#12215: Memleak in UniqueRepresentation, @cached_method
-----------------------------+----------------------------------------------
Reporter: vbraun | Owner: rlm
Type: defect | Status: needs_work
Priority: major | Milestone: sage-5.0
Component: memleak | Keywords: UniqueRepresentation
cached_method caching
Work_issues: Fix two tests | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: #11115 #11900
-----------------------------+----------------------------------------------
Comment(by SimonKing):
Here is some more info on the segfault.
Setting: I have sage-5.0.prealpha0 plus #11780, #11290, #715, #11521,
#12313 and the patches from here, removing the `__dealloc__` method
introduced by the last patch.
The segfault is triggered by doing
{{{
sage: half_integral_weight_modform_basis(DirichletGroup(16,QQ).1, 3, 10)
[]
sage: half_integral_weight_modform_basis(DirichletGroup(16,QQ).1, 5, 10)
/home/simon/SAGE/sage-5.0.prealpha0/local/lib/libcsage.so(print_backtrace+0x31)[0x7fe047add9c6]
/home/simon/SAGE/sage-5.0.prealpha0/local/lib/libcsage.so(sigdie+0x14)[0x7fe047add9f8]
/home/simon/SAGE/sage-5.0.prealpha0/local/lib/libcsage.so(sage_signal_handler+0x20c)[0x7fe047add646]
/lib64/libpthread.so.0(+0xfd00)[0x7fe04cd80d00]
...
}}}
When I revert the lines, that's to say, if I do
{{{
sage: half_integral_weight_modform_basis(DirichletGroup(16,QQ).1, 5, 10)
[q - 2*q^3 - 2*q^5 + 4*q^7 - q^9 + O(q^10)]
sage: half_integral_weight_modform_basis(DirichletGroup(16,QQ).1, 3, 10)
[]
sage: quit
Exiting Sage (CPU time 0m2.02s, Wall time 0m20.49s).
**********************************************************************
Oops, Sage crashed. We do our best to make it stable, but...
A crash report was automatically generated with the following information:
- A verbatim copy of the crash traceback.
- A copy of your input history during this session.
- Data on your current Sage configuration.
It was left in the file named:
'/home/simon/.sage/ipython/Sage_crash_report.txt'
If you can email this file to the developers, the information in it will
help
them in understanding and correcting the problem.
You can mail it to: sage-support at [email protected]
with the subject 'Sage Crash Report'.
If you want to do it now, the following command will work (under Unix):
mail -s 'Sage Crash Report' [email protected] <
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To ensure accurate tracking of this issue, please file a report about it
at:
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Press enter to exit:
}}}
I was tracing all python commands for the first variant of the segfault.
The last few lines of the log are as follows:
{{{
sage.categories.pushout:__call__:2125 if self.p == other.p:
sage.categories.pushout:__call__:2126 from sage.all import
Infinity
sage.categories.pushout:__call__:2127 if self.prec ==
other.prec:
sage.categories.pushout:__call__:2128 extras =
self.extras.copy()
sage.categories.pushout:__call__:3102 except CoercionException:
sage.categories.pushout:__call__:3104 except (TypeError, ValueError,
AttributeError, NotImplementedError), ex:
sage.categories.pushout:__call__:3108 raise CoercionException(ex)
weakref:__call__:49 self = selfref()
weakref:__call__:50 if self is not None:
weakref:__call__:51 del self.data[wr.key]
sage.rings.power_series_ring:__call__:556 s = "Power Series Ring
in %s over %s"%(self.variable_name(), self.base_ring())
sage.rings.power_series_ring:__call__:557 if self.is_sparse():
sage.rings.power_series_ring:__call__:562 return self.__is_sparse
sage.rings.power_series_ring:__call__:559 return s
}}}
So, indeed it seems that the problem has something to do with weak
references. There is an item of a weak value dictionary deleted right
before segfaulting.
To do: Find out what item of what dictionary is deleted, why it is
deleted, and how deletion can be prevented.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12215#comment:68>
Sage <http://www.sagemath.org>
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