Bug report

Bug summary

Hi,

I believe I have found a memory issue when plotting multiple figures with the macOS backend.

Here is a minimal working example:

import sys
import matplotlib.pyplot as plt
import numpy as np

import matplotlib
#matplotlib.use('agg')

data = np.random.rand(60, 60)

def plot_expr(plot_name):

    plt.figure(figsize=(9, 8))

    for i in range(60):
        plt.plot(data[i, :])

    plt.savefig(plot_name)

    plt.close('all')


if __name__ == "__main__":

    print(f'python: {sys.version}')
    print(f'matplotlib: {matplotlib.__version__}')
    print(f'backend: {matplotlib.get_backend()}')

    for i in range(50):
        print(f'{i}...')
        plot_expr(f'leak_{i}')

When running the code with memory-profiler, I obtain something like:

Even though I am explicitly calling the plt.close() function.

When using the 'agg' backend instead of the 'MacOSX' backend by uncommenting line 6, I get:

Which I would expect to be the normal behavior.

As I have been unable to reproduce this on Linux, I assume that the issue is with the macOS backend.

Matplotlib version

• Operating system: macOS 11.2.1
• Matplotlib version 3.3.4
• Matplotlib backend MacOSX
• Python version: 3.7.9

I installed Python via venv and matplotlib via pip.

Cheers,

Théotime