IO: Detect closed IO when resuming readable/writable event

spec/std/io/io_spec.cr

@@ -828,7 +828,7 @@ describe IO do
         ch = Channel(Symbol).new(1)
 
         IO.pipe do |read, write|
-          spawn do
+          f = spawn do
             ch.send :start
             read.gets
           rescue
@@ -838,6 +838,10 @@ describe IO do
           delay(1) { ch.send :timeout }
 
           ch.receive.should eq(:start)
+          while f.running?
+            # Wait until the fiber is blocked
+            Fiber.yield
+          end
           read.close
           ch.receive.should eq(:end)
         end

spec/std/socket/udp_socket_spec.cr

@@ -108,7 +108,7 @@ describe UDPSocket do
           sleep 100.milliseconds
           udp.close
         end
-        expect_raises_errno(Errno::EBADF, "Error receiving datagram: Bad file descriptor") { udp.receive }
+        expect_raises(IO::Error, "Closed stream") { udp.receive }
       end
     end
   end

src/crystal/system/file.cr

@@ -40,6 +40,13 @@ module Crystal::System::File
 
     oflag = m | o
   end
+
+  # Closes the internal file descriptor without notifying libevent.
+  # This is directly used after the fork of a process to close the
+  # parent's Crystal::Signal.@@pipe reference before re initializing
+  # the event loop. In the case of a fork that will exec there is even
+  # no need to initialize the event loop at all.
+  # def file_description_close
 end
 
 {% if flag?(:unix) %}

src/crystal/system/unix/file_descriptor.cr

@@ -110,6 +110,15 @@ module Crystal::System::FileDescriptor
   end
 
   private def system_close
+    # Perform libevent cleanup before LibC.close.
+    # Using a file descriptor after it has been closed is never defined and can
+    # always lead to undefined results. This is not specific to libevent.
+    evented_close
+
+    file_description_close
+  end
+
+  def file_description_close
     if LibC.close(@fd) != 0
       case Errno.value
       when Errno::EINTR, Errno::EINPROGRESS
@@ -118,8 +127,6 @@ module Crystal::System::FileDescriptor
         raise Errno.new("Error closing file")
       end
     end
-  ensure
-    evented_close
   end
 
   def self.pipe(read_blocking, write_blocking)

src/crystal/system/win32/file_descriptor.cr

@@ -114,6 +114,10 @@ module Crystal::System::FileDescriptor
   end
 
   private def system_close
+    file_description_close
+  end
+
+  def file_description_close
     err = nil
     if LibC._close(@fd) != 0
       case Errno.value

src/io/evented.cr

@@ -131,6 +131,8 @@ module IO::Evented
       @read_timed_out = false
       yield Timeout.new("Read timed out")
     end
+
+    check_open
   end
 
   private def add_read_event(timeout = @read_timeout) : Nil
@@ -154,6 +156,8 @@ module IO::Evented
       @write_timed_out = false
       yield Timeout.new("Write timed out")
     end
+
+    check_open
   end
 
   private def add_write_event(timeout = @write_timeout) : Nil

src/io/file_descriptor.cr

@@ -177,7 +177,11 @@ class IO::FileDescriptor < IO
   private def unbuffered_close
     return if @closed
 
-    system_close ensure @closed = true
+    # Set before the @closed state so the pending
+    # IO::Evented readers and writers can be cancelled
+    # knowing the IO is in a closed state.
+    @closed = true
+    system_close
   end
 
   private def unbuffered_flush

src/signal.cr

@@ -220,7 +220,7 @@ module Crystal::Signal
   # Replaces the signal pipe so the child process won't share the file
   # descriptors of the parent process and send it received signals.
   def self.after_fork
-    @@pipe.each(&.close)
+    @@pipe.each(&.file_description_close)
   ensure
     @@pipe = IO.pipe(read_blocking: false, write_blocking: true)
   end
@@ -243,7 +243,7 @@ module Crystal::Signal
     end
   ensure
     {% unless flag?(:preview_mt) %}
-      @@pipe.each(&.close)
+      @@pipe.each(&.file_description_close)
     {% end %}
   end
 

src/socket.cr

@@ -250,7 +250,7 @@ class Socket < IO
         if closed?
           return
         elsif Errno.value == Errno::EAGAIN
-          wait_readable
+          wait_readable rescue nil
         else
           raise Errno.new("accept")
         end
@@ -556,6 +556,12 @@ class Socket < IO
   private def unbuffered_close
     return if @closed
 
+    # Perform libevent cleanup before LibC.close.
+    # Using a file descriptor after it has been closed is never defined and can
+    # always lead to undefined results. This is not specific to libevent.
+    @closed = true
+    evented_close
+
     err = nil
     if LibC.close(@fd) != 0
       case Errno.value
@@ -566,9 +572,6 @@ class Socket < IO
       end
     end
 
-    @closed = true
-    evented_close
-
     raise err if err
   end