longjmp() from nested signal handlers

[Daniel R. Levy]

In article <3669 at sdcc6.ucsd.EDU>, ix426 at sdcc6.ucsd.EDU (Tom Stockfisch) writes:
# In article <26739 at amdahl.uts.amdahl.com> nw at amdahl.uts.amdahl.com (Neal Weidenhofer) writes:
# >...  Using longjump from a signal handler ALWAYS results in
# >undefined behavior.
# 
# This *greatly* reduces the value of signals.
# I like to longjmp() back to a main processing loop on SIGINT.  If 
# all I do is set a flag and return,
# then I have to check that flag in a million other places to see if a user
# is trying to get my attention.

On the other hand, this can be desired.  You might be in an iterative procedure
where internal data is in a consistent state only in a few well-defined places.
Even if this isn't so, a careful look at any protracted, iterative sequence
of code that you want to be able to "bust out of" with a signal will reveal
"high traffic" areas where you can put the check; you don't need to put the
check in a "million other places."
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