While debugging a very strange problem (a simple shell loop that was
occasionally continuing around before the body was done, leading to
multiple parallel runs of something that was supposed to be
serialized) I came across Debian Bug #445956 - "script dies on SIGWINCH."
The bug report simply notes that script "dies", reporting "Script
done, file is typescript", which is true... but incomplete. It turns
out that script has a parent and child process, and only the
parent dies; the child (and whatever was being run inside
script) continues to run!
In the long run, the important thing is that bsd-utils actually
got fixed (the bug mentioned above is closed by 2.13-9, though that
is post-etch and post-gutsy.) In the short run, it would
be nice (at least for me) to have a workaround...
My first attempt was simply to use signal.signal to set
SIGWINCH to SIG_IGN (in the python wrapper that actually
runs script for me.) Not good enough - the bug is in code that
is setting a SIGWINCH handler in script itself.
Second attempt was to call sigblock... but for portability
reasons (somewhat tied to embedding python in other code, if I
correctly interpreted the postings excusing its absence - I didn't
look to closely because having a good reason didn't actually solve my
problem :-) python's signal module can't do sigblock. Oh
well, ctypes to the rescue; fixed_script.py shows an
example of the workaround. Worked for me, both in my application and
in standalone tests using screen to change window sizes (I use
ratpoison and generally don't want windows to take up less than
the entire screen, so outside of testing like this I don't generally
care that I can't easily resize windows... I only noticed in this case
because I reattached the screen session from two different machines,
which had different (fixed) window sizes :-)
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