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From: =?UTF-8?Q?=c3=85ke_Rehnman?= <ake DOT rehnman AT gmail DOT com>
Subject: Incorrect behavior in TIOCINQ ioctl
Message-ID: <d6a35f8b-3e4d-c8c6-4d3c-f15ccd72866d@gmail.com>
Date: Thu, 27 Feb 2020 22:38:48 +0100
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Hi,

I recently ran in to some troubles with the TIOCINQ ioctl. I am 
wondering if the cygwin implementation is correct... It seems if there 
were any existing framing overrun errors etc etc  before calling the 
TIOCINQ ioctl it is returning an error (EINVAL). Reading through linux 
implmentation of TIOCINQ does simply return number of pending chars 
without any clearing or checking for errors.

I suggest the whole if (ev & CE_FRAME  ...... ) is removed.

Excerpt from fhandler_serial.cc:

/* ioctl: */
int
fhandler_serial::ioctl (unsigned int cmd, void *buf)
{
.
.
   if (!ClearCommError (get_handle (), &ev, &st))
     {
       __seterrno ();
       res = -1;
     }
.
.
.
      case TIOCINQ:
        if (ev & CE_FRAME || ev & CE_IOE || ev & CE_OVERRUN || ev & 
CE_RXOVER
        || ev & CE_RXPARITY)
      {
        set_errno (EINVAL);    /* FIXME: Use correct errno */
        res = -1;
      }
      else
         ipbuf = st.cbInQue;
      break;


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