import matplotlib.pyplot as plt

fig=plt.figure(1)
ax1=fig.add_subplot(1,2,1)
ax1.loglog(range(10))
ax2=fig.add_subplot(1,2,2, sharex=ax1)
ax2.loglog(range(10))

fig.clf()

Throws a warning:
UserWarning: Attempted to set non-positive xlimits for log-scale axis; invalid limits will be ignored.
'Attempted to set non-positive xlimits for log-scale axis;

ax1.cla() also throws a warning.

Matplotlib version
2.1.0,
python 3.6.3
ipython 6.1.0