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annotate lib/popen.c @ 11848:9e3299dad578

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popen: fix cygwin 1.5 bug when stdin closed * doc/posix-functions/popen.texi (popen): Document cygwin bugs. * modules/popen: New file. * modules/popen-tests: Likewise. * tests/test-popen.c: Likewise. * m4/popen.m4: Likewise. * lib/popen.c: Likewise. * lib/stdio.in.h (popen): New declaration. * m4/stdio_h.m4 (gl_STDIO_H_DEFAULTS): Add popen. * modules/stdio (Makefile.am): Likewise. * MODULES.html.sh (systems lacking POSIX:2008): Mention it. Signed-off-by: Eric Blake <ebb9@byu.net>
author Eric Blake <ebb9@byu.net>
date Wed, 19 Aug 2009 07:15:54 -0600
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children f17a5ed578bd
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11848
9e3299dad578 popen: fix cygwin 1.5 bug when stdin closed
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1 /* Open a stream to a sub-process.
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2 Copyright (C) 2009 Free Software Foundation, Inc.
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3
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4 This program is free software: you can redistribute it and/or modify
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5 it under the terms of the GNU General Public License as published by
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6 the Free Software Foundation; either version 3 of the License, or
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7 (at your option) any later version.
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8
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9 This program is distributed in the hope that it will be useful,
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10 but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 GNU General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public License
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15 along with this program. If not, see <http://www.gnu.org/licenses/>. */
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16
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17 /* Written by Eric Blake <ebb9@byu.net>, 2009. */
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18
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19 #include <config.h>
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20
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21 /* Get the original definition of popen. It might be defined as a macro. */
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22 #define __need_FILE
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23 # include <stdio.h>
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24 #undef __need_FILE
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25
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26 static inline FILE *
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27 orig_popen (const char *filename, const char *mode)
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28 {
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29 return popen (filename, mode);
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30 }
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31
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32 /* Specification. */
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33 #include <stdio.h>
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34
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35 #include <errno.h>
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36 #include <fcntl.h>
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37 #include <stdlib.h>
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38 #include <unistd.h>
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39
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40 FILE *
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41 rpl_popen (const char *filename, const char *mode)
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42 {
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43 /* The mingw popen works fine, and all other platforms have fcntl.
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44 The bug of the child clobbering its own file descriptors if stdin
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45 or stdout was closed in the parent can be worked around by
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46 opening those two fds as close-on-exec to begin with. */
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47 /* Cygwin 1.5.x also has a bug where the popen fd is improperly
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48 marked close-on-exec, and if the application undoes this, then
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49 the fd leaks into subsequent popen calls. We could work around
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50 this by maintaining a list of all fd's opened by popen, and
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51 temporarily marking them cloexec around the real popen call, but
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52 we would also have to override pclose, and the bookkeepping seems
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53 extreme given that cygwin 1.7 no longer has the bug. */
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54 FILE *result;
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55 int cloexec0 = fcntl (STDIN_FILENO, F_GETFD);
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56 int cloexec1 = fcntl (STDOUT_FILENO, F_GETFD);
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57 int saved_errno;
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58
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59 if (cloexec0 < 0)
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60 {
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61 if (open ("/dev/null", O_RDONLY) != STDIN_FILENO
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62 || fcntl (STDIN_FILENO, F_SETFD,
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63 fcntl (STDIN_FILENO, F_GETFD) | FD_CLOEXEC) == -1)
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64 abort ();
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65 }
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66 if (cloexec1 < 0)
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67 {
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68 if (open ("/dev/null", O_RDONLY) != STDOUT_FILENO
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69 || fcntl (STDOUT_FILENO, F_SETFD,
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70 fcntl (STDOUT_FILENO, F_GETFD) | FD_CLOEXEC) == -1)
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71 abort ();
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72 }
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73 result = orig_popen (filename, mode);
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74 saved_errno = errno;
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75 if (cloexec0 < 0)
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76 close (STDIN_FILENO);
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77 if (cloexec1 < 0)
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78 close (STDOUT_FILENO);
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79 errno = saved_errno;
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80 return result;
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81 }