1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <errno.h>
30#include <unistd.h>
31
32extern "C" int ___close(int);
33
34int close(int fd) {
35  int rc = ___close(fd);
36  if (rc == -1 && errno == EINTR) {
37    // POSIX says that if close returns with EINTR, the fd must not be closed.
38    // Linus disagrees: http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
39    // The future POSIX solution is posix_close (http://austingroupbugs.net/view.php?id=529),
40    // with the state after EINTR being undefined, and EINPROGRESS for the case where close
41    // was interrupted by a signal but the file descriptor was actually closed.
42    // My concern with that future behavior is that it breaks existing code that assumes
43    // that close only returns -1 if it failed. Unlike other system calls, I have real
44    // difficulty even imagining a caller that would need to know that close was interrupted
45    // but succeeded. So returning EINTR is wrong (because Linux always closes) and EINPROGRESS
46    // is harmful because callers need to be rewritten to understand that EINPROGRESS isn't
47    // actually a failure, but will be reported as one.
48
49    // We don't restore errno because that would incur a cost (the TLS read) for every caller.
50    // Since callers don't know ahead of time whether close will legitimately fail, they need
51    // to have stashed the old errno value anyway if they plan on using it afterwards, so
52    // us clobbering errno here doesn't change anything in that respect.
53    return 0;
54  }
55  return rc;
56}
57