Bugs item #1144263, was opened at 2005-02-19 03:20
Message generated for change (Comment added) made by logistix
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Category: Python Interpreter Core
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Matthew G. Knepley (knepley)
Assigned to: Nobody/Anonymous (nobody)
Summary: reload() is broken for C extension objects
Initial Comment:
1) A C extension module (foo.so) is imported
import foo
2) The library foo.so is rebuilt with changes
3) We reload the module
foo = reload(foo)
The reload() method calls imp.load_dynamic() which
eventually gets down to _PyImport_GetDynLoadFunc().
This just calls dlopen(), which returns the old filehandle.
This problem can be fixed by augmenting imp with
unload_dynamic(), which could easily be implemented in
a _PyImport_GetDynUnloadFunc(), which would just
consult its handles[] array, and call dlclose() on the
appropriate handle. This will work if Python was the
only program to dlopen() foo.so.
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Comment By: logistix (logistix)
Date: 2005-03-08 14:59
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I don't know if this is a viable general-purpose fix. Keep in
mind that python tracks everything by references, and
reloading doesn't correct existing bindings. If you recompile it
is going to screw up existing function pointers in
PyCFunction objects. In the example below calling a() will
probably end up executing random code or generting a
memory fault.
>>> import select
>>> a = select.select
... imaginary recompile ...
>>> reload(select)
<module 'select' from 'C:\Python24\DLLs\select.pyd'>
>>> b = select.select
>>> id(a)
18165472
>>> id(b)
18165476
>>> a() #BOOM!
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Comment By: Matthew G. Knepley (knepley)
Date: 2005-02-19 22:34
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I have coded the proposed solution (changed import.c,
importdl.c, and dynload_shlib.c). I will assemble a test
case for it next week.
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Comment By: Matthew G. Knepley (knepley)
Date: 2005-02-19 15:37
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I am only interested in fixing it for the dlopen() case,
which I thnk subsumes every architecture likely to have this
problem appear. I have no problem fixing it myself, but I
need to get all the CVS stuff setup. And I am not sure how
to easily generate the patch to send (I'm used to BK).
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Comment By: Michael Hudson (mwh)
Date: 2005-02-19 15:27
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I don't believe this is quite as easy as you make out. It might be
possible to make something that works for platforms that use dlopen
though...
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