c++ - How can I end a Lua thread cleanly?

Question

My situation is that I'm using the Lua (C) API to execute a script held in a string. I would like the user to be able to terminate the execution of the script (this is essential if the script contains an infinite loop), how can I do this?

lua_State *Lua = lua_open();
char * code;
// Initialisation code
luaL_dostring(L, code);

Answer 1

Hook on lines is not enough. This code is a single line, but loops forever:

    while true do end

You need to set an instruction count hook. If I'm not mistaken, that would be

    lua_sethook(Lua, &LineHookFunc, LUA_MASKCOUNT, NUM_INSTRUCTIONS);

You want to pick NUM_INSTRUCTIONS so it is not too small (or you get a performance overhead) and not too large (or you'll wait too long until stop).

For related Lua-only implementation please see this library.

If you want to add more protection from untrusted Lua code, google for "Lua sandboxing" -- there is more to it than just infinite loop prevention.