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Re: ioctl: FIONREAD and ENOTTY


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.

cgf

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