I'm currently testing the 1.4.0rc1 (had to change the min_version of freetype2 to 1.3, see #3262). It seems that the memory leak reported in #3197 is gone, but I still see a very slow but considerable increase in resident memory, and in fact I can observe a constant Python object count growth of the following classes:

__builtin__.list 14645  +114
__builtin__.dict    18076   +114
matplotlib.font_manager.FontProperties  761 +114

(measured using objgraph)

So I think between 1.3.1 and 1.4.0rc1 some kind of new "leak" appeared on Python level. It's not a real leak as the objects are accessible, so I guess it's a kind of internal font (property) cache which doesn't clear up old entries.

Test script:

import numpy as np
import matplotlib as mpl
mpl.use('agg')
import matplotlib.pyplot as plt

for i in range(100000):
    fig, ax = plt.subplots()         

    circle1=plt.Circle((0,0),2,color='r',rasterized=True)
    ax.add_artist(circle1)

    fig.savefig('test.svg')
    plt.close(fig)

EDIT: I had measured object count growth for 1.3.1 also, and there was no growth of any class there.