Re: malloc patch for overflow detection

[Andreas Jaeger <aj@arthur.rhein-neckar.de>]

>>>>> Wolfram Gloger writes:

 > OK, here is what I promised I would come up with to make even the
 > strangest malloc test programs happy.  It isn't perfect, but I can't
 > measure a significant slowdown from the non-overflow checking version
 > on Intel.  If the patch cannot be applied to current glibc (it should)
 > just yell and I will provide a line-number-clean version.

Sorry, the request2size macro isn't working correctly.  Please try the
appended test program (I wouldn't call it strange;-), it will report
that malloc (-1) still fails.

The problem with request2size is that incrementing -1 leads to a
positive value.  You might need to check req for <= 0.

Andreas

/* Copyright (C) 1999 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Andreas Jaeger <aj@arthur.rhein-neckar.de>, 1999.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <malloc.h>
#include <stdio.h>

static int errors = 0;

static void
merror (const char *msg)
{
  errors++;
  printf ("Error: %s\n", msg);
}

int
main (void)
{
  void *p;
  int save;
  
  errno = 0;
  
  p = malloc (-1);
  save = errno;
  
  if (p != NULL)
    merror ("malloc (-1) succeeded.");

  if (p == NULL && save != ENOMEM)
    merror ("errno is not set correctly");
  
  p = malloc (10);
  if (p == NULL)
    merror ("malloc (10) failed.");

  /* realloc (p, 0) == free (p).  */
  p = realloc (p, 0);
  if (p != NULL)
    merror ("realloc (p, 0) failed.");

  p = malloc (0);
  if (p == NULL)
    merror ("malloc (0) failed.");

  p = realloc (p, 0);
  if (p != NULL)
    merror ("realloc (p, 0) failed.");
  
  return (errors != 0);
}

-- 
 Andreas Jaeger   aj@arthur.rhein-neckar.de    jaeger@informatik.uni-kl.de
  for pgp-key finger ajaeger@aixd1.rhrk.uni-kl.de