Date: Thu, 21 Jul 2011 16:22:08 -0400
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: ioctl: FIONREAD and ENOTTY
Message-ID: <20110721202208.GA12787@ednor.casa.cgf.cx>
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On Thu, Jul 21, 2011 at 03:57:46PM -0400, Christopher Faylor wrote:
>On Thu, Jul 21, 2011 at 07:47:17PM +0200, Corinna Vinschen wrote:
>>On Jul 21 13:05, Christopher Faylor wrote:
>>> On Thu, Jul 21, 2011 at 04:39:31PM +0200, Corinna Vinschen wrote:
>>> >On Jul 20 17:37, Yaakov (Cygwin/X) wrote:
>>> >> On Wed, 2011-07-20 at 17:46 +0200, Corinna Vinschen wrote:
>>> >> > On Jul 20 03:11, Yaakov (Cygwin/X) wrote:
>>> >> > > On Linux, ioctl(2) returns several different errors[1]:
>>> >> > > 
>>> >> > > EBADF  d is not a valid descriptor.
>>> >> > > EFAULT argp references an inaccessible memory area.
>>> >> > > EINVAL Request or argp is not valid.
>>> >> > > ENOTTY d is not associated with a character special device.
>>> >> > > ENOTTY The specified request does not apply to the kind of object that
>>> >> > >        the descriptor d references.
>>> >> > > 
>>> >> > > In the case of FIONREAD, Cygwin doesn't seem to distinguish between
>>> >> > > EINVAL and ENOTTY, and this causes at least one major bug:
>>> >> > > 
>>> >> > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35536
>>> >> > > 
>>> >> > > I have patched GCJ and GNU classpath to work around it, but this really
>>> >> > > needs to be fixed in Cygwin itself.
>>> >> > 
>>> >> > Would this patch be sufficient?
>>> >> > 
>>> >> > Index: fhandler.cc
>>> >> > ===================================================================
>>> >> > RCS file: /cvs/src/src/winsup/cygwin/fhandler.cc,v
>>> >> > retrieving revision 1.397
>>> >> > diff -u -p -r1.397 fhandler.cc
>>> >> > --- fhandler.cc	5 Jul 2011 12:02:10 -0000	1.397
>>> >> > +++ fhandler.cc	20 Jul 2011 15:46:40 -0000
>>> >> > @@ -1151,6 +1151,10 @@ fhandler_base::ioctl (unsigned int cmd, 
>>> >> >        set_nonblocking (*(int *) buf);
>>> >> >        res = 0;
>>> >> >        break;
>>> >> > +    case FIONREAD:
>>> >> > +      set_errno (ENOTTY);
>>> >> > +      res = -1;
>>> >> > +      break;
>>> >> >      default:
>>> >> >        set_errno (EINVAL);
>>> >> >        res = -1;
>>> >> 
>>> >> Given my testcases, give me a few days to check this out.
>>> >
>>> >Ok, but the patch doesn't build as is.  You have to add
>>> >
>>> >  #include <asm/socket.h>
>>> >
>>> >to get the FIONREAD definition.  Sorry about that.
>>> 
>>> Btw, I don't think the above is sufficient.  I think you'll have to add a
>>> similar test to other fhandlers (like fhandler_windows) which completely
>>> implement ioctl without reverting to fhandler_base.
>>
>>Hmm, isn't that just a bug in these ioctl methods?  I think they
>>all should fall through to fhandler_base::ioctl.
>
>Yep.  I think you're right.  I'll handle that if you want.

I made this modification and added the above patch as well.  We can
always pull it out or modify it if it doesn't do the right thing.

A snapshot is building now.

cgf

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