Start a Lua coroutine from C (with a function that can yield) - Lua5.1

lcoroc.c

#include <stdio.h>
#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>

static int
doyield (lua_State *T)
{
    return lua_yield (T, 0);
}

int main (int argc, char *argv[])
{
    lua_State *L = luaL_newstate();
    int ret;
    char *file = "testcoro.lua";

    luaL_openlibs(L);
    /* Register a C function which does a yield*/
    lua_register(L, "yieldme" , doyield);
    
    /* Load the Lua chunk on the main state */
    if (luaL_dofile(L, file) != 0) { 
        fprintf(stderr,"Failed to load file\n");
        exit(1);
    }

    lua_State *l1 = lua_newthread(L);
    
    lua_getglobal(l1, "corobegin"); // coro start func
    // push args if any 
    do {
        ret = lua_resume(l1, 0); // no args 
        if (pret == LUA_YIELD) {
            // nothing much
        } else if (pret == 0) {
            // coro ended with no errors 
        } else {
            fprintf(stderr, "\nFailed to resume: %s\n", lua_tostring(l1, -1));
        }
    } while (ret == LUA_YIELD);

    return 0;
}

#if 0 
testcoro.lua:

function corobegin
  for i=1,5 do
    yieldme()
  end
end

#endif