1 /* $NetBSD: dup2_pass_on_exec.c,v 1.2 2022/10/08 16:12:50 christos Exp $ */
2
3 /*++
4 /* NAME
5 /* dup2_pass_on_exec 1
6 /* SUMMARY
7 /* dup2 close-on-exec behavior test program
8 /* SYNOPSIS
9 /* dup2_pass_on_exec
10 /* DESCRIPTION
11 /* dup2_pass_on_exec sets the close-on-exec flag on its
12 /* standard input and then dup2() to duplicate it.
13 /* Posix-1003.1 specifies in section 6.2.1.2 that dup2(o,n) should behave
14 /* as: close(n); n = fcntl(o, F_DUPFD, n); as long as o is a valid
15 /* file-descriptor, n!=o, and 0<=n<=[OPEN_MAX].
16 /* Section 6.5.2.2 states that the close-on-exec flag of the result of a
17 /* successful fcntl(o, F_DUPFD, n) is cleared.
18 /*
19 /* At least Ultrix4.3a does not clear the close-on-exec flag of n on
20 /* dup2(o, n).
21 /* DIAGNOSTICS
22 /* Problems are reported to the standard error stream.
23 /* LICENSE
24 /* .ad
25 /* .fi
26 /* The Secure Mailer license must be distributed with this software.
27 /* AUTHOR(S)
28 /* Christian von Roques <roques@pond.sub.org>
29 /* Forststrasse 71
30 /* 76131 Karlsruhe, GERMANY
31 /*--*/
32
33 #include <stdio.h>
34 #include <fcntl.h>
35 #include <unistd.h>
36 #include <stdlib.h>
37
38 #define DO(s) if (s < 0) { perror(#s); exit(1); }
39
main(int unused_argc,char ** unused_argv)40 int main(int unused_argc, char **unused_argv)
41 {
42 int res;
43
44 printf("Setting the close-on-exec flag of file-descriptor 0.\n");
45 DO(fcntl(0, F_SETFD, 1));
46
47 printf("Duplicating file-descriptor 0 to 3.\n");
48 DO(dup2(0, 3));
49
50 printf("Testing if the close-on-exec flag of file-descriptor 3 is set.\n");
51 DO((res = fcntl(3, F_GETFD, 0)));
52 if (res & 1)
53 printf(
54 "Yes, a newly dup2()ed file-descriptor has the close-on-exec \
55 flag cloned.\n\
56 THIS VIOLATES Posix1003.1 section 6.2.1.2 or 6.5.2.2!\n\
57 You should #define DUP2_DUPS_CLOSE_ON_EXEC in sys_defs.h \
58 for your OS.\n");
59 else
60 printf(
61 "No, a newly dup2()ed file-descriptor has the close-on-exec \
62 flag cleared.\n\
63 This complies with Posix1003.1 section 6.2.1.2 and 6.5.2.2!\n");
64
65 return 0;
66 }
67