覆盖 require 后调用 lua_getfield() 时崩溃

这个问题与 @Henri_Menke 在这个问题中的回答相关：如何在 C++ 中获取预加载模块名称 https://stackoverflow.com/questions/51510308/how-to-get-preloaded-module-name-in-c

我正在尝试覆盖require使用我自己的版本运行函数，这样我就可以在 Lua 脚本中获取预加载的模块名称。

这是我的代码：

#include "lua.hpp"

void main()
{
    lua_State *L = luaL_newstate();
    luaL_openlibs(L);
    lua_settop(L, 0);
    luaL_dostring(L, "local require_original = require\n"
                     "function require(name, ...)\n"
                         "current_module = name\n"
                         "require_original(name, ...)\n"
                         "current_module = nil\n"
                     "end\n"); //if I comment out this chunk, it works fine
    luaL_dostring(L, "package.preload['test'] = function ()\n"
                         "local test = {}\n"
                         "print('While loading:', current_module)\n"
                         "function test.update() print('Updated!') end\n"
                         "return test\n"
                     "end\n");
    lua_getglobal(L, "require");
    lua_pushstring(L, "test");
    if (lua_pcall(L, 1, LUA_MULTRET, 0))
    {
        std::cout << "Error: " << lua_tostring(L, -1) << std::endl;
        lua_pop(L, 1);
    }
    int top = lua_gettop(L);
    lua_getfield(L, -1, "update"); //crashes here
    if (lua_isfunction(L, -1))
    {
        lua_pushnil(L);
        if (lua_pcall(L, 1, LUA_MULTRET, 0))
        {
            std::cout << "Error: " << lua_tostring(L, -1) << std::endl;
            lua_pop(L, 1);
        }
    }
    lua_close(L);
}

但是调用的时候就崩溃了lua_getfield(L, -1, "update");.

当我注释掉 Lua 脚本的第一块（第一个luaL_dostring).

我不明白为什么如果我使用我自己的版本它会崩溃require.

我怎样才能解决这个问题？

我忘记从重写中返回模块表require功能。对于那个很抱歉。

#include <iostream>
#include "lua.hpp"

int main() {
    lua_State *L = luaL_newstate();
    luaL_openlibs(L);
    lua_settop(L, 0);
    luaL_dostring(L, "local require_original = require\n"
                     "function require(name, ...)\n"
                         "current_module = name\n"
                         "local val = table.pack(require_original(name, ...))\n"
                         "current_module = nil\n"
                         "return table.unpack(val,1,val.n)\n"
                     "end\n"); //if I comment out this chunk, it works fine
    luaL_dostring(L, "package.preload['test'] = function ()\n"
                         "local test = {}\n"
                         "print('While loading:', current_module)\n"
                         "function test.update() print('Updated!') end\n"
                         "return test\n"
                     "end\n");
    lua_getglobal(L, "require");
    lua_pushstring(L, "test");
    if (lua_pcall(L, 1, LUA_MULTRET, 0))
    {
        std::cout << "Error: " << lua_tostring(L, -1) << std::endl;
        lua_pop(L, 1);
    }
    int top = lua_gettop(L);
    lua_getfield(L, -1, "update"); //crashes here
    if (lua_isfunction(L, -1))
    {
        lua_pushnil(L);
        if (lua_pcall(L, 1, LUA_MULTRET, 0))
        {
            std::cout << "Error: " << lua_tostring(L, -1) << std::endl;
            lua_pop(L, 1);
        }
    }
    lua_close(L);
}

$ clang++ -Wall -Wextra -Wpedantic -I /usr/include/lua5.2 test.cpp -llua5.2
test.cpp:28:9: warning: unused variable 'top' [-Wunused-variable]
    int top = lua_gettop(L);
        ^
1 warning generated.
$ ./a.out 
While loading:  test
Updated!