Both format strings > 2GiB, as well as result strings > 2Gi characters
were affected by the append_utf8() helper function being left unported
from int to qsizetype.
There were actually two bugs in that 5LOC function:
1. The len argument was an int, but the caller feeds a difference of
pointers (even explicitly cast to qsizetype) to the function, so
any stretch of verbatim text > 2GiB in the format would cause the
output string to be corrupted.
2. If the result string was already > 2Gi characters in size, a call
to append_utf8() would truncate it mod INT_MAX, because the
string's size() was stored in an int variable and the used in a
resize() call.
Pick-to: 6.4 6.3 6.2
Task-number: QTBUG-103531
Change-Id: I0a09d27b7782093d3f8ea17bb621ff8dad375072
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
f73833809b