It was confusing entry capacity with the bucket capacity. The value
maxNumBuckets() returned was the maximum number of entries. This issue
was harmless: we would just fail to cap the maximum to an allocatable
size. But the array new[] in the Data constructors would have capped the
maximum anyway (by way of throwing std::bad_alloc).
So instead of trying to calculate what the maximum bucket count is so we
can cap at that, simplify the calculation of the next power of 2 while
preventing it from overflowing in our calculations. We continue to rely
on new[] throwing when we return count that is larger than the maximum
allocatable.
This commit changes the load factor for QHashes containing exactly a
number of elements that is exactly a power of two. Previously, it would
be loaded at 50%, now it's at 25%. For this reason, tst_QSet::squeeze
needed to be fixed to depend less on the implementation details.
Pick-to: 6.5
Change-Id: I9671dee8ceb64aa9b9cafffd17415f3856c358a0
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
1d167b515e