Re: Exit one Lua state from a (C) API function

[bel <bel2125@...>]

Another acceptable solution might be to allow calling the my_exit function only in cases where yield is allowed and return false otherwise.

Probably this can be done with "lua_isyieldable"


But I'm open for all suggestions that will solve the problem.

On Tue, Mar 2, 2021 at 6:59 AM bel <bel2125@gmail.com> wrote:

> Observe, however, that [B] does not make the latter available to the
> Lua state. So the coroutine in [B] simply fails when trying to call a
> nil value, and my_pcall() is never called at all.

Thank you, I missed that indeed.

Registering "my_pcall" as well changes the behavior and the "no longer unreachable" code after pcall is called.

> I would like to point out that for whatever strange reason you seem
> determined to say that lua_pcall() or Lua's reference manual have a
> bug, ...

No, that is not what I said.

I'm trying to find a solution to a specific problem - either by building a solution around Lua

or by modifying the Lua kernel itself if there is no other solution.

The program should help to test out if a particular solution works or not.

Or by documenting the restrictions which might exclude using some existing libraries.

On Mon, Mar 1, 2021 at 11:50 PM Viacheslav Usov <via.usov@gmail.com> wrote:

On Mon, Mar 1, 2021 at 7:55 PM bel <bel2125@gmail.com> wrote:

[A]

> int my_pcall(lua_State *L)
> {
>   lua_pcall(L, lua_gettop(L)-1, 0, 0);
>   UNREACHABLE
>   return 0;
> }

[B]

> int num_from_lua(const char *code)
> {
>   lua_State *L = luaL_newstate();  /* create state */
>   luaL_openlibs(L);
>   lua_pushcfunction(L, my_exit);
>   lua_setglobal(L, "my_exit");
>   lua_pushcfunction(L, my_pcallk);
>   lua_setglobal(L, "my_pcallk");
>
>   luaL_loadstring(L, code);
>   int result = setjmp(JUMP_TO_EXIT);
>   if (result) {
>       return result;
>   }
>   int status = lua_pcall(L, 0, 1, 0);
>   if (status) {
>     printf("%s\n", lua_tostring(L, 1));
>   } else {
>     result = lua_tonumber(L, -1);
>   }
>   lua_close(L);
>   return result;
> }

[C]

>   a = num_from_lua(
>     "co = coroutine.create("
>     "  function () "
>     "    my_pcall(coroutine.yield) "
>     "  end"
>     "); "
>     "coroutine.resume(co); "
>     "print(coroutine.status(co)); "
>     "return 32;"
>   );
>   check(a, 32);

Apparently you believe that [C] would call my_pcall() as defined in [A].

Observe, however, that [B] does not make the latter available to the
Lua state. So the coroutine in [B] simply fails when trying to call a
nil value, and my_pcall() is never called at all.

I would like to point out that for whatever strange reason you seem
determined to say that lua_pcall() or Lua's reference manual have a
bug, you should submit a bug report that demonstrates just this one
bug, not a program doing all kinds of things, which is so confusing
that you ended up confusing yourself.

Cheers,
V.