[Development] INTEGRITY

Mutz, Marc marc at kdab.com
Thu Sep 19 11:18:26 CEST 2019

On 2019-09-19 10:56, Lars Knoll wrote:
>> 4. drop Integrity support (or update to a newer version) ASAP (for
>> Qt 5.15 if not 5.14).
>  This is a bit black and white. You’re proposing to drop all of
> INTEGRITY because you’re not willing to work around things on that
> platform for one patch that is in principle a pure cleanup patch doing
> internal refactoring. It wouldn’t be too difficult (though maybe not
> very nice looking though) to keep the old code for INTEGRITY only.
> It’s been tested and we know it works.
> We’ve been applying workarounds for missing support for some C++11
> features in other toolchains/compilers as well. We kept the Atomic
> implementations for MSVC around for exactly the same reasons.

That may work for the series of patches that implements QWaitCondition 
using std::condition_variable, which, indeed, is just a cleanup patch.

But it helps nothing with all the places where we use QWaitCondition in 
Qt implementation and would like to replace it with 
std::condition_variable + std::mutex, because, as I explained in an 
earlier mail, QWaitCondition is a condition_variabe_any and thus has 
inherently and unavoidably more overhead than condition_variable + 
mutex. There is no justification to add #ifdefs for all the places that 
QWaitCondition is used unconditionally now, so either we don't get the 
order-of-magnitude improvement on our main platform, Windows, or we need 
to introduce a private QtPrivate::condition_variable as an inline 
wrapper around condition_variable + mutex or, for Integrity, 
QWaitCondition + QMutex, which we need to replace once more with 
std::condition_variable + mutex if Integrity is fixed. Is it worth it, 
for a buggy platform that's in the process of being fixed? I'm not sure 
it would be...

In addition, as Peppe noticed, this is not the first time Integrity has 
shown up as a problematic platform, and it now is so far behind all the 
other supported platforms, as well as its own claim of conformance, that 
the question must be asked why it's still supported.


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