[Development] Binary incompatible change in QtConcurrent - was - Re: Qt 5.15.6 Opensource released

[Sona Kurazyan]

I've created a revert commit for 5.15, see https://codereview.qt-project.org/c/qt/tqtc-qtbase/+/431686.

Best regards,
Sona

> -----Original Message-----
> From: Development <development-bounces at qt-project.org> On Behalf Of
> Thiago Macieira
> Sent: Thursday, September 8, 2022 11:23 PM
> To: development at qt-project.org
> Subject: Re: [Development] Binary incompatible change in QtConcurrent -
> was - Re: Qt 5.15.6 Opensource released
> 
> On Thursday, 8 September 2022 14:06:24 PDT Albert Astals Cid wrote:
> > Should we restore those symbols or just accept that Qt 6 broke BC a
> > year ago and no one realized so why bring the symbols back?
> 
> The commit message says
> 
>     Remove the dead code for blocking methods from QtConcurrent
> 
>     After 79fd1cb2c631b6084bf10874205d27f5b53c907a the methods for
> running
>     QtConcurrent algorithms in the blocking mode aren't used anymore. Since
>     ThreadEngineBase and ThreadEngineStarter classes aren't meant to be
> used
>     externally, it should be fine to remove startBlocking() methods now.
> 
> ThreadEngineBase is used only by ThreadEngine, plus its static
> ThreadEngineBase::threadPool is used by
> IterateKernel::forThreadFunction().
> But ThreadEngine is a template class deriving from ThreadEngineBase, and
> IterateKernel is a template class deriving from ThreadEngine and that is in
> turn a base class for a lot of other classes.
> 
> Therefore, ThreadEngineBase is used by user code, only indirectly.
> 
> So the question is whether the removed function was ever callable in
> QtConcurrent from 6.0 to 6.3. The commit this commit refers to landed in 6.0.
> So if the commit message is correct, then there's no problem in Qt 6, because
> if something still called this function, it would have broken in this commit.
> 
> According to the Git log, 1bf75f2a661c05c7f1126187310d7df3f9704af5 is the
> only commit since Git tag v6.0.0 that touches a line that mentions
> "startBlocking".
> Therefore, there is no BC problem in Qt 6.
> 
> --
> Thiago Macieira - thiago.macieira (AT) intel.com
>   Cloud Software Architect - Intel DCAI Cloud Engineering
> 
> 
> 
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