`accept' on nonblocking socket can return #f

* doc/ref/posix.texi (Network Sockets and Communication):
* libguile/socket.c (scm_accept): Return #f if the socket is nonblocking
  and no connection is ready.

doc/ref/posix.texi

@@ -3260,15 +3260,26 @@ The return value is unspecified.
 @deffn {Scheme Procedure} accept sock
 @deffnx {C Function} scm_accept (sock)
 Accept a connection from socket port @var{sock} which has been enabled
-for listening with @code{listen} above.  If there are no incoming
+for listening with @code{listen} above.
-connections in the queue, wait until one is available (unless
+
-@code{O_NONBLOCK} has been set on the socket, @pxref{Ports and File
+If there are no incoming connections in the queue, there are two
-Descriptors,@code{fcntl}}).
+possible behaviors, depending on whether @var{sock} has been configured
+for non-blocking operation or not:
+
+@itemize
+@item
+If there is no connection waiting and the socket was set to non-blocking
+mode with the @code{O_NONBLOCK} port option (@pxref{Ports and File
+Descriptors,@code{fcntl}}), return @code{#f} directly.
+
+@item
+Otherwise wait until a connection is available.
+@end itemize
 
 The return value is a pair.  The @code{car} is a new socket port,
-connected and ready to communicate.  The @code{cdr} is a socket
+connected and ready to communicate.  The @code{cdr} is a socket address
-address object (@pxref{Network Socket Address}) which is where the
+object (@pxref{Network Socket Address}) which is where the remote
-remote connection is from (like @code{getpeername} below).
+connection is from (like @code{getpeername} below).
 
 All communication takes place using the new socket returned.  The
 given @var{sock} remains bound and listening, and @code{accept} may be

libguile/socket.c

@@ -1236,16 +1236,15 @@ SCM_DEFINE (scm_make_socket_address, "make-socket-address", 2, 0, 1,
 
 SCM_DEFINE (scm_accept, "accept", 1, 0, 0, 
             (SCM sock),
-	    "Accept a connection on a bound, listening socket.\n"
+	    "Accept a connection on a bound, listening socket.  If there\n"
-	    "If there\n"
+	    "are no pending connections in the queue, there are two\n"
-	    "are no pending connections in the queue, wait until\n"
+            "possibilities: if the socket has been configured as\n"
-	    "one is available unless the non-blocking option has been\n"
+            "non-blocking, return @code{#f} directly.  Otherwise wait\n"
-	    "set on the socket.\n\n"
+            "until a connection is available.  When a connection comes,\n"
-	    "The return value is a\n"
+	    "the return value is a pair in which the @emph{car} is a new\n"
-	    "pair in which the @emph{car} is a new socket port for the\n"
+            "socket port for the connection and the @emph{cdr} is an\n"
-	    "connection and\n"
+            "object with address information about the client which\n"
-	    "the @emph{cdr} is an object with address information about the\n"
+            "initiated the connection.\n\n"
-	    "client which initiated the connection.\n\n"
 	    "@var{sock} does not become part of the\n"
 	    "connection and will continue to accept new requests.")
 #define FUNC_NAME s_scm_accept
@@ -1262,7 +1261,11 @@ SCM_DEFINE (scm_accept, "accept", 1, 0, 0,
   fd = SCM_FPORT_FDES (sock);
   SCM_SYSCALL (newfd = accept (fd, (struct sockaddr *) &addr, &addr_size));
   if (newfd == -1)
+    {
+      if (errno == EAGAIN || errno == EWOULDBLOCK)
+        return SCM_BOOL_F;
       SCM_SYSERROR;
+    }
   newsock = SCM_SOCK_FD_TO_PORT (newfd);
   address = _scm_from_sockaddr (&addr, addr_size,
 				FUNC_NAME);