We could allocate chunks larger than 4GB, but did our
size-accounting in 32-bit values. This could lead to
spurious warnings, inaccurate accounting, and, in
theory, data loss.
  
Affected: 64-bit platforms. Debug-build (with safemalloc).
At least one buffer larger than 4GB. For potential data
loss, a re-alloc on such a buffer would be necessary.