Lua/Luajit: pause current Lua thread

Question

I am currently using Luajit along side Lua 5.1 and currently trying to register a function called "Wait" within the Lua C APIs. The main purpose of the function is to pause the current thread.

Example usage:

print("Working");
Wait()
print("A");

However the function does not work as expected. Here is my C++ code.

#include <iostream>
#include <Windows.h>

extern "C" {
    #include "Luajit/luajit.h"
    #include <Luajit/lua.h>
    #include <Luajit/lualib.h>
    #include <Luajit/lauxlib.h>
}


static int wait(lua_State* lua) {
    return lua_yield(lua, 0);
}

int main() {
    lua_State* lua = luaL_newstate();

    if (!lua) {
        std::cout << "Failed to create Lua state" << std::endl;
        system("PAUSE");
        return -1;
    }

luaL_openlibs(lua);
lua_register(lua, "Wait", wait);

lua_State* thread = lua_newthread(lua);

if (!thread) {
    std::cout << "Failed to create Lua thread" << std::endl;
    system("PAUSE");
    return -1;
}

int status = luaL_loadfile(thread, "Z:/Projects/Visual Studio/Examples/Lua/Debug/Main.lua");

if (status == LUA_ERRFILE) {
    std::cout << "Failed to load file" << std::endl;
    system("PAUSE");
    return -1;
}

int error = lua_pcall(thread, 0, 0, 0);

if (error) {
    std::cout << "Error: " << lua_tostring(thread, 1) << std::endl;
}

system("PAUSE");
return 0;
}

When I load up the Lua script I posted above I get the following output:

Working
Error: attempt to yield across C-call boundary
Press any key to continue . . .

I been programming in Lua for more than 4 years now. I just recently started using the C APIs and I never seen the C-call boundary error before. I did some Googling and ask friends and no one seems to be able to help me. Any idea what is wrong with my code?

The error occur when I call the lua_yield(lua, 0) function in C++.

I tried the answers of the following question and nothing seems to work.

http://stackoverflow.com/questions/8459459/lua-coroutine-error-tempt-to-yield-across-metamethod-c-call-boundary

Answer 1

lua_pcall does not start a yieldable coroutine. The proper function to start a coroutine is lua_resume.