This is not much of a gain for the CTracer, but for PyTracer.

With this patch tox -e py37-coverage -- testing/test_asser* in pytest's repo takes 50.5s, without it 116.7s (using timid = 1 to use the PyTracer).

CTracer: 20.5s without this patch, 20.0s with it (but just run once, it is likely due to a function call being less of an overhead in C).