On 27 July 2017 at 23:48, jan matejek
This is most often found in __init__.py. Often this affects optimized pycs, but we can see it in un-optimized as well. The issue is rare -- 99% of all pycs are stable -- but when it occurs, it's easy to replicate it in the same place. This also happens on different machines, so that seems to rule out hardware memory errors :)
The marshal implementation received some significant optimisations in 3.5 [1] and a new marshal format in 3.4 [2], so if you're able to check the behaviour in 3.4 and 3.5 that would be helpful: if the problem occurs in 3.5, but *not* in 3.4, the hashtable based optimisations would be the place to start looking, while if 3.4 misbehaves as well, then there may be some general inconsistency to resolve in how the module decides which instances to mark with `FLAG_REF`. The fact that disorderfs makes a difference does make me a little suspicious, as there's an early exit from the FLAG_REF setting code related to objects having exactly one live reference. Courtesy of string interning and other immutable object caches, order of code compilation can affect how many live references there are to strings and other constants, and hence there may be cases where marshal *won't* flag an immutable object if *only* that particular code object has been compiled, but *will* flag it if some other code object has been created first. That check has been there since version 3 of the marshal format was defined, so if it *is* the culprit, then you'll see this misbehaviour with 3.4 as well. Cheers, Nick. [1] https://docs.python.org/3/whatsnew/3.5.html#optimizations [2] https://github.com/python/cpython/commit/d7009c69136a3809282804f460902ab42e9... -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia