Re: [MacPerl] Alarm Signal in MacPerl

[Matthias Ulrich Neeracher <neeri@iis.ee.ethz.ch>]

Chris Nandor <pudge@pobox.com> writes:
>At 12.55 -0500 1998.06.04, John Gilmore-Baldwin wrote:
>>#!perl -wl
>>use CGI qw(:all);
>>$SIG{ALRM} = \&do_die;
>>print header('text/plain');
>>alarm(5);
>>foreach(0..99){print;sleep(1)}
>>sub do_die {print "Time's up!";exit}
>>
>>This returns to me after 5 seconds, instead of 100:
>
>Of course it returns after 5 seconds.  You set alarm(5).  I am not sure I
>understand.  Maybe you expected it to return after 5 seconds; I do.

Presumably, John wanted to demonstrate the difference between a program where
alarm works as expected and his connect example where it didn't work.

>As to the signal being unreliable, that is a function of virtually all
>signals in Perl, I think.  When Perl is out doing socket operations, it is
>possible (I think) for a SIGALRM to not report as it should, just as cmd-.
>does not always work during such operations.

 - In "perl" as such, alarm() should work.
 - If it doesn't work with some functions in MacPerl, it's either because of a
   bug or because in that call, I saw no safe opportunity to cancel the call.
 - At the moment, I don't know which of these cases applies to connect(), nor
   do I really care, because the GUSI 2 rewrite should take care of that.

Matthias

-- 
Matthias Neeracher   <neeri@iis.ee.ethz.ch>   http://www.iis.ee.ethz.ch/~neeri
   "I'm set free to find a new illusion" -- Velvet Underground

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