Forcing a Lua script to exit

Question

How do you end a long running Lua script?

I have two threads, one runs the main program and the other controls a user supplied Lua script. I need to kill the thread

Answer 1

You could use setjmp and longjump, just like the Lua library does internally. That will get you out of pcalls and stuff just fine without need to continuously error, preventing the script from attempting to handle your bogus errors and still getting you out of execution. (I have no idea how well this plays with threads though.)

#include 
#include 
#include "lua.h"
#include "lualib.h"
#include "lauxlib.h"

jmp_buf place;

void hook(lua_State* L, lua_Debug *ar)
{
    static int countdown = 10;
    if (countdown > 0)
    {
        --countdown;
        printf("countdown: %d!\n", countdown);
    }
    else
    {
        longjmp(place, 1);
    }
}

int main(int argc, const char *argv[])
{
    lua_State* L = luaL_newstate();
    luaL_openlibs(L);
    lua_sethook(L, hook, LUA_MASKCOUNT, 100);

    if (setjmp(place) == 0)
        luaL_dostring(L, "function test() pcall(test) print 'recursing' end pcall(test)");

    lua_close(L);
    printf("Done!");
    return 0;
}