1# fcntl.m4 serial 11
2dnl Copyright (C) 2009-2021 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              ]GL_MDA_DEFINES[
38              #ifndef RLIM_SAVED_CUR
39              # define RLIM_SAVED_CUR RLIM_INFINITY
40              #endif
41              #ifndef RLIM_SAVED_MAX
42              # define RLIM_SAVED_MAX RLIM_INFINITY
43              #endif
44            ]],
45            [[int result = 0;
46              int bad_fd = INT_MAX;
47              struct rlimit rlim;
48              if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
49                  && 0 <= rlim.rlim_cur && rlim.rlim_cur <= INT_MAX
50                  && rlim.rlim_cur != RLIM_INFINITY
51                  && rlim.rlim_cur != RLIM_SAVED_MAX
52                  && rlim.rlim_cur != RLIM_SAVED_CUR)
53                bad_fd = rlim.rlim_cur;
54              if (fcntl (0, F_DUPFD, -1) != -1) result |= 1;
55              if (errno != EINVAL) result |= 2;
56              if (fcntl (0, F_DUPFD, bad_fd) != -1) result |= 4;
57              if (errno != EINVAL) result |= 8;
58              /* On OS/2 kLIBC, F_DUPFD does not work on a directory fd */
59              {
60                int fd;
61                fd = open (".", O_RDONLY);
62                if (fd == -1)
63                  result |= 16;
64                else if (fcntl (fd, F_DUPFD, STDERR_FILENO + 1) == -1)
65                  result |= 32;
66
67                close (fd);
68              }
69              return result;]])],
70         [gl_cv_func_fcntl_f_dupfd_works=yes],
71         [gl_cv_func_fcntl_f_dupfd_works=no],
72         [case $host_os in
73            aix* | cygwin* | haiku*)
74               gl_cv_func_fcntl_f_dupfd_works="guessing no" ;;
75            *) gl_cv_func_fcntl_f_dupfd_works="guessing yes" ;;
76          esac])])
77    case $gl_cv_func_fcntl_f_dupfd_works in
78      *yes) ;;
79      *) gl_REPLACE_FCNTL
80        AC_DEFINE([FCNTL_DUPFD_BUGGY], [1], [Define this to 1 if F_DUPFD
81          behavior does not match POSIX]) ;;
82    esac
83
84    dnl Many systems lack F_DUPFD_CLOEXEC.
85    dnl NetBSD 9.0 declares F_DUPFD_CLOEXEC but it works only like F_DUPFD.
86    AC_CACHE_CHECK([whether fcntl understands F_DUPFD_CLOEXEC],
87      [gl_cv_func_fcntl_f_dupfd_cloexec],
88      [AC_RUN_IFELSE(
89         [AC_LANG_SOURCE(
90            [[#include <fcntl.h>
91              #include <unistd.h>
92              int main (int argc, char *argv[])
93              {
94                if (argc == 1)
95                  /* parent process */
96                  {
97                    if (fcntl (1, F_DUPFD_CLOEXEC, 10) < 0)
98                      return 1;
99                    return execl ("./conftest", "./conftest", "child", NULL);
100                  }
101                else
102                  /* child process */
103                  return (fcntl (10, F_GETFL) < 0 ? 0 : 42);
104              }
105            ]])
106         ],
107         [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
108#ifdef __linux__
109/* The Linux kernel only added F_DUPFD_CLOEXEC in 2.6.24, so we always replace
110   it to support the semantics on older kernels that failed with EINVAL.  */
111choke me
112#endif
113           ]])],
114           [gl_cv_func_fcntl_f_dupfd_cloexec=yes],
115           [gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])
116         ],
117         [gl_cv_func_fcntl_f_dupfd_cloexec=no],
118         [case "$host_os" in
119                     # Guess no on NetBSD.
120            netbsd*) gl_cv_func_fcntl_f_dupfd_cloexec="guessing no" ;;
121            *)       gl_cv_func_fcntl_f_dupfd_cloexec="$gl_cross_guess_normal" ;;
122          esac
123         ])
124      ])
125    case "$gl_cv_func_fcntl_f_dupfd_cloexec" in
126      *yes) ;;
127      *)    gl_REPLACE_FCNTL
128            dnl No witness macro needed for this bug.
129            ;;
130    esac
131  fi
132  dnl Replace fcntl() for supporting the gnulib-defined fchdir() function,
133  dnl to keep fchdir's bookkeeping up-to-date.
134  m4_ifdef([gl_FUNC_FCHDIR], [
135    gl_TEST_FCHDIR
136    if test $HAVE_FCHDIR = 0; then
137      gl_REPLACE_FCNTL
138    fi
139  ])
140])
141
142AC_DEFUN([gl_REPLACE_FCNTL],
143[
144  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
145  AC_CHECK_FUNCS_ONCE([fcntl])
146  if test $ac_cv_func_fcntl = no; then
147    HAVE_FCNTL=0
148  else
149    REPLACE_FCNTL=1
150  fi
151])
152