110 lines
2.9 KiB
C
110 lines
2.9 KiB
C
/*
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Copyright 2001 Free Software Foundation, Inc.
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Written by Michael Chastain, <chastain@redhat.com>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA.
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This program demonstrates a bug in cygwin's mmap.
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I open one file, mmap it, and close it.
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I open a different file, mmap it, and close it.
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The second file re-uses the file handle (which is OK),
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but then it re-uses the buffer as well! Ouch!
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This bug occurs on cygwin1.dll dated 2001-01-31.
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It causes gnu cpp to screw up its include file buffers.
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Compile with "gcc -o y1 y1.c".
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Output from a bad cygwin1.dll:
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y1.txt: 3 0x4660000 y1 y1 y1 y1 y1 y1 y1
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y2.txt: 3 0x4660000 y1 y1 y1 y1 y1 y1 y1
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Output from a good cygwin1.dll:
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y1.txt: 3 0x14060000 y1 y1 y1 y1 y1 y1 y1
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y2.txt: 3 0x14070000 y2 y2 y2 y2 y2 y2 y2
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Output from Red Hat Linux 7:
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y1.txt: 3 0x40017000 y1 y1 y1 y1 y1 y1 y1
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y2.txt: 3 0x40018000 y2 y2 y2 y2 y2 y2 y2
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*/
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#include <sys/mman.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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/* some systems have O_BINARY and some do not */
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#ifndef O_BINARY
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#define O_BINARY 0
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#endif
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/* filler for file 1 */
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char const line1 [] = "y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1\n";
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#define size1 (sizeof(line1) - 1)
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#define count1 ((4096 / size1) + 1)
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/* filler for file 2 */
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char const line2 [] = "y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2 y2\n";
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#define size2 (sizeof(line2) - 1)
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#define count2 ((4096 / size2) + 1)
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int main ()
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{
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int fd1;
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char * buf1;
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int fd2;
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char * buf2;
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int i;
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/* create file 1 */
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fd1 = open ("y1.txt", O_WRONLY|O_CREAT|O_TRUNC|O_BINARY, 0644);
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for (i = 0; i < count1; i++)
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write (fd1, line1, size1);
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close (fd1);
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/* create file 2 */
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fd2 = open ("y2.txt", O_WRONLY|O_CREAT|O_TRUNC|O_BINARY, 0644);
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for (i = 0; i < count2; i++)
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write (fd2, line2, size2);
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close (fd2);
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/* mmap file 1 */
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fd1 = open ("y1.txt", O_RDONLY | O_BINARY, 0644);
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buf1 = mmap (0, 4096, PROT_READ, MAP_PRIVATE, fd1, 0);
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close (fd1);
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/* mmap file 2 */
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fd2 = open ("y2.txt", O_RDONLY | O_BINARY, 0644);
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buf2 = mmap (0, 4096, PROT_READ, MAP_PRIVATE, fd2, 0);
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close (fd2);
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/* the buffers have to be different */
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if (buf1 == buf2 || !memcmp (buf1, buf2, 20))
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{
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printf ("buffers are not different!\n");
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return 1;
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}
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return 0;
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}
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