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

• Skewled: Possible duplicate of Lua coroutine error: tempt to yield across metamethod/C-call boundary
• Kurieita: No, that answer didn't help.

Answer 1

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

• Kurieita: Wow. I can't believe I didn't figure that out. Thank a lot.