eventually Perl left eval state, with the die handler still set.

Isn't that a rather serious bug in perl (famous last words)? Looking at the code there is no place where a handler capable of dying is possibly called outside eval.

Could a signal get caught while perl was inside the eval block, a Perl-level handler stored somewhere and its execution resumed after the current opcode "exit eval block" finished? But at the ending brace of the eval block the handler should have already been reset. So (blissfully ignorant of perlguts) I'd guess that signals may be delivered to Perl more than one opcode after delivery to perl (yay, I used them both in a single sentence). If the two opcodes interact with the signal delivery process, Bad Things (tm) happen.

Newsflash! Adding a sleep $anything_above_1us (and use Time::HiRes qw( sleep ) of course) between resetting the handlers and the closing brace makes the test pass quite repeatably, at least for me. Sleeping for 1e-6 seconds does not do anything, sleeping for 1.00001e-6 passes the test. Probably has something to do with populating a struct timeval with 1us resolution somewhere.

The difference between two calls clearly shows that Time::HiRes::sleep rounds its argument to microsecond precision and any non-zero value prevents the bug from appearing.

$ strace -e nanosleep perl -MTime::HiRes=sleep -le 'sleep 1.e-6'
nanosleep({0, 0}, NULL)                 = 0
Process 12719 detached
$ strace -e nanosleep perl -MTime::HiRes=sleep -le 'sleep 1.01e-6'
nanosleep({0, 1000}, NULL)              = 0
Process 12721 detached

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In reply to [WORKAROUND] Re^4: Setting signal handlers considered unsafe? by gnosek
in thread Setting signal handlers considered unsafe? by gnosek

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