From bd52dcf0bce4470a04e2ec1592cc7e943ad4a2ab Mon Sep 17 00:00:00 2001
From: "hyunghwan.chung" <hyunghwan.chung@c9d47f8d-4fed-4a2f-8cad-691f5fbe3904>
Date: Mon, 7 May 2018 17:22:04 +0000
Subject: [PATCH] added extra checks for socket accept

---
 moo/kernel/Socket.moo |  3 +--
 moo/mod/sck.c         | 22 +++++++++++++++++++---
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/moo/kernel/Socket.moo b/moo/kernel/Socket.moo
index 38d73ca..8fe7036 100644
--- a/moo/kernel/Socket.moo
+++ b/moo/kernel/Socket.moo
@@ -493,7 +493,7 @@ class ServerSocket(Socket)
 			| cliaddr clisck cliact |
 			cliaddr := SocketAddress new.
 			clisck := self _accept: cliaddr.
-			if (clisck notError)
+			if (clisck notNil)
 			{
 				## the _accept method doesn't invoke the initialize method.
 				## i should invoke it manually here.
@@ -506,7 +506,6 @@ class ServerSocket(Socket)
 					clisck beWatched.
 				}
 				else { clisck close }.
-	
 			}.
 		].
 	}
diff --git a/moo/mod/sck.c b/moo/mod/sck.c
index 64c1527..87d8f88 100644
--- a/moo/mod/sck.c
+++ b/moo/mod/sck.c
@@ -218,22 +218,38 @@ static moo_pfrc_t pf_accept_socket (moo_t* moo, moo_mod_t* mod, moo_ooi_t nargs)
 	newfd = accept4(fd, (struct sockaddr*)MOO_OBJ_GET_BYTE_SLOT(arg), &addrlen, SOCK_NONBLOCK | SOCK_CLOEXEC);
 	if (newfd == -1)
 	{
-		if (errno != ENOSYS) 
+		if (errno == ENOSYS) goto normal_accept;
+		
+		if (errno != EWOULDBLOCK && errno != EAGAIN) 
 		{
 			moo_seterrwithsyserr (moo, errno);
 			return MOO_PF_FAILURE;
 		}
+
+		/* return nil if accept() is not ready to accept a socket */
+		MOO_STACK_SETRET (moo, nargs, moo->_nil);
+		return MOO_PF_SUCCESS;
 	}
 	else
 	{
 		goto accept_done;
 	}
+normal_accept:
 #endif
+
 	newfd = accept(fd, (struct sockaddr*)MOO_OBJ_GET_BYTE_SLOT(arg), &addrlen);
 	if (newfd == -1)
 	{
-		moo_seterrwithsyserr (moo, errno);
-		return MOO_PF_FAILURE;
+		if (errno != EWOULDBLOCK && errno != EAGAIN)
+		{
+			moo_seterrwithsyserr (moo, errno);
+			return MOO_PF_FAILURE;
+		}
+
+
+		/* return nil if accept() is not ready to accept a socket */
+		MOO_STACK_SETRET (moo, nargs, moo->_nil);
+		return MOO_PF_SUCCESS;
 	}
 	fl = fcntl(newfd, F_GETFL, 0);
 	if (fl == -1)