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Posted by Ilya Zakharevich on March 29, 2008, 4:49 pm
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[A complimentary Cc of this posting was sent to
Bart Lateur
> Joost Diepenmaat wrote:
>
> >END blocks are useful to "guarantee" that code gets run when the program
> >ends, even if for example an exception is thrown. Useful for system
> >resources that may not get freed properly otherwise.
>
> Unfortunately they're still not called on exit and on exec.
You mean "Fortunately they are not called on _exit(); do not forget to
never use exec()"?
[END() IS called on exit(). Signal handlers can be installed to die()
on signal, so END() is called on signals.]
Hope this helps,
Ilya
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Posted by Ben Morrow on March 29, 2008, 6:30 pm
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> [A complimentary Cc of this posting was sent to
> Bart Lateur
> > Joost Diepenmaat wrote:
> >
> > >END blocks are useful to "guarantee" that code gets run when the program
> > >ends, even if for example an exception is thrown. Useful for system
> > >resources that may not get freed properly otherwise.
> >
> > Unfortunately they're still not called on exit and on exec.
>
> You mean "Fortunately they are not called on _exit();
Well, no, that's kind-of the point...
> do not forget to never use exec()"?
I am confused. How is one (on a fork/exec-based system, or perl's
emulation of such under Win32) supposed to avoid calling exec when
necessary?
> [END() IS called on exit(). Signal handlers can be installed to die()
> on signal, so END() is called on signals.]
END blocks are not called when a process exits because of the DEFAULT
action of a signal. It is of course possible to fix this by installing
an appropriate signal handler.
Ben
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Posted by Joost Diepenmaat on March 29, 2008, 6:45 pm
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> I am confused. How is one (on a fork/exec-based system, or perl's
> emulation of such under Win32) supposed to avoid calling exec when
> necessary?
By using fork(), ofcourse! Am I missing something?
--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/
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Posted by Ben Morrow on March 29, 2008, 8:56 pm
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>
> > I am confused. How is one (on a fork/exec-based system, or perl's
> > emulation of such under Win32) supposed to avoid calling exec when
> > necessary?
>
> By using fork(), ofcourse! Am I missing something?
Err... yes? fork creates a clone of the current process, exec changes
which file the current process is executing. Any method of executing an
external program, on Unix, ends up calling exec.
Ben
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Posted by Joost Diepenmaat on March 29, 2008, 9:39 pm
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>>
>> > I am confused. How is one (on a fork/exec-based system, or perl's
>> > emulation of such under Win32) supposed to avoid calling exec when
>> > necessary?
>>
>> By using fork(), ofcourse! Am I missing something?
>
> Err... yes? fork creates a clone of the current process, exec changes
> which file the current process is executing. Any method of executing an
> external program, on Unix, ends up calling exec.
But for the purposes of END blocks, using fork() before an exec() would
allow the END blocks to run anyway:
# simplified:
END {
# clean up stuff here
# assuming close-on-exec & equivalents are correctly set
}
if (! fork()) { # assumin fork() doesn't fail here.
exec $whatever;
exit;
}
exit;
This is assuming the fork() or exec() themselves won't introduce new
issues.
--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/
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