[Development] Broken RNG on AMD Ryzen CPUs affect QTemporaryFile, Qt IFW

[Edward Welbourne]

On Tue, 18 Feb 2020 19:35:53 +0800
Sze Howe Koh <szehowe.koh at gmail.com> wrote:
>> See https://forum.qt.io/topic/111473/maintenance-tool-error-cannot-open-file-for-writing-no-error/

I note that the code quoted is using rand(); the code in QTemporary file
switched to using QRandomGenerator at 5.10.0; that's what now produces
the "WARNING: RDRND generated:" message reported in one post.

Christian Kandeler (18 February 2020 12:59) replied
> Probably the same as https://bugreports.qt.io/browse/QTBUG-77375.

Fixed in 5.13.0 - the fix added the warning quoted above and takes steps
to ensure we don't rely on the broken HWRNG, presumably falling back to
some pseudo-random alternative.

>> Is this worth a post on the Qt Blog? I foresee many frustrated and
>> confused Ryzen users out there who would benefit from a reminder to
>> update their BIOS.

> I suppose it won't hurt, but I wonder how such a system is usable at
> all...

Which version was this encountered in ?

	Eddy.