1.3.22-1 on XP: malloc returns overlapping buffers
Larry Hall
cygwin-lh@cygwin.com
Thu Aug 21 03:37:00 GMT 2003
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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