slice_count overflow for very large allocations #876Description
This was seen in python/cpython#117755 on s390x (Linux on IBMz) for an allocation of 0x7fffffffffffffff bytes:
Lines 617 to 618 in f199b88
The mi_segment_os_alloc is successful (possibly due to overcommit), but then the slice_count is truncated, which leads to either an assertion error (in debug builds) or floating point error due to a divide by zero.