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Re: 1.3.22-1 on XP: malloc returns overlapping buffers
- From: Larry Hall <cygwin-lh at cygwin dot com>
- To: roconnor <roconnor at hsc dot usf dot edu>
- Cc: cygwin at cygwin dot com
- Date: Wed, 20 Aug 2003 23:25:10 -0400
- Subject: Re: 1.3.22-1 on XP: malloc returns overlapping buffers
- References: <20030820200711.GA3964@delwin>
- Reply-to: cygwin at cygwin dot com
roconnor wrote:
I am finding that under some circumstances a buffer returned by malloc
will overlap with a buffer returned by a previous call to malloc that
has not been freed. I was able to reduce it to the following test
case. Running under cygwin 1.3.22-1 on Windows XP Professional
Version 2002 SP1 it reports an overlap of 4824 bytes on two different
machines, as well as on a third machine running Windows 2000 5.00.2195
SP4. On Windows NT 4.0.1381, it finds no overlap.
Am I doing something wrong or is there a bug in malloc or XP? More
details below.
------------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
int
main (int argc, char **argv)
{
char *mm = 0, *p;
int size = 8000, overlap;
p = malloc (1);
while (mm < p) {
mm = malloc (16777216);
if (mm == 0) {
printf ("not enough memory to run test\n");
exit (0);
}
printf ("malloc (16777216) = %d\n", (int)mm);
}
while ((p = malloc (size))) {
overlap = (int)p + size - (int)mm;
if (p < mm && overlap > 0) {
printf ("overlap = %d\n", overlap);
exit (1);
}
}
return 0;
}
This works OK for me on W2K SP1 with cygwin 1.5.x. Maybe you want to
upgrade to this (i.e. the test version) and see if you still see the
problem.
--
Larry Hall http://www.rfk.com
RFK Partners, Inc. (508) 893-9779 - RFK Office
838 Washington Street (508) 893-9889 - FAX
Holliston, MA 01746
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