#14471: Category refinement sometimes changes the hash of parents
--------------------------------+-------------------------------------------
       Reporter:  vbraun        |         Owner:  rlm         
           Type:  defect        |        Status:  needs_review
       Priority:  major         |     Milestone:  sage-5.10   
      Component:  memleak       |    Resolution:              
       Keywords:                |   Work issues:              
Report Upstream:  N/A           |     Reviewers:              
        Authors:  Volker Braun  |     Merged in:              
   Dependencies:                |      Stopgaps:              
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Description changed by vbraun:

Old description:

> Under some circumstances the !WeakValueDictionary remove callback is
> being called when the internal dictionary is in a bad state. The attached
> patch [attachment:trac_14471_demonstrate.patch] to demonstrate the issue
> just calls `hasattr` from the displayhook, which ends up generating weak
> references somewhere. The exact place for where the exception occurs
> depends on the garbage collector, but I always do get some unwanted
> exceptions with it.
> {{{
> sage -t devel/sage/sage/matrix/matrix0.pyx
> Exception KeyError: (((<class 'sage.matrix.matrix_space.MatrixSpace'>,
> Callable function ring with arguments (x, y), 2, 2, False), ()),) in
> <function remove at 0x18d8758> ignored
> **********************************************************************
> File "devel/sage/sage/matrix/matrix0.pyx", line 3370, in
> sage.matrix.matrix0.Matrix.is_hermitian
> Failed example:
>     B.is_hermitian()
> Expected:
>     True
> Got:
>     Exception KeyError: (((<class 'sage.categories.algebras.Algebras'>,
> Callable function ring with arguments (x, y)), ()),) in <function remove
> at 0x18d8758> ignored
>     True
> }}}
>
> Apply [attachment:trac_14471_dynamic_class_hash.patch]

New description:

 Old title: Exception KeyError: in WeakValueDictionary remove ignored

 Under some circumstances the !WeakValueDictionary remove callback is being
 called when the internal dictionary is in a bad state. The attached patch
 [attachment:trac_14471_demonstrate.patch] to demonstrate the issue just
 calls `hasattr` from the displayhook, which ends up generating weak
 references somewhere. The exact place for where the exception occurs
 depends on the garbage collector, but I always do get some unwanted
 exceptions with it.
 {{{
 sage -t devel/sage/sage/matrix/matrix0.pyx
 Exception KeyError: (((<class 'sage.matrix.matrix_space.MatrixSpace'>,
 Callable function ring with arguments (x, y), 2, 2, False), ()),) in
 <function remove at 0x18d8758> ignored
 **********************************************************************
 File "devel/sage/sage/matrix/matrix0.pyx", line 3370, in
 sage.matrix.matrix0.Matrix.is_hermitian
 Failed example:
     B.is_hermitian()
 Expected:
     True
 Got:
     Exception KeyError: (((<class 'sage.categories.algebras.Algebras'>,
 Callable function ring with arguments (x, y)), ()),) in <function remove
 at 0x18d8758> ignored
     True
 }}}

 Apply [attachment:trac_14471_dynamic_class_hash.patch]

--

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14471#comment:25>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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