Undefined symbols for architecture i386:

Undefined symbols for architecture i386:
  "lua_settop(lua_State*, int)", referenced from:
      ACRPC::registerSendFunc(lua_State*, unsigned int, char const*, char const*) in ACRPC.o
  "lua_getfield(lua_State*, int, char const*)", referenced from:
      ACRPC::registerSendFunc(lua_State*, unsigned int, char const*, char const*) in ACRPC.o
  "lua_setfield(lua_State*, int, char const*)", referenced from:
      ACRPC::registerSendFunc(lua_State*, unsigned int, char const*, char const*) in ACRPC.o
  "lua_createtable(lua_State*, int, int)", referenced from:
      ACRPC::registerSendFunc(lua_State*, unsigned int, char const*, char const*) in ACRPC.o
  "lua_type(lua_State*, int)", referenced from:
      ACRPC::registerSendFunc(lua_State*, unsigned int, char const*, char const*) in ACRPC.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

还是老问题 ，所有的lua头文件都得用 extern "C" {} 包起来，我刚才使用了 
#include "lstate.h" 但是没有使用

extern "C" {

#include "lstate.h"
}
的形式，所以又报错了

解释一下为什么要这么做：
       当运行时调用lua_settop这个函数时，实际上在C++编译时会去找  _lua_settop_lua_State_int()这个方法，但是这个方法在so文件里是不存在的。所以，用extern "C" 包含起来以后，就会以C的方式编译，此时会去找 _lua_settop()，这个时候，就能找到该函数了。
       上面几个问题，依此类推。