Some documents explain passing MIMALLOC_STATS=1 to print
statistics, though it handles as mimalloc_show_stats in the actual
code. According to the code, change the name MIMALLOC_STATS to MIMALLOC_SHOW_STATS.
In 2012, with the release of OS X 10.8 Mountain Lion, the name of the
system was shortened from Mac OS X to OS X. In 2016, with the release
of macOS 10.12 Sierra, the name was changed from OS X to macOS to
streamline it with the branding of Apple's other primary operating
systems: iOS, watchOS, and tvOS.
Reference: https://en.wikipedia.org/wiki/MacOS
David Carlier