[Interest] Qt 6 is much more faster to compile from source

[Thiago Macieira]

On Tuesday, 7 September 2021 10:57:38 PDT Konstantin Tokarev wrote:
> If generated makefiles were non-recursive, it would be even faster.

Right. There are a couple of points during the build that the processor is 
idle waiting for something to finish building before the next thing can start. 
There's a critical path dependency chain going through the bootstrap library, 
moc, then QtCore that affects both buildsystems. There's no workaround for 
that.

qtbase/src's qmake file was hand-rolled to make sure that we did have the 
minimum number of dependencies in the critical path. That extends to bundled, 
third-party sources if you need them. All of that had to be manually-
maintained (see [1]). With CMake, we got that for free, since it resolves the 
dependencies on its own.

[1] https://code.qt.io/cgit/qt/qtbase.git/log/src/src.pro?h=5.15

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