Re: Problem with netcat

[Detlev Zundel]

Hi John,

> Attached is the output of two strace runs.
> strace.netcat is of 'strace -r guile --listen=9000' with 'netcat localhost
> 9000 < a.ss' run against it.
> strace.interactive is of 'strace -r guile --listen=9000' with 'netcat
> localhost 9000' used to access it and me manually typing (+ 5 3) then
> hitting <ctrl>-d in both windows to terminate.
>
> Thanks Andy and Detlev.

Thanks for the input - I think the problem is clear to see here:

>      0.000033 rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0
>      0.000039 write(90, "scheme@(guile-user)> ", 21scheme@(guile-user)> ) = 21
>      0.000028 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
>      0.000022 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
>      0.000032 read(0,  <unfinished ...>
>     30.150227 +++ killed by SIGPIPE +++

This is from the problematic log.  It turns out that an "strace -f"
would have be better advice for you so we would have seen the actual
socket process but funnily enough I now sometimes can regenerate the
error (usually by pressing C-c in netcat).

This is the last I see for such a case:

[pid   706] times({tms_utime=26, tms_stime=3, tms_cutime=0, tms_cstime=0}) = 
-1349846525
[pid   706] select(1024, [81], [], [], {0, 0}) = 0 (Timeout)
[pid   706] brk(0x9353000)              = 0x9353000
[pid   706] brk(0x934b000)              = 0x934b000
[pid   706] write(81, "scheme@(guile-user) [1]> ", 25) = 25
[pid   706] read(81, "", 1)             = 0
[pid   706] write(81, "\n", 1)          = 1
[pid   706] select(1024, [81], [], [], {0, 0}) = 1 (in [81], left {0, 0})
[pid   706] read(81, "", 1)             = 0
[pid   706] select(1024, [81], [], [], {0, 0}) = 1 (in [81], left {0, 0})
[pid   706] read(81, "", 1)             = 0
[pid   706] write(81, "\n", 1)          = -1 EPIPE (Broken pipe)
[pid   706] --- SIGPIPE (Broken pipe) @ 0 (0) ---
Process 706 detached
[pid 32521] +++ killed by SIGPIPE +++
[pid 32520] +++ killed by SIGPIPE +++
+++ killed by SIGPIPE +++

So it seems like guile wants simply to output a newline but the socket
is closed already and the process then gets the SIGPIPE signal which
guile is not prepared for.

I will need to dig deeper into the innards of guile to find an answer on
how to prevent that.  If someone beats me to it I'll still be happy ;)

Cheers
  Detlev

-- 
Number theorists do it perfectly and rationally.