bug#13018: fport_fill_input should handle EINTR

[Aidan Gauland <aidalgol@no8wireless.co.nz>]

> Aidan, do you have a test case?

I haven't been able to reproduce this with a minimal example, but I can
consistently reproduce it with my IRC bot
<https://github.com/aidalgol/cunning-bot>.

Replace the last two lines (lines 22 and 23) of run-cbot.scm with...

(define bot (make-bot "Cunning_Bot" "Cunning_Bot" "Cunning Bot" "chat.freenode.net" 6667))
(sigaction SIGINT
  (lambda ()
    (disconnect-bot bot)))
(start-bot bot '("#cunningbot"))

...run it (run-cbot.scm), and after it says

Setting up IRC connection...done.
Joining channels...done.

type ^C

I get this backtrace:

^CBacktrace:
In ice-9/boot-9.scm:
 157: 12 [catch #t #<catch-closure 9a1020> ...]
In unknown file:
   ?: 11 [apply-smob/1 #<catch-closure 9a1020>]
In ice-9/boot-9.scm:
  63: 10 [call-with-prompt prompt0 ...]
In ice-9/eval.scm:
 421: 9 [eval # #]
In ice-9/boot-9.scm:
2131: 8 [save-module-excursion #<procedure 9a01c0 at ice-9/boot-9.scm:3711:3 ()>]
3718: 7 [#<procedure 9a01c0 at ice-9/boot-9.scm:3711:3 ()>]
In unknown file:
   ?: 6 [load-compiled/vm "/home/aidan/.cache/guile/ccache/2.0-LE-8-2.0/home/aidan/src/cunning-bot/run-cbot.scm.go"]
In /home/aidan/src/cunning-bot/bot.scm:
 260: 5 [start-bot # #]
 115: 4 [read-line-irc #]
In ice-9/rdelim.scm:
 129: 3 [read-line #<input-output: socket 11> trim]
In unknown file:
   ?: 2 [%read-line #<input-output: socket 11>]
In ice-9/boot-9.scm:
 184: 1 [throw system-error "fport_fill_input" "~A" ("Interrupted system call") (4)]
In /home/aidan/src/cunning-bot/run-cbot.scm:
  24: 0 [#<procedure 12007a0 at /home/aidan/src/cunning-bot/run-cbot.scm:24:2 ()> 2]

/home/aidan/src/cunning-bot/run-cbot.scm:24:2: In procedure #<procedure 12007a0 at /home/aidan/src/cunning-bot/run-cbot.scm:24:2 ()>:
/home/aidan/src/cunning-bot/run-cbot.scm:24:2: Wrong number of arguments to #<procedure 12007a0 at /home/aidan/src/cunning-bot/run-cbot.scm:24:2 ()>

Could this be caused by a bug in spells?

I wish I could give a simpler test case. :(

Regards,
Aidan Gauland

(Sorry I forgot to group reply the first time.)