tiny.mprompt.yieldPrompt

1/// Suspends the calling code together with `p` and each nested active prompt, so code running under2/// a prompt suspends back to the point that entered the prompt and hands a resumption to a function3/// there, as a worker does while it waits for its request. The call jumps to where `p` was entered4/// or last resumed and calls `fun(resumption, arg)` there. The return value of `fun` becomes the5/// result of the call that entered or last resumed `p`. The call returns the value passed when the6/// resumption is resumed. The call saves the registers at its own point, where a resume jumps, and7/// the frames on the suspended stacklets stay as they were. `p` must be an active prompt of the8/// calling thread, and assertions check this in safe builds. Before each jump the runtime checks9/// the saved stack pointer and jump target against the guard cookie, and a mismatch stops the10/// program with a "potential stack corruption detected" panic.11pub noinline fn yieldPrompt(p: *Prompt, fun: YieldFn, arg: ?*anyopaque) ?*anyopaque {12    assert(promptIsAncestor(p));13    assert(promptIsActive(p));1415    var res: ResumePoint = undefined;16    if (context.mp_setjmp(&res.jmp) != 0) {17        assert(promptIsActive(p));18        assert(promptIsAncestor(p));19        return res.result;20    }2122    if (resume_label == null) resume_label = guard(res.jmp.reg_ip);2324    var sp: ?*anyopaque = null;25    const ret = promptUnlink(p, &res, &sp);26    ret.fun = fun;27    ret.arg = arg;28    ret.kind = .yielded;29    checkedLongjmp(return_label, sp, &ret.jmp);30}

1pub const yieldPrompt = raw.yieldPrompt;