From:	"Tom Demmer" <DEMMER AT brain1 DOT lstm DOT ruhr-uni-bochum DOT de>
Organization:	Lehrstuhl Stroemungsmechanik, RUB
To:	djgpp-workers AT delorie DOT com
Date:	Thu, 27 Jun 1996 10:29:36 GMT-1
Subject:	open() / _open() bug
Reply-to:	Demmer AT LStM DOT Ruhr-Uni-Bochum DOT De
Message-ID:	<D8D0AE6C6F@brain1.lstm.ruhr-uni-bochum.de>

I think there is a subtle bug in open()/_open():
The higher bits of omode are masked out before a possibly existing 
file system extensions gets a chance to read them. Here are my 
diff -c  files that correct this. The O_TEXT/O_BINARY stuff is OK, 
may one might add in the docs that a FSE does not have to bother with 
that. I just found out by gross lazyness.

*** dos/io/_open.old    Sun Nov 26 04:47:48 1995
--- dos/io/_open.c  Thu Jun 27 14:58:16 1996
***************
*** 27,38 ****
    _put_path(filename);
    if(_USE_LFN) {
      r.x.ax = 0x716c;
!     r.x.bx = oflag;
      r.x.dx = 1;           /* Open existing file */
      r.x.si = __tb_offset;
    } else {
      r.h.ah = 0x3d;
!     r.h.al = oflag;
      r.x.dx = __tb_offset;
    }
    r.x.cx = 0;
--- 27,40 ----
    _put_path(filename);
    if(_USE_LFN) {
      r.x.ax = 0x716c;
!     r.x.bx = oflag & 0xff; /* :TOM: new open() doesn't mask out upper bits,
!                            ** so we have to do it here.
!                            */
      r.x.dx = 1;           /* Open existing file */
      r.x.si = __tb_offset;
    } else {
      r.h.ah = 0x3d;
!     r.h.al = oflag & 0xff; /* :TOM: see above */
      r.x.dx = __tb_offset;
    }
    r.x.cx = 0;

*** posix/fcntl/open.old    Mon Aug 28 01:56:46 1995
--- posix/fcntl/open.c  Thu Jun 27 15:02:40 1996
***************
*** 33,43 ****
      bintext = O_BINARY;
  
    /* DOS doesn't want to see these bits */
    oflag &= ~(O_TEXT | O_BINARY);
  
    dmode = (*((&oflag)+1) & S_IWUSR) ? 0 : 1;
  
!   fd = _open(filename, oflag & 0xff); /* only low byte used */
    if (fd == -1 && oflag & O_CREAT)
      fd = _creat(filename, dmode);
  
--- 33,44 ----
      bintext = O_BINARY;
  
    /* DOS doesn't want to see these bits */
+   /* :TOM: and an FSE does not want to see them, too, so this is OK */
    oflag &= ~(O_TEXT | O_BINARY);
  
    dmode = (*((&oflag)+1) & S_IWUSR) ? 0 : 1;
  
!   fd = _open(filename,oflag);  /* :TOM: Pass through all of oflag */
    if (fd == -1 && oflag & O_CREAT)
      fd = _creat(filename, dmode);
  

Ciao
Tom

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  *  Thomas Demmer                     * Phone : +49 234 700 6434  *
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    Standards are great. They give non-conformists something
    not to conform to.

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