This issue tracker has been migrated to GitHub, and is currently read-only.
For more information, see the GitHub FAQs in the Python's Developer Guide.

Author frispete
Recipients frispete
Date 2016-12-14.11:36:47
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <1481715408.44.0.569114702165.issue28970@psf.upfronthosting.co.za>
In-reply-to
Content
In an attempt of using ctypes.from_buffer() to map a structure to a memory mapped file, it is important to destroy the mapping after use, because the mmap won't be resizable or freeable correctly until then.

The best approach, I was able to came up with is using a context manager, but calling the dtor of the mapping in __exit__ is not enough, which results to code like this:

with StructMap(ctypes_struct, mm, offest) as smap:
    smap.xxx = 'blabla'
del smap # necessary, but ugly

Without the del, the "with" variable still exist in the local context, hence the mapping still exist, until it is explicitly destroyed.

I hope, that ctypes is able to (or can be made to) actively remove the mapping in the __exit__ part of the context manager.

I've put some code on stackoverflow to play with this:

http://stackoverflow.com/questions/41077696/python-ctypes-from-buffer-mapping-with-context-manager-into-memory-mapped-file

The problem seems to exist with the linux mmap implementation only.
History
Date User Action Args
2016-12-14 11:36:48frispetesetrecipients: + frispete
2016-12-14 11:36:48frispetesetmessageid: <1481715408.44.0.569114702165.issue28970@psf.upfronthosting.co.za>
2016-12-14 11:36:48frispetelinkissue28970 messages
2016-12-14 11:36:47frispetecreate