lua_yieldk

lua_yieldk[-?, +?, e]

int lua_yieldk (lua_State *L,
                int nresults,
                lua_KContext ctx,
                lua_KFunction k);

Yields a coroutine (thread).

When a C function calls lua_yieldk, the running coroutine suspends its execution, and the call to lua_resume that started this coroutine returns. The parameter nresults is the number of values from the stack that will be passed as results to lua_resume.

When the coroutine is resumed again, Lua calls the given continuation function k to continue the execution of the C function that yielded (see §4.7). This continuation function receives the same stack from the previous function, with the n results removed and replaced by the arguments passed to lua_resume. Moreover, the continuation function receives the value ctx that was passed to lua_yieldk.

Usually, this function does not return; when the coroutine eventually resumes, it continues executing the continuation function. However, there is one special case, which is when this function is called from inside a line or a count hook (see §4.9). In that case, lua_yieldk should be called with no continuation (probably in the form of lua_yield) and no results, and the hook should return immediately after the call. Lua will yield and, when the coroutine resumes again, it will continue the normal execution of the (Lua) function that triggered the hook.

This function can raise an error if it is called from a thread with a pending C call with no continuation function, or it is called from a thread that is not running inside a resume (e.g., the main thread).