1# fcntl-o.m4 serial 6 2dnl Copyright (C) 2006, 2009-2020 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 7dnl Written by Paul Eggert. 8 9AC_PREREQ([2.60]) 10 11# Test whether the flags O_NOATIME and O_NOFOLLOW actually work. 12# Define HAVE_WORKING_O_NOATIME to 1 if O_NOATIME works, or to 0 otherwise. 13# Define HAVE_WORKING_O_NOFOLLOW to 1 if O_NOFOLLOW works, or to 0 otherwise. 14AC_DEFUN([gl_FCNTL_O_FLAGS], 15[ 16 dnl Persuade glibc <fcntl.h> to define O_NOATIME and O_NOFOLLOW. 17 AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS]) 18 19 AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles 20 AC_CHECK_HEADERS_ONCE([unistd.h]) 21 AC_CHECK_FUNCS_ONCE([symlink]) 22 AC_CACHE_CHECK([for working fcntl.h], [gl_cv_header_working_fcntl_h], 23 [AC_RUN_IFELSE( 24 [AC_LANG_PROGRAM( 25 [[#include <sys/types.h> 26 #include <sys/stat.h> 27 #if HAVE_UNISTD_H 28 # include <unistd.h> 29 #else /* on Windows with MSVC */ 30 # include <io.h> 31 # include <stdlib.h> 32 # defined sleep(n) _sleep ((n) * 1000) 33 #endif 34 #include <fcntl.h> 35 #ifndef O_NOATIME 36 #define O_NOATIME 0 37 #endif 38 #ifndef O_NOFOLLOW 39 #define O_NOFOLLOW 0 40 #endif 41 static int const constants[] = 42 { 43 O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC, O_APPEND, 44 O_NONBLOCK, O_SYNC, O_ACCMODE, O_RDONLY, O_RDWR, O_WRONLY 45 }; 46 ]], 47 [[ 48 int result = !constants; 49 #if HAVE_SYMLINK 50 { 51 static char const sym[] = "conftest.sym"; 52 if (symlink ("/dev/null", sym) != 0) 53 result |= 2; 54 else 55 { 56 int fd = open (sym, O_WRONLY | O_NOFOLLOW | O_CREAT, 0); 57 if (fd >= 0) 58 { 59 close (fd); 60 result |= 4; 61 } 62 } 63 if (unlink (sym) != 0 || symlink (".", sym) != 0) 64 result |= 2; 65 else 66 { 67 int fd = open (sym, O_RDONLY | O_NOFOLLOW); 68 if (fd >= 0) 69 { 70 close (fd); 71 result |= 4; 72 } 73 } 74 unlink (sym); 75 } 76 #endif 77 { 78 static char const file[] = "confdefs.h"; 79 int fd = open (file, O_RDONLY | O_NOATIME); 80 if (fd < 0) 81 result |= 8; 82 else 83 { 84 struct stat st0; 85 if (fstat (fd, &st0) != 0) 86 result |= 16; 87 else 88 { 89 char c; 90 sleep (1); 91 if (read (fd, &c, 1) != 1) 92 result |= 24; 93 else 94 { 95 if (close (fd) != 0) 96 result |= 32; 97 else 98 { 99 struct stat st1; 100 if (stat (file, &st1) != 0) 101 result |= 40; 102 else 103 if (st0.st_atime != st1.st_atime) 104 result |= 64; 105 } 106 } 107 } 108 } 109 } 110 return result;]])], 111 [gl_cv_header_working_fcntl_h=yes], 112 [case $? in #( 113 4) gl_cv_header_working_fcntl_h='no (bad O_NOFOLLOW)';; #( 114 64) gl_cv_header_working_fcntl_h='no (bad O_NOATIME)';; #( 115 68) gl_cv_header_working_fcntl_h='no (bad O_NOATIME, O_NOFOLLOW)';; #( 116 *) gl_cv_header_working_fcntl_h='no';; 117 esac], 118 [case "$host_os" in 119 # Guess 'no' on native Windows. 120 mingw*) gl_cv_header_working_fcntl_h='no' ;; 121 *) gl_cv_header_working_fcntl_h=cross-compiling ;; 122 esac 123 ]) 124 ]) 125 126 case $gl_cv_header_working_fcntl_h in #( 127 *O_NOATIME* | no | cross-compiling) ac_val=0;; #( 128 *) ac_val=1;; 129 esac 130 AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOATIME], [$ac_val], 131 [Define to 1 if O_NOATIME works.]) 132 133 case $gl_cv_header_working_fcntl_h in #( 134 *O_NOFOLLOW* | no | cross-compiling) ac_val=0;; #( 135 *) ac_val=1;; 136 esac 137 AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOFOLLOW], [$ac_val], 138 [Define to 1 if O_NOFOLLOW works.]) 139]) 140