QBitArray: avoid overflow in storage-to-size calculations

Unlike other containers, a QBitArray's size() is not limited by
storage, but, esp. on 32-bit platforms, its size_type: A INT_MAX
size() QBitArray only requires 256MiB of storage.

So we can't rely on "won't happen in practice" here and need to avoid
the potential UB (signed overflow) in the (d.size() * 8 - *d.data())
storage-to-logical-size calculation by using unsigned arithmetic.

Use the opportunity to Extract Method adjust_head_and_tail(),
centralizing the bit fiddling.

Pick-to: 6.7 6.6 6.5 6.2 5.15
Change-Id: I485eafdf3ce2087a81c683672ff98a43f97c9968
Reviewed-by: Qt CI Bot <[email protected]>
Reviewed-by: Thiago Macieira <[email protected]>

0 files changed, 0 insertions, 0 deletions