1# fcntl.m4 serial 9
2dnl Copyright (C) 2009-2019 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7# For now, this module ensures that fcntl()
8# - supports F_DUPFD correctly
9# - supports or emulates F_DUPFD_CLOEXEC
10# - supports F_GETFD
11# Still to be ported to mingw:
12# - F_SETFD
13# - F_GETFL, F_SETFL
14# - F_GETOWN, F_SETOWN
15# - F_GETLK, F_SETLK, F_SETLKW
16AC_DEFUN([gl_FUNC_FCNTL],
17[
18  dnl Persuade glibc to expose F_DUPFD_CLOEXEC.
19  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
20  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
21  AC_REQUIRE([AC_CANONICAL_HOST])
22  AC_CHECK_FUNCS_ONCE([fcntl])
23  if test $ac_cv_func_fcntl = no; then
24    gl_REPLACE_FCNTL
25  else
26    dnl cygwin 1.5.x F_DUPFD has wrong errno, and allows negative target
27    dnl haiku alpha 2 F_DUPFD has wrong errno
28    AC_CACHE_CHECK([whether fcntl handles F_DUPFD correctly],
29      [gl_cv_func_fcntl_f_dupfd_works],
30      [AC_RUN_IFELSE(
31         [AC_LANG_PROGRAM(
32            [[#include <errno.h>
33              #include <fcntl.h>
34              #include <limits.h>
35              #include <sys/resource.h>
36              #include <unistd.h>
37              #ifndef RLIM_SAVED_CUR
38              # define RLIM_SAVED_CUR RLIM_INFINITY
39              #endif
40              #ifndef RLIM_SAVED_MAX
41              # define RLIM_SAVED_MAX RLIM_INFINITY
42              #endif
43            ]],
44            [[int result = 0;
45              int bad_fd = INT_MAX;
46              struct rlimit rlim;
47              if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
48                  && 0 <= rlim.rlim_cur && rlim.rlim_cur <= INT_MAX
49                  && rlim.rlim_cur != RLIM_INFINITY
50                  && rlim.rlim_cur != RLIM_SAVED_MAX
51                  && rlim.rlim_cur != RLIM_SAVED_CUR)
52                bad_fd = rlim.rlim_cur;
53              if (fcntl (0, F_DUPFD, -1) != -1) result |= 1;
54              if (errno != EINVAL) result |= 2;
55              if (fcntl (0, F_DUPFD, bad_fd) != -1) result |= 4;
56              if (errno != EINVAL) result |= 8;
57              /* On OS/2 kLIBC, F_DUPFD does not work on a directory fd */
58              {
59                int fd;
60                fd = open (".", O_RDONLY);
61                if (fd == -1)
62                  result |= 16;
63                else if (fcntl (fd, F_DUPFD, STDERR_FILENO + 1) == -1)
64                  result |= 32;
65
66                close (fd);
67              }
68              return result;]])],
69         [gl_cv_func_fcntl_f_dupfd_works=yes],
70         [gl_cv_func_fcntl_f_dupfd_works=no],
71         [case $host_os in
72            aix* | cygwin* | haiku*)
73               gl_cv_func_fcntl_f_dupfd_works="guessing no" ;;
74            *) gl_cv_func_fcntl_f_dupfd_works="guessing yes" ;;
75          esac])])
76    case $gl_cv_func_fcntl_f_dupfd_works in
77      *yes) ;;
78      *) gl_REPLACE_FCNTL
79        AC_DEFINE([FCNTL_DUPFD_BUGGY], [1], [Define this to 1 if F_DUPFD
80          behavior does not match POSIX]) ;;
81    esac
82
83    dnl Many systems lack F_DUPFD_CLOEXEC
84    AC_CACHE_CHECK([whether fcntl understands F_DUPFD_CLOEXEC],
85      [gl_cv_func_fcntl_f_dupfd_cloexec],
86      [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
87#include <fcntl.h>
88#ifndef F_DUPFD_CLOEXEC
89choke me
90#endif
91         ]])],
92         [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
93#ifdef __linux__
94/* The Linux kernel only added F_DUPFD_CLOEXEC in 2.6.24, so we always replace
95   it to support the semantics on older kernels that failed with EINVAL.  */
96choke me
97#endif
98           ]])],
99           [gl_cv_func_fcntl_f_dupfd_cloexec=yes],
100           [gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])],
101         [gl_cv_func_fcntl_f_dupfd_cloexec=no])])
102    if test "$gl_cv_func_fcntl_f_dupfd_cloexec" != yes; then
103      gl_REPLACE_FCNTL
104      dnl No witness macro needed for this bug.
105    fi
106  fi
107  dnl Replace fcntl() for supporting the gnulib-defined fchdir() function,
108  dnl to keep fchdir's bookkeeping up-to-date.
109  m4_ifdef([gl_FUNC_FCHDIR], [
110    gl_TEST_FCHDIR
111    if test $HAVE_FCHDIR = 0; then
112      gl_REPLACE_FCNTL
113    fi
114  ])
115])
116
117AC_DEFUN([gl_REPLACE_FCNTL],
118[
119  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
120  AC_CHECK_FUNCS_ONCE([fcntl])
121  if test $ac_cv_func_fcntl = no; then
122    HAVE_FCNTL=0
123  else
124    REPLACE_FCNTL=1
125  fi
126])
127