>>>>>>>>>>>>>>>>>> Original Message <<<<<<<<<<<<<<<<<<
On 28.01.00, 17:24:04, "Kenn Humborg" <kenn at bluetree.ie> wrote regarding
RE: [ILUG] signals and c++:
> For asynchronous signals like SIGINT, it really depends on what
> you are trying to do. What are you trying to achieve by ensuring
> that destructors get called?
> o Are you trying to ensure that resources get deallocated?
> That doesn't matter if the process is going to be killed.
> (See note below on affecting stuff outside the process.)
> If the signal will be handled and ignored, then it doesn't
> matter because the code won't notice it.
> o If you want to use a signal to partially unwind the call
> stack, and use destructors for resource deallocation and
> cleanup, then it's really tricky. This is really the
> only case that requires further thought.
What particularly bugs me are the synchronized signals such as SIGPIPE
and so forth. It would be nice to be able to protect a call on an
dlopened plugin object with a SEGV exception handler, but that might
be pushing the boat out a bit far.
But there are a load of cases where an asynchronous signal that causes
an exit and bypasses destructors that would do some resource release
that would be useful for the system, but which are not examples of
badly designed resource allocation issues. Things that while maybe not
critical to the system, but do leave cruft and general disarray about
the place. e.g. Using shmget and exiting without a deleting shmctl().
Not deleting tmp files, though use of tmpfile() would sort that one
out. X windowing apps that might like to cleanly XUnmapWindow()
themselves from the screen, and not leave big blank canvases which the
Xserver leaves around for a while until it cops that the app is gone
Some sort of solution might be possible for apps with message queues
by making the signal handler empty the queue and insert a quit message
onto it, and then leave it up to the app to come across it in the near
future and act on it. But thats hardly ideal.
It is just a pity that there doesn't appear to be a nice way to hook
signals and c++ together neatly, I think theres a strong case for
being allowed squidge the bastards into exceptions.
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