Memory leak in QByteArray

Hello,

I've encountered a subtle yet persistent memory leak through pyqtgraph application.

In essense, it is caused during construction of QPainterPath using combination of QByteArray and numpy.ndarray's buffer interface. Going to the core, the following code reproduces the bug using just memoryview and QByteArray.

import psutil
from PySide6 import QtCore

proc = psutil.Process()
rss0 = proc.memory_info().rss

for cnt in range(300_010):
    if cnt % 10_000 == 0:
        rss = proc.memory_info().rss
        print(f'{cnt}: {(rss - rss0)/1048576:.1f} MB')

    backstore = QtCore.QByteArray()
    backstore.resize(8192)
    memoryview(backstore)

The problem was successfully reproduced on Linux and MacOc, but possibly not on Windows. Affected version seems to be 6.7.3 where the memleak occured first.

There's a discussion at pyqtgraph about the problem with further details.

https://github.com/pyqtgraph/pyqtgraph/issues/3265#issuecomment-2689480190