[Development] Requesting forward BC exception for QtWaylandCompositor in 6.2 and 5.15

Lars Knoll lars.knoll at qt.io
Thu Feb 17 09:01:52 CET 2022

> On 16 Feb 2022, at 18:10, Thiago Macieira <thiago.macieira at intel.com> wrote:
> On Tuesday, 15 February 2022 07:54:07 PST Marc Mutz wrote:
>> https://bugreports.qt.io/browse/QTBUG-100845
>> The QWaylandBufferRef class has a very annoying bug in that its relational
>> operators cannot compare `const` objects (only on the RHS). That's because
>> these operators are implemented as members, but are not const. Since
>> they're not const, they cannot be called with a const LHS...
> By the way, how often is this done? What's the exposure in the real world?

Wayland Compositor is not the most often used module in Qt. I think most users are on embedded devices. That also means I wouldn’t be overly concerned about a FW BC break in that module. Still it’s good if we can avoid it.
> The pre-6.3 implementation could be #if __cplusplus <= 20200000

That could actually be a solution for 6.2. We keep the old API if you compile in C++17 mode and only enable the new methods in C++20 mode. Requires a bit of work on our side to make sure the symbols are in the libraries as required, but otherwise it’s basically about what we expose in the header.


> -- 
> Thiago Macieira - thiago.macieira (AT) intel.com
>  Software Architect - Intel DPG Cloud Engineering
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