Spent two days hunting down a memory leak that only impacted and showed up on macOS. Turns out that the the following line caused memory to grow with each garbage collection cycle. The upside is that I became familiar Instruments a great memory and performance monitoring tool that’s included with Xcode. This tool also found a tiny bounded leak in the JIT compilers that leaked extra 4-8 bytes with each compiled function. Luckily, the number of compiled functions is bounded however no other leak tool (i.e. Valgrind Visual Leaks) found it.