Use File::NULL instead of hard coded null device names

Merged: https://github.com/ruby/ruby/pull/8050

ext/extmk.rb

@@ -43,11 +43,7 @@ $" << "mkmf.rb"
 load File.expand_path("lib/mkmf.rb", srcdir)
 require 'optparse/shellwords'
 
-if defined?(File::NULL)
+@null = File::NULL
-  @null = File::NULL
-elsif !File.chardev?(@null = "/dev/null")
-  @null = "nul"
-end
 
 def verbose?
   $mflags.defined?("V") == "1"

file.c

@@ -4971,7 +4971,7 @@ rb_file_s_extname(VALUE klass, VALUE fname)
  *
  *  Returns the string representation of the path
  *
- *     File.path("/dev/null")          #=> "/dev/null"
+ *     File.path(File::NULL)           #=> "/dev/null"
  *     File.path(Pathname.new("/tmp")) #=> "/tmp"
  *
  */
@@ -6086,7 +6086,7 @@ rb_stat_z(VALUE obj)
  *  the file otherwise.
  *
  *     File.stat("testfile").size?   #=> 66
- *     File.stat("/dev/null").size?  #=> nil
+ *     File.stat(File::NULL).size?   #=> nil
  *
  */
 

io.c

@@ -5256,7 +5256,7 @@ rb_io_close_on_exec_p(VALUE io)
  *
  *  Sets a close-on-exec flag.
  *
- *     f = open("/dev/null")
+ *     f = File.open(File::NULL)
  *     f.close_on_exec = true
  *     system("cat", "/proc/self/fd/#{f.fileno}") # cat: /proc/self/fd/3: No such file or directory
  *     f.closed?                #=> false
@@ -9634,11 +9634,11 @@ rb_io_autoclose_p(VALUE io)
  *
  *  Sets auto-close flag.
  *
- *     f = open("/dev/null")
+ *     f = File.open(File::NULL)
  *     IO.for_fd(f.fileno).close
  *     f.gets # raises Errno::EBADF
  *
- *     f = open("/dev/null")
+ *     f = File.open(File::NULL)
  *     g = IO.for_fd(f.fileno)
  *     g.autoclose = false
  *     g.close

lib/mkmf.rb

@@ -2699,7 +2699,7 @@ MESSAGE
   when $mswin
     $nmake = ?m if /nmake/i =~ make
   end
-  $ignore_error = $nmake ? '' : ' 2> /dev/null || true'
+  $ignore_error = $nmake ? '' : " 2> #{File::NULL} || true"
 
   RbConfig::CONFIG["srcdir"] = CONFIG["srcdir"] =
     $srcdir = arg_config("--srcdir", File.dirname($0))

process.c

@@ -4804,11 +4804,11 @@ rb_f_system(int argc, VALUE *argv, VALUE _)
  *
  *  A filename can be specified as a hash value.
  *
- *    pid = spawn(command, :in=>"/dev/null") # read mode
+ *    pid = spawn(command, :in=>File::NULL) # read mode
- *    pid = spawn(command, :out=>"/dev/null") # write mode
+ *    pid = spawn(command, :out=>File::NULL) # write mode
  *    pid = spawn(command, :err=>"log") # write mode
- *    pid = spawn(command, [:out, :err]=>"/dev/null") # write mode
+ *    pid = spawn(command, [:out, :err]=>File::NULL) # write mode
- *    pid = spawn(command, 3=>"/dev/null") # read mode
+ *    pid = spawn(command, 3=>File::NULL) # read mode
  *
  *  For stdout and stderr (and combination of them),
  *  it is opened in write mode.
@@ -6834,7 +6834,7 @@ static int rb_daemon(int nochdir, int noclose);
  *  nochdir is true (i.e. non false), it changes the current
  *  working directory to the root ("/"). Unless the argument
  *  noclose is true, daemon() will redirect standard input,
- *  standard output and standard error to /dev/null.
+ *  standard output and standard error to null device.
  *  Return zero on success, or raise one of Errno::*.
  */
 
@@ -6854,6 +6854,8 @@ proc_daemon(int argc, VALUE *argv, VALUE _)
     return INT2FIX(n);
 }
 
+extern const char ruby_null_device[];
+
 static int
 rb_daemon(int nochdir, int noclose)
 {
@@ -6877,7 +6879,7 @@ rb_daemon(int nochdir, int noclose)
     if (!nochdir)
         err = chdir("/");
 
-    if (!noclose && (n = rb_cloexec_open("/dev/null", O_RDWR, 0)) != -1) {
+    if (!noclose && (n = rb_cloexec_open(ruby_null_device, O_RDWR, 0)) != -1) {
         rb_update_max_fd(n);
         (void)dup2(n, 0);
         (void)dup2(n, 1);

test/ruby/test_file_exhaustive.rb

@@ -1518,7 +1518,7 @@ class TestFileExhaustive < Test::Unit::TestCase
 
       stat = File.stat(f)
       unless stat.chardev?
-        # /dev/null may be accessed by other processes
+        # null device may be accessed by other processes
         assert_equal(stat.atime, File.atime(f), f)
         assert_equal(stat.ctime, File.ctime(f), f)
         assert_equal(stat.mtime, File.mtime(f), f)

tool/lib/vcs.rb

@@ -154,8 +154,7 @@ class VCS
   alias dryrun? dryrun
   alias debug? debug
 
-  NullDevice = defined?(IO::NULL) ? IO::NULL :
+  NullDevice = IO::NULL
-    %w[/dev/null NUL NIL: NL:].find {|dev| File.exist?(dev)}
 
   # returns
   # * the last revision of the current branch