Re: Bug in Control-d handling?

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

On Jun 20 09:24, Ken Brown wrote:
> On 6/20/2022 6:22 AM, Takashi Yano wrote:
> > On Mon, 20 Jun 2022 17:59:35 +0900
> > Takashi Yano wrote:
> > > Isn't this a bug of newlib? Try following code.
> > > 
> > > #include <stdio.h>
> > > 
> > > int main()
> > > {
> > > 	printf("%d\n", getchar());
> > > 	printf("%d\n", feof(stdin));
> > > 	printf("%d\n", getchar());
> > > 	return 0;
> > > }
> > > 
> > > If you press Ctrl-D at the first getchar(), the second getchar()
> > > does not return EOF while it does in linux.
> > > 
> > > The following patch seems to resolve the issue.
> > > 
> > > diff --git a/newlib/libc/stdio/refill.c b/newlib/libc/stdio/refill.c
> > > index ccedc7af7..843163b7e 100644
> > > --- a/newlib/libc/stdio/refill.c
> > > +++ b/newlib/libc/stdio/refill.c
> > > @@ -47,11 +47,9 @@ __srefill_r (struct _reent * ptr,
> > >     fp->_r = 0;			/* largely a convenience for callers */
> > > -#ifndef __CYGWIN__
> > >     /* SysV does not make this test; take it out for compatibility */
> > >     if (fp->_flags & __SEOF)
> > >       return EOF;
> > > -#endif
> > >     /* if not already reading, have to be reading and writing */
> > >     if ((fp->_flags & __SRD) == 0)
> > > 
> > > However, I am not sure what this #ifndef __CYGWIN__ is for.
> > 
> > Ah, I confirmed that System V (Solaris 11.4) behaves like that.
> > Does cygwin aim for System V compatibility???
> 
> Thanks for tracking this down!
> 
> I don't recall any situation in which Cygwin preferred System V
> compatibility over Linux compatibility.  I'm attaching the commit (from
> November 2004) in which the #ifndef __CYGWIN__ was introduced.  There's no
> indication in the commit message as to the reason for the change.  I also
> didn't see anything relevant in the cygwin or cygwin-developers mailing
> lists from November 2004, but I might have missed it.
> 
> I think that commit should probably be reverted, but we should wait until
> Corinna is available.  Even though the issue is in newlib code, the code
> only affects Cygwin, so there's probably no need to involve the newlib list.
> But again, that's Corinna's call.

I think reverting this patch makes sense these days.

Thanks for tracking this down, please push this on the master branch.


Thanks,
Corinna




> 
> Ken

> From 1f8f7e2d54364bd2993892adffb5c6435f53167d Mon Sep 17 00:00:00 2001
> From: Christopher Faylor <me@cgf.cx>
> Date: Wed, 17 Nov 2004 17:02:10 +0000
> Subject: [PATCH] * libc/stdio/refill.c (__srefill): Try again after EOF on
>  Cygwin.  Clear EOF flag if successful.
> 
> ---
>  newlib/ChangeLog           | 5 +++++
>  newlib/libc/stdio/refill.c | 8 ++++++++
>  2 files changed, 13 insertions(+)
> 
> diff --git a/newlib/ChangeLog b/newlib/ChangeLog
> index 9983e6ba6..8b8cf4d4c 100644
> --- a/newlib/ChangeLog
> +++ b/newlib/ChangeLog
> @@ -1,3 +1,8 @@
> +2004-11-17  Christopher Faylor  <cgf@timesys.com>
> +
> +	* libc/stdio/refill.c (__srefill): Try again after EOF on Cygwin.  Clear
> +	EOF flag if successful.
> +
>  2004-10-28  Christopher Faylor  <cgf@timesys.com>
>  
>  	* libc/include/sys/signal.h: Move <signal.h> include to bottom of file
> diff --git a/newlib/libc/stdio/refill.c b/newlib/libc/stdio/refill.c
> index 74573e8fd..3f0b1a566 100644
> --- a/newlib/libc/stdio/refill.c
> +++ b/newlib/libc/stdio/refill.c
> @@ -45,9 +45,11 @@ _DEFUN(__srefill, (fp),
>  
>    fp->_r = 0;			/* largely a convenience for callers */
>  
> +#ifndef __CYGWIN__
>    /* SysV does not make this test; take it out for compatibility */
>    if (fp->_flags & __SEOF)
>      return EOF;
> +#endif
>  
>    /* if not already reading, have to be reading and writing */
>    if ((fp->_flags & __SRD) == 0)
> @@ -98,7 +100,13 @@ _DEFUN(__srefill, (fp),
>    fp->_p = fp->_bf._base;
>    fp->_r = (*fp->_read) (fp->_cookie, (char *) fp->_p, fp->_bf._size);
>    fp->_flags &= ~__SMOD;	/* buffer contents are again pristine */
> +#ifndef __CYGWIN__
>    if (fp->_r <= 0)
> +#else
> +  if (fp->_r > 0)
> +    fp->_flags &= ~__SEOF;
> +  else
> +#endif
>      {
>        if (fp->_r == 0)
>  	fp->_flags |= __SEOF;
> -- 
> 2.36.1
> 

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