-Wexpansion-to-defined warnings

[Dan Smith]

I'm suddenly getting hundreds of these warnings when I build in macOS:

/Users/dan/Dev/jdk/jdk/src/hotspot/share/gc/g1/heapRegionSet.hpp:126:5: warning: macro expansion producing 'defined' has undefined behavior [-Wexpansion-to-defined]
#if HEAP_REGION_SET_FORCE_VERIFY
    ^
/Users/dan/Dev/jdk/jdk/src/hotspot/share/gc/g1/heapRegionSet.hpp:53:38: note: expanded from macro 'HEAP_REGION_SET_FORCE_VERIFY'
#define HEAP_REGION_SET_FORCE_VERIFY defined(ASSERT)
                                     ^

Not clear what triggered them, but my guess is an Xcode update.

Is this a known problem? Can anyone reproduce?