Re: fflush() on readonly files

From: Tim Robbins (tjr_at_freebsd.org)
Date: 06/19/04

  • Next message: Andrey Chernov: "Re: fflush() on readonly files" 
    Date: Sat, 19 Jun 2004 22:01:49 +1000
To: freebsd-arch@freebsd.org

    On Sat, Jun 19, 2004 at 02:59:39PM +0400, Andrey Chernov wrote:

    > On Sat, Jun 19, 2004 at 11:56:43AM +0200, Radim Kolar wrote:
    > > Today I have stepped on another example: advancecomp (in ports):
    > > 543 * Get the size of the file.
    > > 544 */
    > > 545 long fzsize(adv_fz* f)
    > > 546 {
    > > 547 if (f->type == fz_file) {
    > > 548 struct stat st;
    > > 549 if (fflush(f->f) != 0) {
    > > 550 return -1;
    > > 551 }
    >
    > This program relies on undocumented behaviour and should be fixed in
    > anycase. Besides of that the only reasonable approach we can take is to do
    > what majority of systems does here. Since you are interested in the
    > subject, please post specific table for all main systems in the form
    > like:
    >
    > System readonly fflush() behaviour

    This has already been discussed:
    - Microsoft libraries and other libraries imitating them discard buffered
      input data (like fpurge().)
    - UNIX libc (at least 7th ed.), Solaris libc, GNU libc and products derived
      from P.J. Plauger's C library (e.g. QNX) do nothing and indicate success.
    - BSD since Torek's stdio rewrite (inc. FreeBSD and Mac OS X) indicate
      an error.

    There is no reason to change from the perfectly correct & well-documented
    behaviour BSD has had for 10-15 years. The original poster's example provides
    a good argument for this: it detects application bugs.

    Tim
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  • Next message: Andrey Chernov: "Re: fflush() on readonly files"

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