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

[Elliott Slaughter]

By the way (in case you have any trouble reproducing), the version of SBCL
used to test this can be obtained here. (It's just a more up-to-date version
than what you can get on the SBCL download page that I compiled myself.

http://elliottslaughter.net/files/sbcl-1.0.46.msi

2011/4/30 Chun Tian (binghe) <binghe.lisp at gmail.com>

> Hi, Elliott
>
> Sorry for late responses, I'm a little busy in the past week.
>
> It seems that current implementation of WAIT-FOR-INPUT on SBCL/Windows have
> some bugs, I'll look into it in next two days and try to fix it.  Whatever
> bug it has, it shuold NOT be any bug in SBCL itself, because this function
> was completely written using SB-ALIEN and underlying Win32 API.
>
> I'll put your code as part of usocket's unit test and see if it also
> affects other backends.
>
> Regards,
>
> Chun Tian (binghe)
>
> 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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>
>
>


-- 
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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