Memory leaks

Use valgrind or something similar to find memory leaks in the executable. This is not a huge priority, since most people just run this as a one-off executable, but if a longer-running application were using this as a library, they could have issues.

Start by running the executable under Valgrind or a similar memory-checking tool and record any reported leaks. Trace each report to the relevant C++ code, then verify with the same tool that the executable no longer reports leaks when the investigation is complete.

Written by the indexing model from the issue text.