| msg136485 - (view) |
Author: (poq) |
Date: 2011-05-21 22:39 |
| When importing ctypes after gc.set_debug(gc.DEBUG_LEAK), the garbage collector finds a 'c_int_Array_3' class and some related objects. The class is created in ctypes/_endian.py: _array_type = type(c_int * 3) It seems that this could be avoided with: _array_type = type(Array) Of course, I realize this is not a bug because normally it will just get collected. It is just an extremely minor annoyance because this is currently the only thing still found by DEBUG_LEAK for my program ;) |
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| msg137148 - (view) |
Author: Terry J. Reedy (terry.reedy) *  |
Date: 2011-05-28 19:50 |
| If you are able to rebuild Python, have you tried running the ctypes test after rebuilding with this change? And, does the test cover the internal uses of _array_type? |
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| msg137371 - (view) |
Author: (poq) |
Date: 2011-05-31 17:07 |
| Tests succeed with this change. There is only one use of _array_type, which is in the same module. This use is presumably tested, because the test fails if I change the line to _array_type = type(Structure). In fact, everything must behave exactly the same after this change, because the two values are identical: >>> from ctypes import * >>> type(c_int * 3) is type(Array) True |
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| msg137379 - (view) |
Author: Terry J. Reedy (terry.reedy) * |
Date: 2011-05-31 18:25 |
| Thank you for the test and explanation. There currently is no specific cytpes maintainer. But from what you have said, I might feel comfortable enough applying this, if no one else does, when I have the necessary setup on a new machine. |
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| msg140098 - (view) |
Author: Vlad Riscutia (vladris) |
Date: 2011-07-11 04:16 |
| I ran full test suit after making the _array_type = type(Array) change and everything passes. I also took a look at this and found additional leak. gc shows this as garbage: [(<class '_ctypes._SimpleCData'>,), <class 'ctypes.c_longdouble'>, <attribute '_ _dict__' of 'c_longdouble' objects>, <attribute '__weakref__' of 'c_longdouble' objects>, (<class 'ctypes.c_longdouble'>, <class '_ctypes._SimpleCData'>, <class '_ctypes._CData'>, <class 'object'>), {'__dict__': <attribute '__dict__' of 'c_ longdouble' objects>, '_type_': 'g', '__module__': 'ctypes', '__weakref__': <att ribute '__weakref__' of 'c_longdouble' objects>, '__doc__': None}] This is all caused by these lines in ctypes __init__.py: class c_longdouble(_SimpleCData): _type_ = "g" if sizeof(c_longdouble) == sizeof(c_double): c_longdouble = c_double For me sizeof(c_longdouble) == sizeof(c_double) (I believe MS compiler always does this) but when we assign c_longdouble = c_double, there is a leak. I removed the alias lines: if sizeof(c_longdouble) == sizeof(c_double): c_longdouble = c_double And the leak was gone. Looks like changing c_longdouble after declaring it causes a leak. Below for similar aliasing of longlong types, we have this: if _calcsize("l") == _calcsize("q"): # if long and long long have the same size, make c_longlong an alias for c_long c_longlong = c_long c_ulonglong = c_ulong else: class c_longlong(_SimpleCData): _type_ = "q" _check_size(c_longlong) class c_ulonglong(_SimpleCData): _type_ = "Q" This avoids declaring c_longlong and c_ulonglong as class if not needed to. The problem is _calcsize("g") causes an error because "g" is used as long double througout ctypes but _calcsize is function from _struct.c, where "g" (long double) is not defined. Not sure why it isn't... So in short: As far as I can tell _array_type = type(Array) doesn't break anything Looks like we have another leak in ctypes (which isn't a big deal) We have elegant fix for the leak once _struct.c will support long double |
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| msg152552 - (view) |
Author: (poq) |
Date: 2012-02-03 20:10 |
| I've attached a patch for the _array_type change. The long double fix is probably dependent on PEP3118 (#3132). |
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| msg152661 - (view) |
Author: Roundup Robot (python-dev)  |
Date: 2012-02-05 06:29 |
| New changeset 205da7a19a78 by Meador Inge in branch '3.2': Issue #12142: Fixed reference cycle when importing ctypes http://hg.python.org/cpython/rev/205da7a19a78 New changeset b228d9da8bd3 by Meador Inge in branch 'default': Issue #12142: Fixed reference cycle when importing ctypes http://hg.python.org/cpython/rev/b228d9da8bd3 New changeset 7cdbf627f958 by Meador Inge in branch '2.7': Issue #12142: Fixed reference cycle when importing ctypes http://hg.python.org/cpython/rev/7cdbf627f958 |
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| msg164258 - (view) |
Author: Amaury Forgeot d'Arc (amaury.forgeotdarc) * |
Date: 2012-06-28 14:28 |
| Meador, can we close this issue? |
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| msg164262 - (view) |
Author: Meador Inge (meador.inge) * |
Date: 2012-06-28 14:53 |
| > Meador, can we close this issue? I wanted to keep it open until the 'long double' problem is fixed as well. |
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| msg408111 - (view) |
Author: Irit Katriel (iritkatriel) * |
Date: 2021-12-09 12:17 |
| Looks like the long double issue is still there in 3.11 >>> import gc >>> gc.set_debug(gc.DEBUG_LEAK) >>> import ctypes gc: collectable <function 0x0000026417BBE200> gc: collectable <tuple 0x0000026417BE0040> gc: collectable <dict 0x0000026417BC56C0> gc: collectable <type 0x0000026417AD9840> gc: collectable <tuple 0x0000026417BD6540> gc: collectable <getset_descriptor 0x0000026417BD6580> gc: collectable <getset_descriptor 0x0000026417BD65C0> gc: collectable <tuple 0x0000026417BE05E0> gc: collectable <_ctypes.PyCSimpleType 0x0000026417AE4E10> gc: collectable <tuple 0x0000026417BD96C0> gc: collectable <getset_descriptor 0x0000026417BE9080> gc: collectable <getset_descriptor 0x0000026417BE90C0> gc: collectable <StgDict 0x00000264178A5490> >>> gc.garbage [<function _C._m at 0x0000026417BBE200>, (<class 'object'>,), {'__module__': 'types', '_m': <function _C._m at 0x0000026417BBE200>, '__dict__': <attribute '__dict__' of '_C' objects>, '__weakref__': <attribute '__weakref__' of '_C' objects>, '__doc__': None}, <class 'types._C'>, (<class 'types._C'>, <class 'object'>), <attribute '__dict__' of '_C' objects>, <attribute '__weakref__' of '_C' objects>, (<class '_ctypes._SimpleCData'>,), <class 'ctypes.c_longdouble'>, (<class 'ctypes.c_longdouble'>, <class '_ctypes._SimpleCData'>, <class '_ctypes._CData'>, <class 'object'>), <attribute '__dict__' of 'c_longdouble' objects>, <attribute '__weakref__' of 'c_longdouble' objects>, {'__module__': 'ctypes', '_type_': 'g', '__dict__': <attribute '__dict__' of 'c_longdouble' objects>, '__weakref__': <attribute '__weakref__' of 'c_longdouble' objects>, '__doc__': None}] |
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| msg408121 - (view) |
Author: Eryk Sun (eryksun) * |
Date: 2021-12-09 13:37 |
| The _ctypes extension module could have a dict that maps each format code to its (size, alignment), based on `formattable`. Then direct size comparisons wouldn't be limited to types defined by the struct module, and it wouldn't be necessary to create c_longdouble just to check its size and throw it away. |
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