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/*
Copyright 2001 Free Software Foundation, Inc.
Written by Michael Chastain, <chastain@redhat.com>
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 2 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, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
This program demonstrates a bug in cygwin's mmap.
I open one file, mmap it, and close it.
I open a different file, mmap it, and close it.
The second file re-uses the file handle (which is OK),
but then it re-uses the buffer as well! Ouch!
This bug occurs on cygwin1.dll dated 2001-01-31.
It causes gnu cpp to screw up its include file buffers.
Compile with "gcc -o y1 y1.c".
Output from a bad cygwin1.dll:
y1.txt: 3 0x4660000 y1 y1 y1 y1 y1 y1 y1
y2.txt: 3 0x4660000 y1 y1 y1 y1 y1 y1 y1
Output from a good cygwin1.dll:
y1.txt: 3 0x14060000 y1 y1 y1 y1 y1 y1 y1
y2.txt: 3 0x14070000 y2 y2 y2 y2 y2 y2 y2
Output from Red Hat Linux 7:
y1.txt: 3 0x40017000 y1 y1 y1 y1 y1 y1 y1
y2.txt: 3 0x40018000 y2 y2 y2 y2 y2 y2 y2
*/
#include <sys/mman.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
/* some systems have O_BINARY and some do not */
#ifndef O_BINARY
#define O_BINARY 0
#endif
/* filler for file 1 */
char const line1 [] = "y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1\n";
#define size1 (sizeof(line1) - 1)
#define count1 ((4096 / size1) + 1)
/* filler for file 2 */
char const line2 [] = "y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2\n";
#define size2 (sizeof(line2) - 1)
#define count2 ((4096 / size2) + 1)
int main ()
{
int fd1;
char * buf1;
int fd2;
char * buf2;
int i;
/* create file 1 */
fd1 = open ("y1.txt", O_WRONLY|O_CREAT|O_TRUNC|O_BINARY, 0644);
for (i = 0; i < count1; i++)
write (fd1, line1, size1);
close (fd1);
/* create file 2 */
fd2 = open ("y2.txt", O_WRONLY|O_CREAT|O_TRUNC|O_BINARY, 0644);
for (i = 0; i < count2; i++)
write (fd2, line2, size2);
close (fd2);
/* mmap file 1 */
fd1 = open ("y1.txt", O_RDONLY | O_BINARY, 0644);
buf1 = mmap (0, 4096, PROT_READ, MAP_PRIVATE, fd1, 0);
close (fd1);
/* mmap file 2 */
fd2 = open ("y2.txt", O_RDONLY | O_BINARY, 0644);
buf2 = mmap (0, 4096, PROT_READ, MAP_PRIVATE, fd2, 0);
close (fd2);
/* the buffers have to be different */
if (buf1 == buf2 || !memcmp (buf1, buf2, 20))
{
printf ("buffers are not different!\n");
return 1;
}
return 0;
}
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