Re: [PATCH] fprintf-posix: fix memory leak

[Bruno Haible]

Hi,

On 2009-12-15, we fixed a memory leak in the fprintf replacement. Since it
is quite important to not reintroduce this bug in the future, I'm adding a
unit test against it.

>   - Limit the allowed total memory through a setrlimit call
>     (cf. tests/test-printf-posix2.c).
>   - Run the test in a loop. Determine the iteration count so that when
>     the bug is present, the memory would exceed the limit. Of course,
>     also consider the running time of the test when the bug is fixed.

2009-12-19  Bruno Haible  <address@hidden>

        fprintf-posix: Check against memory leak fixed on 2009-12-15.
        * tests/test-fprintf-posix3.sh: New file.
        * tests/test-fprintf-posix3.c: New file.
        * modules/fprintf-posix-tests (Files): Add them.
        (Makefile.am): Augment TESTS and CHECK_PROGRAMS.

======================== tests/test-fprintf-posix3.sh ========================
#!/bin/sh

# Test against a memory leak.

(./test-fprintf-posix3${EXEEXT} 0
 result=$?
 if test $result != 77 && test $result != 78; then result=1; fi
 exit $result
) 2>/dev/null
malloc_result=$?
if test $malloc_result = 77; then
  echo "Skipping test: getrlimit and setrlimit don't work"
  exit 77
fi

./test-fprintf-posix3${EXEEXT} 1 > /dev/null
result=$?
if test $result = 77; then
  echo "Skipping test: getrlimit and setrlimit don't work"
  exit 77
fi
if test $result != 0; then
  exit 1
fi

if test $malloc_result = 78; then
  echo "Skipping test: getrlimit and setrlimit don't work"
  exit 77
fi

exit 0
========================= tests/test-fprintf-posix3.c =========================
/* Test of POSIX compatible fprintf() function.
   Copyright (C) 2009 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible <address@hidden>, 2009.  */

#include <config.h>

#include <stdio.h>

#if HAVE_GETRLIMIT && HAVE_SETRLIMIT

#include <stdlib.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <string.h>
#include <errno.h>

/* Test against a memory leak in the fprintf replacement.  */

/* Number of iterations across the loop.  */
#define NUM_ROUNDS 1000

/* Number of bytes that are allowed to escape per round.  */
#define MAX_ALLOC_ROUND 10000

/* Number of bytes that are allowed to escape in total.
   This should be at least 10 MB, since it includes the normal memory
   or address space of the test program.  */
#define MAX_ALLOC_TOTAL (NUM_ROUNDS * MAX_ALLOC_ROUND)

int
main (int argc, char *argv[])
{
  struct rlimit limit;
  int arg;
  int repeat;

  /* Limit the amount of malloc()ed memory to MAX_ALLOC_TOTAL or less.  */

  /* On BSD systems, malloc() is limited by RLIMIT_DATA.  */
#ifdef RLIMIT_DATA
  if (getrlimit (RLIMIT_DATA, &limit) < 0)
    return 77;
  if (limit.rlim_max == RLIM_INFINITY || limit.rlim_max > MAX_ALLOC_TOTAL)
    limit.rlim_max = MAX_ALLOC_TOTAL;
  limit.rlim_cur = limit.rlim_max;
  if (setrlimit (RLIMIT_DATA, &limit) < 0)
    return 77;
#endif
  /* On Linux systems, malloc() is limited by RLIMIT_AS.  */
#ifdef RLIMIT_AS
  if (getrlimit (RLIMIT_AS, &limit) < 0)
    return 77;
  if (limit.rlim_max == RLIM_INFINITY || limit.rlim_max > MAX_ALLOC_TOTAL)
    limit.rlim_max = MAX_ALLOC_TOTAL;
  limit.rlim_cur = limit.rlim_max;
  if (setrlimit (RLIMIT_AS, &limit) < 0)
    return 77;
#endif

  arg = atoi (argv[1]);
  if (arg == 0)
    {
      void *memory = malloc (MAX_ALLOC_TOTAL);
      if (memory == NULL)
        return 1;
      memset (memory, 17, MAX_ALLOC_TOTAL);
      return 78;
    }

  /* Perform the test and test whether it triggers a permanent memory
     allocation of more than MAX_ALLOC_TOTAL bytes.  */

  for (repeat = 0; repeat < NUM_ROUNDS; repeat++)
    {
      /* This may produce a temporary memory allocation of 11000 bytes.
         but should not result in a permanent memory allocation.  */
      if (fprintf (stdout, "%011000d\n", 17) == -1
          && errno == ENOMEM)
        return 1;
    }

  return 0;
}

#else

int
main (int argc, char *argv[])
{
  return 77;
}

#endif
===============================================================================
--- modules/fprintf-posix-tests.orig    2009-12-19 22:09:44.000000000 +0100
+++ modules/fprintf-posix-tests 2009-12-19 21:04:03.000000000 +0100
@@ -5,6 +5,8 @@
 tests/test-printf-posix.output
 tests/test-fprintf-posix2.sh
 tests/test-fprintf-posix2.c
+tests/test-fprintf-posix3.sh
+tests/test-fprintf-posix3.c
 
 Depends-on:
 stdint
@@ -13,6 +15,6 @@
 AC_CHECK_FUNCS_ONCE([getrlimit setrlimit])
 
 Makefile.am:
-TESTS += test-fprintf-posix.sh test-fprintf-posix2.sh
+TESTS += test-fprintf-posix.sh test-fprintf-posix2.sh test-fprintf-posix3.sh
 TESTS_ENVIRONMENT += EXEEXT='@EXEEXT@' srcdir='$(srcdir)'
-check_PROGRAMS += test-fprintf-posix test-fprintf-posix2
+check_PROGRAMS += test-fprintf-posix test-fprintf-posix2 test-fprintf-posix3