[Development] Asking for a FF exception for ICU based QStringConverter

Lars Knoll lars.knoll at qt.io
Wed Jun 8 17:02:34 CEST 2022

Given that the change doesn’t interfere with existing functionality, this is ok. But please try to finish and get the change merged as soon as possible.


> On 8 Jun 2022, at 16:17, Fabian Kosmale <fabian.kosmale at qt.io> wrote:
> Hi,
> unfortunately, we did not manage to get a QStringConverter backend based on ICU into Qt in time for FF
> (https://codereview.qt-project.org/c/qt/qtbase/+/393373). This is a feature strongly requested by KDE as an enabler
> for their KDE Frameworks 6 port [1] and from various users in APAC, where non-UTF codecs like Shift JIS  still have some
> popularity.
> What remains to be done:
> - There are concerns that mixing Qt versions might lead to an unbounded memory leak with the current implementation.
>  I don't think that's actually the case (but if it is, then we need a different enough approach that this most likely has to be
>  deferred to Qt 6.5 at least).
> -  Testing uncovered that there's an issue with writing out replacement characters, causing infinite recursion under certain
>    circumstances. That needs to be fixed, but should hopefully be easy by checking and mirroring how ICU's own replacement
>    callback works.
> - Thiago (rightfully) requested more test cases; I'm cautiously optimistic that those won't uncover any further issues.
> Impact on other parts of Qt and 6.4 API review
> - The base patch will not introduce any new public API, it just extends what is possible with the existing API.
> - The follow-up patch will introduce one new function; and make use of the new ICU backend in a few places in Qt, which
>   before would have rejected the incoming data.
> Expected additionally needed time:
> I expect that the remaining work can be completed by the end of next week.
> Given the above, would it be possible to grant a feature freeze exemption until end of next week for this feature?
> Regards,
> Fabian
> [1] KDE has to support legacy codecs in e.g. their text editor(s).
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