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Re: Sending signals to a subprocess

On Sat, Oct 23, 2010 at 10:51:38PM -0400, Ken Brown wrote:
>On 10/20/2010 4:32 PM, Christopher Faylor wrote:
>> On Wed, Oct 20, 2010 at 08:25:37PM +0100, Andy Koppe wrote:
>>> On 20 October 2010 13:20, Andy Koppe wrote:
>>>>> Corinna made tcgetpgrp return 0 instead of -1 in some circumstances
>>>>> (see
>>>>> because she saw Linux doing that.  ??But when I run Corinna's test on
>>>>> my Linux system, I get -1 where she got 0.  ??So not all Linuxes agree
>>>>> on what tcgetpgrp should do.
>>>> Hmm, Corinna's test calls tcgetpgrp(master) in the parent only before
>>>> the child is forked and after it exited, so it's correct to report that
>>>> there's no foreground process.
>>>> I wonder which Linux it was that returned 0 in case of failure.  I've
>>>> tried it on a recent Opensuse, an old Redhat with a 2.6.9 kernel, and
>>>> also a Debian with a 2.4 kernel, and got -1 on all of those.
>>> Actually I'd only tried my test on all three systems, whereas I'd tried
>>> Corinna's only on the old Redhat, where it did print -1 for failure.
>>> On the 2.4 system it can't open /dev/ptmx, whereas on the Opensuse with
>>> 2.6.34 I do get the results Corinna reported, including 0 on the master
>>> side of the pty when enquiring from the parent.  (Process 0 is the
>>> startup process, so I guess that makes some sense.)
>>> To bring my ramblings to some sort of conclusion, here's a slightly
>>> amended version of Corinna's test that checks the master side from the
>>> parent process before, *during* and after the child process:
>> FYI, I'm sticking with the test case that I first posted several days
>> ago and which has been cruelly ignored ever since.  I've been slowly
>> modifying it for the last several days.
>> I think I'm seeing some pattern to the way Linux handles this and I should
>> be able to make Cygwin work the same way.
>This seems to be fixed in the latest snapshot, as far as emacs is 
>concerned.  I no longer see any difference between Cygwin and Linux 
>there.  I also get the expected results when I run the test cases that 
>Andy posted.  But when I run the original test case that you posted in
>I'm getting strange behavior.  I ran it with no argument, getting
>0 = tcgetpgrp(4)
>0 = ioctl(fd, TIOCGPGRP, &pid), pid = 0
>but then the terminal seemed to hang, and I didn't get a new prompt.  I 
>tried this both in mintty and xterm.

I think this falls nicely into the cruelly ignored comment above since I
can get my test case to hang on a Windows 7 system prior to the
inclusion of any of my recent patches.

I'll fix it though.


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