| 1 | /* cloexec.c - set or clear the close-on-exec descriptor flag |
| 2 | |
| 3 | Copyright (C) 1991, 2004-2006, 2009-2019 Free Software Foundation, Inc. |
| 4 | |
| 5 | This program is free software: you can redistribute it and/or modify |
| 6 | it under the terms of the GNU General Public License as published by |
| 7 | the Free Software Foundation; either version 3 of the License, or |
| 8 | (at your option) any later version. |
| 9 | |
| 10 | This program is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | GNU General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU General Public License |
| 16 | along with this program. If not, see <https://www.gnu.org/licenses/>. |
| 17 | |
| 18 | The code is taken from glibc/manual/llio.texi */ |
| 19 | |
| 20 | #include <config.h> |
| 21 | |
| 22 | #include "cloexec.h" |
| 23 | |
| 24 | #include <errno.h> |
| 25 | #include <fcntl.h> |
| 26 | #include <unistd.h> |
| 27 | |
| 28 | /* Set the 'FD_CLOEXEC' flag of DESC if VALUE is true, |
| 29 | or clear the flag if VALUE is false. |
| 30 | Return 0 on success, or -1 on error with 'errno' set. |
| 31 | |
| 32 | Note that on MingW, this function does NOT protect DESC from being |
| 33 | inherited into spawned children. Instead, either use dup_cloexec |
| 34 | followed by closing the original DESC, or use interfaces such as |
| 35 | open or pipe2 that accept flags like O_CLOEXEC to create DESC |
| 36 | non-inheritable in the first place. */ |
| 37 | |
| 38 | int |
| 39 | set_cloexec_flag (int desc, bool value) |
| 40 | { |
| 41 | #ifdef F_SETFD |
| 42 | |
| 43 | int flags = fcntl (desc, F_GETFD, 0); |
| 44 | |
| 45 | if (0 <= flags) |
| 46 | { |
| 47 | int newflags = (value ? flags | FD_CLOEXEC : flags & ~FD_CLOEXEC); |
| 48 | |
| 49 | if (flags == newflags |
| 50 | || fcntl (desc, F_SETFD, newflags) != -1) |
| 51 | return 0; |
| 52 | } |
| 53 | |
| 54 | return -1; |
| 55 | |
| 56 | #else /* !F_SETFD */ |
| 57 | |
| 58 | /* Use dup2 to reject invalid file descriptors; the cloexec flag |
| 59 | will be unaffected. */ |
| 60 | if (desc < 0) |
| 61 | { |
| 62 | errno = EBADF; |
| 63 | return -1; |
| 64 | } |
| 65 | if (dup2 (desc, desc) < 0) |
| 66 | /* errno is EBADF here. */ |
| 67 | return -1; |
| 68 | |
| 69 | /* There is nothing we can do on this kind of platform. Punt. */ |
| 70 | return 0; |
| 71 | #endif /* !F_SETFD */ |
| 72 | } |
| 73 | |
| 74 | |
| 75 | /* Duplicates a file handle FD, while marking the copy to be closed |
| 76 | prior to exec or spawn. Returns -1 and sets errno if FD could not |
| 77 | be duplicated. */ |
| 78 | |
| 79 | int |
| 80 | dup_cloexec (int fd) |
| 81 | { |
| 82 | return fcntl (fd, F_DUPFD_CLOEXEC, 0); |
| 83 | } |