#12985: Possible future issues with ECL build with unicode enabled
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Reporter: pcpa |
Owner: was
Type: enhancement |
Status: new
Priority: minor |
Milestone: sage-5.1
Component: interfaces |
Resolution:
Keywords: | Work
issues:
Report Upstream: Reported upstream. Developers deny it's a bug. |
Reviewers:
Authors: | Merged
in:
Dependencies: |
Stopgaps:
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Comment (by nbruin):
Juan's of course right in being concerned that objects are protected
against garbage collection while alive. As far as I know, Boehm does watch
the C stack for pointers, so a local variable pointing to the string
should protect it against garbage collection while in scope.
I'm pretty sure that every `ecl_base_string_pointer_safe` occurs in a
context where a python string object is required. Cython injects a
`PyBytes_FromString` for that, which copies the content into a Python
allocated object. The ECL-managed object is thus extremely short lived and
during its life, is referenced by a local C variable (i.e., is referenced
on the C stack). Boehm is supposed to watch the C stack for references, so
it is protected against GC during its life.
If the reference returned by `ecl_base_string_pointer_safe` were to be
stored in, say, a malloc'd location (or Python managed memory) such
protection is no longer guaranteed. This is why `EclObject.set_obj` makes
the little `remove_node`/`insert_node_after` dance, which ensures that a
reference to the underlying ecl-object is stored within memory watched by
Boehm-GC.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12985#comment:4>
Sage <http://www.sagemath.org>
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