[Python-Dev] Testing Socket Timeouts patch 1519025

[Tony Nelson]

At 2:38 PM -0700 7/29/06, Josiah Carlson wrote:
>Tony Nelson <tonynelson at georgeanelson.com> wrote:
>>
>> I'm trying to write a test for my Socket Timeouts patch [1], which fixes
>> signal handling (notably Ctl-C == SIGINT == KeyboarInterrupt) on socket
>> operations using a timeout.  I don't see a portable way to send a signal,
>> and asking the test runner to press Ctl-C is a non-starter.  A "real"
>> signal is needed to interrupt the select() (or equivalent) call, because
>> that's what wasn't being handled correctly.  The bug should happen on the
>> other platforms I don't know how to test on.
>>
>> Is there a portable way to send a signal?  SIGINT would be best, but
>> another signal (such as SIGALRM) would do, I think.
>
>According to my (limited) research on signals, Windows signal support is
>horrible.  I have not been able to have Python send signals of any kind
>other than SIGABRT, and then only to the currently running process,
>which kills it (regardless of whether you have a signal handler or not).

Hmm, OK, darn, thanks.  MSWindows does allow users to press Ctl-C to send a
KeyboardInterrupt, so it's just too bad if I can't find a way to test it
from a script.


>> If not, should I write the test to only work on systems implementing
>> SIGALRM, the signal I'm using now, or implementing kill(), or what?
>
>I think that most non-Windows platforms should have non-braindead signal
>support, though the signal module seems to be severely lacking in
>sending any signal except for SIGALRM, and the os module has its fingers
>on SIGABRT.

The test now checks "hasattr(signal, 'alarm')" before proceeding, so at
least it won't die horribly.


>If someone is looking for a project for 2.6 that digs into all sorts of
>platform-specific nastiness, they could add actual signal sending to the
>signal module (at least for unix systems).

Isn't signal sending the province of kill (2) (or os.kill()) in python)?
Not that I know much about it.

BTW, I picked SIGALRM because I could do it all with one thread.  Reading
POSIX, ISTM that if I sent the signal from another thread, it would bounce
off that thread to the main thread during the call to kill(), at which
point I got the willies.  OTOH, if kill() is more widely available than
alarm(), I'll give it a try, but going by the docs, I'd say it isn't.
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