[usocket-devel] SBCL wait-for-input bug on attempt at second connection

[Chun Tian (binghe)]

Hi, Elliott

I believe this bug was now fixed.  The third WAIT-FOR-INPUT in your test code shouldn't return a non-NIL value, but a bug in function WAIT-FOR-INPUT caused the "last" status of sockets didn't been reset correctly.

This bug only affect SBCL and ECL on Windows, and was fixed in r653 on USOCKET 0.5.x branch [1].

Please update your USOCKET and confirm if it works for you (and report back, if possible), and I'll see your another bug report in a moment.

Regards,

Chun Tian (binghe)

P. S. Your test code also let me find a bug in LispWorks' version of SOCKET-ACCEPT, and I've done a fix based on completely different theory. Thanks.

[1] svn://common-lisp.net/project/usocket/svn/usocket/branches/0.5.x

在 2011-4-25，09:17， Elliott Slaughter 写道：

> First, the documentation for wait-for-input says that only integer are accepted, but code seems to think reals should work. (Tested on SBCL/Windows.)
> 
> Second, I have found a bug in wait-for-input in SBCL on Windows. The problem is that a wait-for-input on a TCP server socket which has already accepted one client will continue to return that the socket is ready to accept more clients even though it isn't, and thus cause an error when I try to call socket-accept. Here is the code that breaks it:
> 
> (defvar *port* 12345)
> (defvar *socket-server-listen*
>   (socket-listen *wildcard-host* *port* :element-type '(unsigned-byte 8)))
> 
> (defvar *socket-server-connection*)
> (setf
>  *socket-server-connection*
>  (when (wait-for-input *socket-server-listen* :timeout 0 :ready-only t)
>    (socket-accept *socket-server-listen*)))
> (format t "First time (before client connects) is ~s.~%"
>         *socket-server-connection*)
> 
> (defvar *socket-client-connection*)
> (setf *socket-client-connection*
>       (socket-connect "localhost" *port* :protocol :stream
>                       :element-type '(unsigned-byte 8) :timeout 0))
> 
> (setf
>  *socket-server-connection*
>  (when (wait-for-input *socket-server-listen* :timeout 0 :ready-only t)
>    (socket-accept *socket-server-listen*)))
> (format t "Second time (after client connects) is ~s.~%"
>         *socket-server-connection*)
> 
> (setf
>  *socket-server-connection*
>  (when (wait-for-input *socket-server-listen* :timeout 0 :ready-only t)
>    (socket-accept *socket-server-listen*)))
> (format t "Third time (before second client) is ~s.~%"
>         *socket-server-connection*)
> 
> The output on Windows/SBCL looks like:
> 
> First time (before client connects) is NIL.
> Second time (after client connects) is #<STREAM-USOCKET {24757F91}>.
> 
> It doesn't get to the first format call, because it hits the following error first:
> 
> Condition BAD-FILE-DESCRIPTOR-ERROR was signalled.
>    [Condition of type BAD-FILE-DESCRIPTOR-ERROR]
> 
> Restarts:
>  0: [RETRY] Retry SLIME REPL evaluation request.
>  1: [ABORT] Return to SLIME's top level.
>  2: [ABORT] Abort
>  3: [CLOSE-CONNECTION] Close SLIME connection
>  4: [ABORT] Exit debugger, returning to top level.
> 
> Backtrace:
>   0: (USOCKET::HANDLE-CONDITION #<SB-BSD-SOCKETS:SOCKET-ERROR {2475C889}> #<STREAM-SERVER-USOCKET {256F7C19}>)
>   1: (SIGNAL #<SB-BSD-SOCKETS:SOCKET-ERROR {2475C889}>)
>   2: (ERROR SB-BSD-SOCKETS:SOCKET-ERROR :ERRNO 9 :SYSCALL "accept")
>   3: (SB-BSD-SOCKETS:SOCKET-ERROR "accept")
>   4: ((SB-PCL::FAST-METHOD SB-BSD-SOCKETS:SOCKET-ACCEPT (SB-BSD-SOCKETS:SOCKET)) #<unavailable argument> #<unavailable argument> #<SB-BSD-SOCKETS:INET-SOCKET 0.0.0.0:12345, fd: 6 {2576DD91}>)
>   5: ((SB-PCL::FAST-METHOD SOCKET-ACCEPT (STREAM-SERVER-USOCKET)) #<unused argument> #<unused argument> #<STREAM-SERVER-USOCKET {256F7C19}> :ELEMENT-TYPE NIL)
>   6: (SB-INT:SIMPLE-EVAL-IN-LEXENV (SOCKET-ACCEPT *SOCKET-SERVER-LISTEN*) #<NULL-LEXENV>)
>   7: (SB-INT:SIMPLE-EVAL-IN-LEXENV (PROGN (SOCKET-ACCEPT *SOCKET-SERVER-LISTEN*)) #<NULL-LEXENV>)
>   8: (SB-INT:SIMPLE-EVAL-IN-LEXENV (WHEN (WAIT-FOR-INPUT *SOCKET-SERVER-LISTEN* :TIMEOUT 0 :READY-ONLY T) (SOCKET-ACCEPT *SOCKET-SERVER-LISTEN*)) #<NULL-LEXENV>)
>   9: (SB-INT:SIMPLE-EVAL-IN-LEXENV (SETF *SOCKET-SERVER-CONNECTION* (WHEN # #)) #<NULL-LEXENV>)
> 
> -- 
> Elliott Slaughter
> 
> "Don't worry about what anybody else is going to do. The best way to predict the future is to invent it." - Alan Kay
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