Fix memory leaks from "Maybe_Unicode" (fixes #27 #125)

[henryykt]

Attempt to fix memory leaks described in #27 and #125.

[thedrow]

Did you verify this patch with valgrind?

[henryykt]

Did you verify this patch with valgrind?

Tested with the following:

import json

from librabbitmq import Connection, Message

max_iters = 10000

with Connection(
    host="localhost", port=5672, userid="guest", password="guest", virtual_host="/"
) as conn:
    with conn.channel() as channel:
        channel.exchange_declare(exchange="re", type="direct", auto_delete=False)

        data = json.dumps({"some_key": "some_value"})
        props = {"headers": {"some_header": "some_header_value"}}

        while max_iters > 0:
            max_iters -= 1

            message = Message(channel=channel, properties=props, body=data)
            channel.basic_publish(message, 're', routing_key='')

Output master branch:

(venv_librabbitmq) [developer@dev librabbitmq]$ PYTHONMALLOC=malloc valgrind --tool=memcheck --leak-check=full --show-leak-kinds=all python ./publish.py
==26039== Memcheck, a memory error detector
==26039== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==26039== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
==26039== Command: python ./publish.py
==26039==
...
==26039== LEAK SUMMARY:
==26039==    definitely lost: 1,289,804 bytes in 29,996 blocks
==26039==    indirectly lost: 0 bytes in 0 blocks
==26039==      possibly lost: 641,114 bytes in 3,902 blocks
==26039==    still reachable: 1,428,011 bytes in 14,090 blocks
==26039==                       of which reachable via heuristic:
==26039==                         newarray           : 60 bytes in 1 blocks
==26039==         suppressed: 0 bytes in 0 blocks
==26039==
==26039== For counts of detected and suppressed errors, rerun with: -v
==26039== ERROR SUMMARY: 717 errors from 717 contexts (suppressed: 0 from 0)

Output with fix:

(venv_librabbitmq) [developer@dev librabbitmq]$ PYTHONMALLOC=malloc valgrind --tool=memcheck --leak-check=full --show-leak-kinds=all python ./publish.py
==26385== Memcheck, a memory error detector
==26385== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==26385== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
==26385== Command: python ./publish.py
==26385==
...
==26385== LEAK SUMMARY:
==26385==    definitely lost: 0 bytes in 0 blocks
==26385==    indirectly lost: 0 bytes in 0 blocks
==26385==      possibly lost: 640,888 bytes in 3,897 blocks
==26385==    still reachable: 1,427,967 bytes in 14,089 blocks
==26385==                       of which reachable via heuristic:
==26385==                         newarray           : 60 bytes in 1 blocks
==26385==         suppressed: 0 bytes in 0 blocks
==26385==
==26385== For counts of detected and suppressed errors, rerun with: -v
==26385== ERROR SUMMARY: 710 errors from 710 contexts (suppressed: 0 from 0)

[thedrow]

LGTM

[auvipy]

can you rebase?

[henryykt]

can you rebase?

done