--- /dev/null
+/*
+ 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))
+ return 1;
+
+ return 0;
+}
+