[Development] Qt5.15 deprecating & Qt6 removing QProcess::setupChildProcess

[Thiago Macieira]

On Tuesday, 18 February 2020 04:11:01 PST Christian Kandeler wrote:
> In qbs, we use it to call setpgid() with the id of the newly created
> process. But I don't understand why that should matter at all: Whether we
> inject the code via an overriden virtual or a std::function is purely a
> question of implementation technique, is it not? How can there possibly be
> a functional difference?

The difference is how you communicate to QProcess that you want to run extra 
code. Right now, you do this by deriving from QProcess and overriding 
setupChildProcess. That means QProcessPrivate::start has no proper way of 
knowing when you did so and must assume that you do want that, preventing us 
from having some optimisations. See the two commits I've just uploaded to 
QProcess 5.15: they are not allowed if user code is running.

I'm asking for a way that we can be certain that you want to run code. It will 
clean up your code and QProcess's. And if we like it, we can have a flag 
saying "my function is async-signal-safe too", which will allow the 
optimisations and the use code.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel System Software Products