The lengthHelperContainer() implementation for sizeof(Char) == 1 case
is using qstrnlen() for the non-constexpr case.
qstrnlen() is an inline function which is effectively a nullptr check
and a memchr() call.
For some reason, on MSVC this combination resulted in very slow
compilation for the user projects, where each call to
QObject::setObjectName() was hitting this codepath.
Fix it by replacing the qstrnlen() call with strnlen_s() for MSVC.
It seems that for now all versions of MSVC are affected. However,
introduce a new Q_COMPILER_SLOW_QSTRNLEN_COMPILATION definition,
which will allow us to check for the compiler version later on.
For now this definition is set for all MSVC versions unconditionally.
Fixes: QTBUG-124376
Pick-to: 6.7 6.7.1
Change-Id: Id769bef1e950ffa756acf7af39d362fd8b112019
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
d849cb80a4