[PATCH v2] Cygwin: pty: Revise code waiting for forwarding again.

[Takashi Yano]

On Sun, 26 Jan 2020 22:33:19 +0900
Takashi Yano wrote:
> On Sat, 25 Jan 2020 20:38:37 +0900
> Takashi Yano wrote:
> > On Fri, 24 Jan 2020 12:07:30 +0100
> > Corinna Vinschen wrote:
> > > Too bad.  It's pretty strange that CreatePseudoConsole returns a
> > > valid HPCON but then isn't ready to take input immediately.
> > > 
> > > > I do not come up with other implementation so far.
> > > > 
> > > > Let me consider a while.
> > > 
> > > I wonder how others solve this problem.  I see that the native OpenSSH
> > > is using Sleeps, too, in their start_with_pty() function, calling
> > > AttachConsole in a loop, but I'm not sure if these are related to pseudo
> > > console usage.  The commit message don't explain anything there :(
> > 
> > The essence of the difficulty is that we have to support both cygwin
> > programs and native console apps. If we consider only of native console
> > apps, any time we can use pseudo console. However, pseudo console is
> > not transparent at all, so it cannot be used for cygwin programs.
> > 
> > Therefore, current cygwin is switching handles to be used between
> > named-pipe and pseudo console.
> > 
> > However, because pseudo console has relatively long latency, if pipe
> > is switched just after writing to pseudo console, the forwarding
> > does not get in time. So the "wait" is needed before switching.
> > 
> > I had tried WriteFile(), ReadFile() and DeviceIoControl() for
> > HANDLE hConDrvReference, however, all atempts of them failed.
> 
> After much struggle, I finally found a solution.
> Please look at v3 patch.

v3 patch does not seem to work as expected in Win10 1809.
I will submit v4 patch.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>