Quite the opposite; jemalloc has been the default, and using the system allocator has been the &quot;hassle&quot; since well before 1.0.<p>However a few key platforms have jemalloc disabled because it&#x27;s buggy (deadlocks or worse). I think as of a few days ago it&#x27;s pretty much universally off on windows.<p>Also whether jemalloc is used depends on how you build your thing -- dylibs use the system allocator (because they&#x27;re subordinate), static libs (rlibs) inherit from the thing they&#x27;re linked into, and executables use jemalloc (because they&#x27;re in control).