Unix(macOS) SocketPlugin:

Fix sendDone/primtiveSocketSendDone/sqSocketSendDone on macOS.  The select in
socketWritable does not answer true for writable sockets, presumably because
the select in aioPoll already has done.  So have dataHandler (which is called
from aioPoll when the socket *is* writable) set a flag in privateSocketStruct
notifiedOfWritability and use this to avoid the wrongly unsuccessful call of
select in sqSocketSendDone. Clear notifiedOfWritability before any and all send/
write system calls.
Have sqWin32NewNet.c process the select result in its socketWritable in exactly
the same way as sqUnixSocket.c's.

I WELCOME ANY REVIEW OF THIS COMMIT!!  Levente, Tobias, you might take a close
look at this one.

Author: eliotmiranda

platforms/unix/plugins/SocketPlugin/sqUnixSocket.c

@@ -165,18 +165,19 @@ union sockaddr_any
 
 typedef struct privateSocketStruct
 {
-  int s;			/* Unix socket */
-  int connSema;			/* connection io notification semaphore */
-  int readSema;			/* read io notification semaphore */
-  int writeSema;		/* write io notification semaphore */
-  int sockState;		/* connection + data state */
-  int sockError;		/* errno after socket error */
+  int s;					/* Unix socket */
+  int connSema;				/* connection io notification semaphore */
+  int readSema;				/* read io notification semaphore */
+  int writeSema;			/* write io notification semaphore */
+  int sockState;			/* connection + data state */
+  int sockError;			/* errno after socket error */
   union sockaddr_any peer;	/* default send/recv address for UDP */
   socklen_t peerSize;		/* dynamic sizeof(peer) */
-  union sockaddr_any sender;	/* sender address for last UDP receive */
+  union sockaddr_any sender;/* sender address for last UDP receive */
   socklen_t senderSize;		/* dynamic sizeof(sender) */
-  int multiListen;		/* whether to listen for multiple connections */
-  int acceptedSock;		/* a connection that has been accepted */
+  int multiListen;			/* whether to listen for multiple connections */
+  int acceptedSock;			/* a connection that has been accepted */
+  int notifiedOfWritability; /* flag compensates for select denying writable */
 } privateSocketStruct;
 
 #define CONN_NOTIFY		(1<<0)
@@ -343,12 +344,20 @@ socketReadable(int s)
 static int
 socketWritable(int s)
 {
-  struct timeval tv= { 0, 0 };
+  struct timeval tv = { 0, 0 }; // i.e. poll
   fd_set fds;
 
   FD_ZERO(&fds);
   FD_SET(s, &fds);
-  return select(s+1, 0, &fds, 0, &tv) > 0;
+#ifdef AIO_DEBUG
+  { int r = select(1, 0, &fds, 0, &tv);
+	if (r < 0)
+		perror("socketWritable: select(1,0,&fd,0,&poll)");
+	return r > 0;
+  }
+#else
+  return select(1, 0, &fds, 0, &tv) > 0;
+#endif
 }
 
 /* answer the error condition on the given socket */
@@ -488,7 +497,14 @@ dataHandler(int fd, void *data, int flags)
 	  }
 	  notify(pss, READ_NOTIFY);
 	}
-  if (flags & AIO_W) notify(pss, WRITE_NOTIFY);
+  if (flags & AIO_W) {
+	notify(pss, WRITE_NOTIFY);
+	/* in socketWritable select may answer zero for writable sockets, resulting
+	 * in sqSocketSendDone answering false for new sockets. So we subvert select
+	 * by setting the notifiedOfWritability flag, tested in sqSocketSendDone.
+	 */
+	pss->notifiedOfWritability = true;
+  }
   if (flags & AIO_X)
 	{
 	  /* assume out-of-band data has arrived */
@@ -1120,16 +1136,23 @@ sqSocketReceiveDataAvailable(SocketPtr s)
 }
 
 
-/* answer whether the socket has space to receive more data */
+/* answer whether the socket has space to send more data */
 
 sqInt
 sqSocketSendDone(SocketPtr s)
 {
-  if (!socketValid(s))
-	return false;
-  if (SOCKETSTATE(s) == Connected)
-	{
-	  if (socketWritable(SOCKET(s))) return true;
+  if (socketValid(s)
+   && SOCKETSTATE(s) == Connected)
+	{
+	/* in socketWritable select may answer zero for writable sockets, resulting
+	 * in sqSocketSendDone answering false for new sockets. So we subvert select
+	 * by testing the notifiedOfWritability flag, set in dataHandler.
+	 */
+	  if (PSP(s)->notifiedOfWritability)
+		return true;
+	  if (socketWritable(SOCKET(s)))
+		return true;
+	  FPRINTF((stderr, "sqSocketSendDone(%d) !socketWritable\n", SOCKET(s)));
 	  aioHandle(SOCKET(s), dataHandler, AIO_WX);
 	}
   return false;
@@ -1202,6 +1225,7 @@ sqSocketSendDataBufCount(SocketPtr s, char *buf, sqInt bufSize)
   if (!socketValid(s))
 	return -1;
 
+  PSP(s)->notifiedOfWritability = false;
   if (TCPSocketType != s->socketType)
 	{
 	  /* --- UDP/RAW --- */
@@ -1291,6 +1315,7 @@ sqSockettoHostportSendDataBufCount(SocketPtr s, sqInt address, sqInt port, char
 	  saddr.sin_family= AF_INET;
 	  saddr.sin_port= htons((short)port);
 	  saddr.sin_addr.s_addr= htonl(address);
+	  PSP(s)->notifiedOfWritability = false;
 	  {
 		int nsent= sendto(SOCKET(s), buf, bufSize, 0, (struct sockaddr *)&saddr, sizeof(saddr));
 		if (nsent >= 0)
@@ -2348,6 +2373,7 @@ sqSocketSendUDPToSizeDataBufCount(SocketPtr s, char *addr, sqInt addrSize, char
   if (socketValid(s) && addressValid(addr, addrSize) && (TCPSocketType != s->socketType)) /* --- UDP/RAW --- */
 	{
 	  int nsent= sendto(SOCKET(s), buf, bufSize, 0, socketAddress(addr), addrSize - AddressHeaderSize);
+	  PSP(s)->notifiedOfWritability = false;
 	  if (nsent >= 0)
 		return nsent;
 

platforms/win32/plugins/SocketPlugin/sqWin32NewNet.c

@@ -186,12 +186,12 @@ static int socketReadable(SOCKET s)
 
 static int socketWritable(SOCKET s)
 {
-  struct timeval tv= { 0, 0 };
+  struct timeval tv = { 0, 0 }; // i.e. poll
   fd_set fds;
 
   FD_ZERO(&fds);
   FD_SET(s, &fds);
-  return select(1, NULL, &fds, NULL, &tv) == 1;
+  return select(1, NULL, &fds, NULL, &tv) > 0;
 }
 
 static int socketError(SOCKET s)