func()

in internal/gocore/process.go [558:642]
69 lines of code
16 McCabe index (conditional complexity)

func (p *Process) readG(r region) *Goroutine {
	g := &Goroutine{r: r}
	stk := r.Field("stack")
	g.stackSize = int64(stk.Field("hi").Uintptr() - stk.Field("lo").Uintptr())

	var osT *core.Thread // os thread working on behalf of this G (if any).
	mp := r.Field("m")
	if mp.Address() != 0 {
		m := mp.Deref()
		pid := m.Field("procid").Uint64()
		// TODO check that m.curg points to g?
		for _, t := range p.proc.Threads() {
			if t.Pid() == pid {
				osT = t
			}
		}
	}
	status := r.Field("atomicstatus").Uint32()
	status &^= uint32(p.rtConstants["_Gscan"])
	var sp, pc core.Address
	switch status {
	case uint32(p.rtConstants["_Gidle"]):
		return g
	case uint32(p.rtConstants["_Grunnable"]), uint32(p.rtConstants["_Gwaiting"]):
		sched := r.Field("sched")
		sp = core.Address(sched.Field("sp").Uintptr())
		pc = core.Address(sched.Field("pc").Uintptr())
	case uint32(p.rtConstants["_Grunning"]):
		sp = osT.SP()
		pc = osT.PC()
		// TODO: back up to the calling frame?
	case uint32(p.rtConstants["_Gsyscall"]):
		sp = core.Address(r.Field("syscallsp").Uintptr())
		pc = core.Address(r.Field("syscallpc").Uintptr())
		// TODO: or should we use the osT registers?
	case uint32(p.rtConstants["_Gdead"]):
		return nil
		// TODO: copystack, others?
	default:
		// Unknown state. We can't read the frames, so just bail now.
		// TODO: make this switch complete and then panic here.
		// TODO: or just return nil?
		return g
	}
	for {
		f, err := p.readFrame(sp, pc)
		if err != nil {
			fmt.Printf("warning: giving up on backtrace: %v\n", err)
			break
		}
		if f.f.name == "runtime.goexit" {
			break
		}
		if len(g.frames) > 0 {
			g.frames[len(g.frames)-1].parent = f
		}
		g.frames = append(g.frames, f)

		if f.f.name == "runtime.sigtrampgo" {
			// Continue traceback at location where the signal
			// interrupted normal execution.
			ctxt := p.proc.ReadPtr(sp.Add(16)) // 3rd arg
			//ctxt is a *ucontext
			mctxt := ctxt.Add(5 * 8)
			// mctxt is a *mcontext
			sp = p.proc.ReadPtr(mctxt.Add(15 * 8))
			pc = p.proc.ReadPtr(mctxt.Add(16 * 8))
			// TODO: totally arch-dependent!
		} else {
			sp = f.max
			pc = core.Address(p.proc.ReadUintptr(sp - 8)) // TODO:amd64 only
		}
		if pc == 0 {
			// TODO: when would this happen?
			break
		}
		if f.f.name == "runtime.systemstack" {
			// switch over to goroutine stack
			sched := r.Field("sched")
			sp = core.Address(sched.Field("sp").Uintptr())
			pc = core.Address(sched.Field("pc").Uintptr())
		}
	}
	return g
}