[issue32045] Does json.dumps have a memory leak?

[Cheryl Sabella]

Change by Cheryl Sabella :


--
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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[issue32045] Does json.dumps have a memory leak?

[Rohan D'Sa]

Rohan D'Sa  added the comment:

Yes. Thanks.

On 30 Jan 2018 8:31 PM, "Cheryl Sabella"  wrote:

>
> Cheryl Sabella  added the comment:
>
> Can this be closed as 'Not a Bug'?
>
> --
> nosy: +csabella
>
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[issue32045] Does json.dumps have a memory leak?

[Cheryl Sabella]

Cheryl Sabella  added the comment:

Can this be closed as 'Not a Bug'?

--
nosy: +csabella

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[issue32045] Does json.dumps have a memory leak?

[Rohan D'Sa]

Rohan D'Sa  added the comment:

you are right. i realized later i actually had a leak in a com instantiated 
object, assumed it was a leak in the python and tried to find it using the gc 
module. 

The gc documentation led me down the garden path.

QUOTE

gc.garbage
A list of objects which the collector found to be unreachable but could not be 
freed (uncollectable objects). 

UNQUOTE

i assumed:
- cyclic references are unreachable but can be freed and hence collectable.
- __del__ finalizer (with cyclic references?) objects are unreachable and 
cannot be freed and hence uncollectable.

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[issue32045] Does json.dumps have a memory leak?

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

indent=True just makes json to use Python implementation instead of C 
implementation. Python implementation uses closures which reference one other. 
Simple example not involving json is:

import gc

def f():
def g():
return h
def h():
return g
return

gc.set_debug(gc.DEBUG_LEAK)
while True:
f()
gc.collect()
print(f"garbage count: {len(gc.garbage)}")


The "leak" is caused by using gc.set_debug(gc.DEBUG_LEAK). gc.DEBUG_LEAK 
includes gc.DEBUG_COLLECTABLE, gc.DEBUG_UNCOLLECTABLE and gc.DEBUG_SAVEALL. 
gc.DEBUG_SAVEALL causes garbage-collected objects to be saved in gc.garbage for 
inspection. In normal circumstances they are collected.

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nosy: +pitrou, serhiy.storchaka

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[issue32045] Does json.dumps have a memory leak?

[Rohan D'Sa]

New submission from Rohan D'Sa :

import gc, json

class leak(object):
def __init__(self):
pass

gc.set_debug(gc.DEBUG_LEAK)
while True:
leak_ = leak()
json.dumps(leak_.__dict__, indent=True)
gc.collect()
print(f"garbage count: {len(gc.garbage)}")

Using the following code under Python 3.6.3, the garbage count keeps increasing 
and windows task manager records steady memory increase.

However without indent json.dumps(self.__dict__), no leak is observed.

--
components: Library (Lib)
messages: 306344
nosy: rohandsa
priority: normal
severity: normal
status: open
title: Does json.dumps have a memory leak?
versions: Python 3.6

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