
+#include "ldebug.h"
+#include "lfunc.h"
+#endif
+
 
 
 
@@ -302,6 +309,70 @@ static int luaB_loadfile (lua_State *L) {
 }
 
 
+#ifdef LUA_OPTIMIZE_DEBUG_USER
+/* stripdebug([level[, function]]).
+ * level:    1 don't discard debug
+ *           2 discard Local and Upvalue debug info
+ *           3 discard Local, Upvalue and lineno debug info.
+ * function: Function to be stripped as per setfenv except 0 not permitted.
+ * If no arguments then the current default setting is returned.
+ * If function is omitted, this is the default setting for future compiles
+ * The function returns an estimated integer count of the bytes stripped.
+ */
+static int luaB_stripdebug (lua_State *L) {
+  int level;
+
+  if (L->top == L->base) {
+    lua_pushlightuserdata(L, &luaG_stripdebug);
+    lua_gettable(L, LUA_REGISTRYINDEX);
+    if (lua_isnil(L, -1)) {
+      lua_pop(L, 1);
+      lua_pushinteger(L, LUA_OPTIMIZE_DEBUG);
+    }
+    return 1;
+  }
+
+  level = luaL_checkint(L, 1);
+  if ((level <= 0) || (level > 3)) luaL_argerror(L, 1, "must in range 1-3");
+
+  if (L->top == L->base + 1) {
+    /* Store the default level in the registry if no function parameter */
+    lua_pushlightuserdata(L, &luaG_stripdebug);
+    lua_pushinteger(L, level);
+    lua_settable(L, LUA_REGISTRYINDEX);
+    lua_settop(L,0);
+    return 0;
+  }
+
+  if (level == 1) {
+    lua_settop(L,0);
+    lua_pushinteger(L, 0);
+    return 1;
+  }
+
+  if (!lua_isfunction(L, 2)) {
+    int scope = luaL_checkint(L, 2);
+    if (scope > 0) {
+      /* if the function parameter is a +ve integer then climb to find function */
+      lua_Debug ar;
+      lua_pop(L, 1); /* pop level as getinfo will replace it by the function */
+      if (lua_getstack(L, scope, &ar)) {
+        lua_getinfo(L, "f", &ar);
+      }
+    }
+  }
+
+  if(!lua_isfunction(L, 2) || lua_iscfunction(L, -1)) luaL_argerror(L, 2, "must be a Lua Function");
+  // lua_lock(L);
+  Proto *f = clvalue(L->base + 1)->l.p;
+  // lua_unlock(L);
+  lua_settop(L,0);
+  lua_pushinteger(L, luaG_stripdebug(L, f, level, 16));
+  return 1;
+}
+#endif
+
+
 /*
 ** Reader for generic `load' function: `lua_load' uses the
 ** stack for internal stuff, so the reader cannot change the
@@ -482,6 +553,9 @@ static const luaL_Reg base_funcs[] = {
   {"select", luaB_select},
   {"setfenv", luaB_setfenv},
   {"setmetatable", luaB_setmetatable},
+#ifdef LUA_OPTIMIZE_DEBUG_USER
+  {"stripdebug", luaB_stripdebug},
+#endif
   {"tonumber", luaB_tonumber},
   {"tostring", luaB_tostring},
   {"type", luaB_type},