Re: Reading a write-only file doesn't set error condition (was Re: Cygwin fread on Write-Only File Descriptor returns undefined state)

[Jeff Johnston <jjohnstn at redhat dot com>]

Corinna Vinschen wrote:
> On Jun 14 16:57, Jeff Johnston wrote:
>
> > Jeff Johnston wrote:
> >
> > > Corinna Vinschen wrote:
> > >
> > > > So, I'd like to propose the below patch.  I assume a similar patch
> > > > should be ok for __sfvwrite, too, isn't it?  There's a call to
> > > > cantwrite() which only returns EOF but which probably should also
> > > > set the error condition and errno.
> > >
> > > This opens a can of worms.  You can't just use _REENT to set errno.  One 
> > > has to provide _r versions of the read/write functions.  I have just 
> > > made a patch and am verifying it builds for x86-linux.  I will post the 
> > > patch when I am ready to check it in.
> > >
> > > -- Jeff J.
> >
> > I have checked in the patch.  The testcase runs successfully and I am 
> > able to build/run x86-linux successfully.  Let me know if it causes any 
> > problems for Cygwin.
>
>
> Thanks for the patch, but unfortunately it does cause problems.
> I found three problems:
>
> - Typo in stdio.h, "struct _REENT" instead of "struct _reent".
> - Missing conversion from crlf to crlf_r calls in fread.c.
> - Removing __srget and __swbuf functions breaks backward compatibility.
>   Older applications built up to yesterday against a share lib version
>   of newlib will refuse to run with a newer newlib, due to missing
>   symbols __srget and __swbuf in the shared lib.

Thanks Corinna.  Patch checked in.

-- Jeff J.

> Patch below.
>
>
> Thanks,
> Corinna
>
>
> 	* libc/include/stdio.h (__sgetc_r): Fix typo.
> 	* libc/stdio/fread.c (_fread_r): Convert crlf calls to crlf_r.
> 	* libc/stdio/rget.c (__srbuf): Reinstantiate.
> 	* libc/stdio/wbuf.c (__swbuf): Ditto.
>
>
> Index: libc/include/stdio.h
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/include/stdio.h,v
> retrieving revision 1.36
> diff -u -p -r1.36 stdio.h
> --- libc/include/stdio.h	14 Jun 2006 20:49:11 -0000	1.36
> +++ libc/include/stdio.h	15 Jun 2006 12:28:24 -0000
> @@ -402,7 +402,7 @@ FILE	*_EXFUN(funopen,(const _PTR _cookie
>  #define       __sgetc_raw_r(__ptr, __f) (--(__f)->_r < 0 ? __srget_r(__ptr, __f) : (int)(*(__f)->_p++))
>  
>  #ifdef __SCLE
> -static __inline__ int __sgetc_r(struct _REENT *__ptr, FILE *__p)
> +static __inline__ int __sgetc_r(struct _reent *__ptr, FILE *__p)
>    {
>      int __c = __sgetc_raw_r(__ptr, __p);
>      if ((__p->_flags & __SCLE) && (__c == '\r'))
> Index: libc/stdio/fread.c
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/stdio/fread.c,v
> retrieving revision 1.11
> diff -u -p -r1.11 fread.c
> --- libc/stdio/fread.c	14 Jun 2006 20:49:11 -0000	1.11
> +++ libc/stdio/fread.c	15 Jun 2006 12:28:24 -0000
> @@ -196,7 +196,7 @@ _DEFUN(_fread_r, (ptr, buf, size, count,
>                if (fp->_flags & __SCLE)
>  	        {
>  	          _funlockfile (fp);
> -	          return crlf (fp, buf, total-resid, 1) / size;
> +	          return crlf_r (ptr, fp, buf, total-resid, 1) / size;
>  	        }
>  #endif
>  	      _funlockfile (fp);
> @@ -221,7 +221,7 @@ _DEFUN(_fread_r, (ptr, buf, size, count,
>  	      if (fp->_flags & __SCLE)
>  		{
>  		  _funlockfile (fp);
> -		  return crlf (fp, buf, total-resid, 1) / size;
> +		  return crlf_r (ptr, fp, buf, total-resid, 1) / size;
>  		}
>  #endif
>  	      _funlockfile (fp);
> @@ -238,7 +238,7 @@ _DEFUN(_fread_r, (ptr, buf, size, count,
>    if (fp->_flags & __SCLE)
>      {
>        _funlockfile (fp);
> -      return crlf(fp, buf, total, 0) / size;
> +      return crlf_r(ptr, fp, buf, total, 0) / size;
>      }
>  #endif
>    _funlockfile (fp);
> Index: libc/stdio/rget.c
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/stdio/rget.c,v
> retrieving revision 1.3
> diff -u -p -r1.3 rget.c
> --- libc/stdio/rget.c	14 Jun 2006 20:49:11 -0000	1.3
> +++ libc/stdio/rget.c	15 Jun 2006 12:28:24 -0000
> @@ -43,3 +43,13 @@ _DEFUN(__srget_r, (ptr, fp),
>      }
>    return EOF;
>  }
> +
> +/* This function isn't any longer declared in stdio.h, but it's
> +   required for backward compatibility with applications built against
> +   earlier dynamically built newlib libraries. */
> +int
> +_DEFUN(__srget, (fp),
> +       register FILE *fp)
> +{
> +  return __srget_r (_REENT, fp);
> +}
> Index: libc/stdio/wbuf.c
> ===================================================================
> RCS file: /cvs/src/src/newlib/libc/stdio/wbuf.c,v
> retrieving revision 1.4
> diff -u -p -r1.4 wbuf.c
> --- libc/stdio/wbuf.c	14 Jun 2006 20:49:11 -0000	1.4
> +++ libc/stdio/wbuf.c	15 Jun 2006 12:28:24 -0000
> @@ -85,3 +85,14 @@ _DEFUN(__swbuf_r, (ptr, c, fp),
>        return EOF;
>    return c;
>  }
> +
> +/* This function isn't any longer declared in stdio.h, but it's
> +   required for backward compatibility with applications built against
> +   earlier dynamically built newlib libraries. */
> +int
> +_DEFUN(__swbuf, (c, fp),
> +       register int c _AND
> +       register FILE *fp)
> +{
> +  return __swbuf_r (_REENT, c, fp);
> +}