From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <glibc-bugs-return-23800-listarch-glibc-bugs=sources.redhat.com@sourceware.org>
Received: (qmail 7069 invoked by alias); 17 Jun 2014 17:35:44 -0000
Mailing-List: contact glibc-bugs-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <glibc-bugs.sourceware.org>
List-Subscribe: <mailto:glibc-bugs-subscribe@sourceware.org>
List-Post: <mailto:glibc-bugs@sourceware.org>
List-Help: <mailto:glibc-bugs-help@sourceware.org>, <http://sourceware.org/lists.html#faqs>
Sender: glibc-bugs-owner@sourceware.org
Received: (qmail 7055 invoked by uid 48); 17 Jun 2014 17:35:40 -0000
From: "ppluzhnikov at google dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug stdio/17063] New: fclose() may fail to flush data
Date: Tue, 17 Jun 2014 17:35:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: glibc
X-Bugzilla-Component: stdio
X-Bugzilla-Version: unspecified
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: ppluzhnikov at google dot com
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at sourceware dot org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter
Message-ID: <bug-17063-131@http.sourceware.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
X-Bugzilla-URL: http://sourceware.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-SW-Source: 2014-06/txt/msg01176.txt.bz2

https://sourceware.org/bugzilla/show_bug.cgi?id=17063

            Bug ID: 17063
           Summary: fclose() may fail to flush data
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: stdio
          Assignee: unassigned at sourceware dot org
          Reporter: ppluzhnikov at google dot com

This is a followup to PR16532.

A program that does

  fopen(..., "w+");
  fwrite(...);
  fread(...);
  fclose();

may leave empty file on disk (fail to flush when it should have), when the
fread requests more than a page's worth of data.

At least glibc-2.19 through current trunk
(754c5a08aacb44895d1ab97c553ce424eb43f761) are affected.

./t
testing     3
testing     3 OK
testing     6
testing     6 OK
testing     9
testing     9 OK
testing  4095
testing  4095 OK
testing  4096
t: t.c:28: do_test: Assertion `pos == 6' failed.
Aborted

/// --- cut ---
#include <assert.h>
#include <stdio.h>

void do_test (int n)
{
  FILE *fp;
  const char *const fname = "/tmp/output";
  int nwritten, nread, pos;
  char line[8192];

  printf ("testing %5d\n", n);
  fp = fopen (fname, "w+");
  nwritten = fwrite ("abcabc", 1, 6, fp);
  assert (nwritten == 6);

  pos = ftello (fp);
  assert (pos == 6);

  nread = fread (line, 1, n, fp);
  assert (nread == 0);

  fclose (fp);

  fp = fopen (fname, "r");
  fseeko (fp, 0, SEEK_END);
  pos = ftello (fp);

  assert (pos == 6);
  printf ("testing %5d OK\n", n);
}

int main(int argc, char *argv[])
{
  int j, nreads[] = { 3, 6, 9, 4095, 4096, 4097, 8191, 8192 };

  for (j = 0; j < sizeof (nreads) / sizeof (nreads[0]); ++j)
    do_test (nreads[j]);

  return 0;
}

-- 
You are receiving this mail because:
You are on the CC list for the bug.