code.delx.au - gnu-emacs/blob - m4/fcntl.m4

   1 # fcntl.m4 serial 8
   2 dnl Copyright (C) 2009-2016 Free Software Foundation, Inc.
   3 dnl This file is free software; the Free Software Foundation
   4 dnl gives unlimited permission to copy and/or distribute it,
   5 dnl 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
  16 AC_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               return result;]])],
  58          [gl_cv_func_fcntl_f_dupfd_works=yes],
  59          [gl_cv_func_fcntl_f_dupfd_works=no],
  60          [case $host_os in
  61             aix* | cygwin* | haiku*)
  62                gl_cv_func_fcntl_f_dupfd_works="guessing no" ;;
  63             *) gl_cv_func_fcntl_f_dupfd_works="guessing yes" ;;
  64           esac])])
  65     case $gl_cv_func_fcntl_f_dupfd_works in
  66       *yes) ;;
  67       *) gl_REPLACE_FCNTL
  68         AC_DEFINE([FCNTL_DUPFD_BUGGY], [1], [Define this to 1 if F_DUPFD
  69           behavior does not match POSIX]) ;;
  70     esac
  71
  72     dnl Many systems lack F_DUPFD_CLOEXEC
  73     AC_CACHE_CHECK([whether fcntl understands F_DUPFD_CLOEXEC],
  74       [gl_cv_func_fcntl_f_dupfd_cloexec],
  75       [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
  76 #include <fcntl.h>
  77 #ifndef F_DUPFD_CLOEXEC
  78 choke me
  79 #endif
  80          ]])],
  81          [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
  82 #ifdef __linux__
  83 /* The Linux kernel only added F_DUPFD_CLOEXEC in 2.6.24, so we always replace
  84    it to support the semantics on older kernels that failed with EINVAL.  */
  85 choke me
  86 #endif
  87            ]])],
  88            [gl_cv_func_fcntl_f_dupfd_cloexec=yes],
  89            [gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])],
  90          [gl_cv_func_fcntl_f_dupfd_cloexec=no])])
  91     if test "$gl_cv_func_fcntl_f_dupfd_cloexec" != yes; then
  92       gl_REPLACE_FCNTL
  93       dnl No witness macro needed for this bug.
  94     fi
  95   fi
  96   dnl Replace fcntl() for supporting the gnulib-defined fchdir() function,
  97   dnl to keep fchdir's bookkeeping up-to-date.
  98   m4_ifdef([gl_FUNC_FCHDIR], [
  99     gl_TEST_FCHDIR
 100     if test $HAVE_FCHDIR = 0; then
 101       gl_REPLACE_FCNTL
 102     fi
 103   ])
 104 ])
 105
 106 AC_DEFUN([gl_REPLACE_FCNTL],
 107 [
 108   AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
 109   AC_CHECK_FUNCS_ONCE([fcntl])
 110   if test $ac_cv_func_fcntl = no; then
 111     HAVE_FCNTL=0
 112   else
 113     REPLACE_FCNTL=1
 114   fi
 115 ])