[Development] What's our policy on changing the result of qHash(T, 0) between major releases?

[Giuseppe D'Angelo]

Il 03/02/24 22:08, Thiago Macieira ha scritto:
> But what about a zero seed? It's what we call a "deterministic hashing". We
> have changed the algorithms on .0 releases (in both 5.0 and 6.0 for QString).

I don't think it means "deterministic" in the sense that the output will 
never change across Qt versions. It just means deterministic across 
multiple runs of the very same application using the very same Qt version.

When you disable QHash seeding, the choice of making the seed equal to 0 
is just "a choice"; we could make it 42 or 0xF0CACC1A, for what is 
worth. qHash can still change its output at any time across Qt versions 
and software should never ever rely on that.

My 2 c,

-- 
Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
KDAB - Trusted Software Excellence

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 4244 bytes
Desc: Firma crittografica S/MIME
URL: <http://lists.qt-project.org/pipermail/development/attachments/20240204/e1552364/attachment.bin>