#715: Parents probably not reclaimed due to too much caching
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Reporter: robertwb |
Owner: somebody
Type: defect |
Status: needs_review
Priority: major |
Milestone: sage-5.4
Component: coercion |
Resolution:
Keywords: weak cache coercion Cernay2012 | Work
issues:
Report Upstream: N/A |
Reviewers: Jean-Pierre Flori, Simon King, Nils Bruin
Authors: Simon King, Jean-Pierre Flori | Merged
in:
Dependencies: #9138, #11900, #11599, to be merged with #11521 |
Stopgaps:
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Comment (by nbruin):
OK, in principle it is possible to handle segfaults with code like:
{{{
import signal
import os, sys
import traceback
def handler(a,frm):
tb=traceback.extract_stack(frm)
traceback.print_tb(tb,sys.stderr)
sys.stderr.flush()
os._exit(255)
signal.signal(signal.SIGSEGV,handler)
}}}
Of course, with a serious corruption, it's doubtful that code can run
successfully. Indeed, if we equip the doctesting script with it, we don't
get useful information. It makes the script loop forever.
I cannot debug on bsd because OSX wants admin credentials. However, I
think it is possible to attach gdb to running processes, in which case it
might be possible to poke around in the corpse a bit.
See
{{{
bsd.math.washington.edu:/scratch/nbruin/sage-5.4.beta0/segv_handle_infinite_loop.py
}}}
I've also tried to put `gc.collect()` in the doctest. If you put it early
enough in the file (either before or a bit after the `an_element` call),
it prevents the segfault. If you put it right before the test where the
segfault happens, the collection itself does not lead to a segfault, but a
segfault still happens. This is all consistent with a corruption that
happens at one point and triggers a fault somewhere else. Is there a way
to put a command in the doctest that would drop us into a (python)
debugger or a REPL? then we could pick through the memory and see if
there's anything unsavoury.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/715#comment:288>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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