Process#exec: set close-on-exec to false for fd redirection

CHANGELOG.md

@@ -20,6 +20,7 @@ Bug fixes:
 * Don't clone methods when setting method to the same visibility (#1794, @XrXr).
 * BigDecimal() deal with large rationals precisely (#1797, @XrXr).
 * Make it possible to call `instance_exec` with `rb_block_call` (#1802, @XrXr).
+* Process#exec: set close-on-exec to false for fd redirection (#1805, @XrXr, @rafaelfranca).
 
 Compatibility:
 

spec/ruby/core/process/exec_spec.rb

@@ -212,6 +212,35 @@
 
           File.read(@name).should == "writing to fd: #{child_fd}"
         end
+
+        it "lets the process after exec have specified file descriptor dispite close_on_exec" do
+          map_fd_fixture = fixture __FILE__, "map_fd.rb"
+          cmd = <<-EOC
+            f = File.open('#{@name}', 'w+')
+            puts(f.fileno, f.close_on_exec?)
+            STDOUT.flush
+            Process.exec("#{ruby_cmd(map_fd_fixture)} \#{f.fileno}", f.fileno => f.fileno)
+            EOC
+
+          output = ruby_exe(cmd, escape: true)
+          child_fd, close_on_exec = output.split
+
+          child_fd.to_i.should > STDERR.fileno
+          close_on_exec.should == 'true'
+          File.read(@name).should == "writing to fd: #{child_fd}"
+        end
+
+        it "sets close_on_exec to false on specified fd even when it fails" do
+          cmd = <<-EOC
+            f = File.open('#{__FILE__}', 'r')
+            puts(f.close_on_exec?)
+            Process.exec('/', f.fileno => f.fileno) rescue
+            puts(f.close_on_exec?)
+            EOC
+
+          output = ruby_exe(cmd, escape: true)
+          output.split.should == ['true', 'false']
+        end
       end
     end
   end

spec/tags/core/process/exec_tags.txt

@@ -18,3 +18,5 @@ slow:Process.exec with a command array uses the first element as the command nam
 slow:Process.exec with a command array coerces the argument using to_ary
 slow:Process.exec with a command array raises an ArgumentError if the Array does not have exactly two elements
 slow:Process.exec with an options Hash with Integer option keys maps the key to a file descriptor in the child that inherits the file descriptor from the parent specified by the value
+slow:Process.exec with an options Hash with Integer option keys lets the process after exec have specified file descriptor dispite close_on_exec
+slow:Process.exec with an options Hash with Integer option keys sets close_on_exec to false on specified fd even when it fails

src/main/ruby/truffleruby/core/truffle/process_operations.rb

@@ -402,7 +402,7 @@ def spawn_setup(alter_process)
 
           if redirect_fd = @options[:redirect_fd]
             redirect_fd.each_slice(2) do |from, to|
-              redirect_file_descriptor(from, to)
+              redirect_file_descriptor(from, to, alter_process)
             end
           end
         end
@@ -415,9 +415,14 @@ def safe_close_on_exec?(fd)
         (flags & File::FD_CLOEXEC) != 0
       end
 
-      def redirect_file_descriptor(from, to)
+      def redirect_file_descriptor(from, to, alter_process)
         to = (-to + 1) if to < 0
-
+        if alter_process && from == to
+          flags = Truffle::POSIX.fcntl(from, File::F_GETFD, 0)
+          unless flags < 0 || flags & File::FD_CLOEXEC == 0
+            Truffle::POSIX.fcntl(from, File::F_SETFD, flags ^ File::FD_CLOEXEC)
+          end
+        end
         result = Truffle::POSIX.dup2(to, from)
         Errno.handle if result < 0
       end