Another message that surprises me is:
Warning -- multiprocessing.process._dangling was modified by test_multiprocessing_spawn
  Before: <_weakrefset.WeakSet object at 0x3076e810>
  After:  <_weakrefset.WeakSet object at 0x3076e390>

Normally speaking the address 0x30000000 and higher should be "out of bounds" aka a SEGV - unless special actions are taken to open a memory region above 0x2fffffff - for default AIX memory model.

Just calling malloc(), afaik, does not do automatically create a new memory section (0x0000000-0x0fffffff is reserved for kernel CODE, 0x10000000-0x1fffffff is reserved for application CODE, and 0x20000000-0x2fffffff is .data,.bss, "empty aka not-active", .stack).
The area between .end_bss and .stack is the area that sbrk() provides memory from (for calls to malloc(), e.g.)

In short, is there something I do not know understand about Python object pointers that 0x30000000+ values are actually living in 0x20000000-0x2fffffff space?