Re: [Development] Qt Compilation Speed

2022-01-03 Thread Lars Knoll
> On 3 Jan 2022, at 16:10, Sérgio Martins wrote: > > On 2022-01-03 13:40, Lars Knoll wrote: >> (...) >> One other possible solution to improve compile times is the hack we >> used 15 years ago in KDE, where we grouped many .cpp files into one >> compilation unit. There’s however a balance neede

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Thiago Macieira
On Monday, 3 January 2022 12:10:04 -03 Sérgio Martins via Development wrote: > It does make incremental builds slower, as then you need to recompile > the entire amalgamation. For this reason I don't think > it's a silver bullet. It's not. Unless we're careful with the code we write, merging two .

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Sérgio Martins via Development
On 2022-01-03 13:40, Lars Knoll wrote: (...) One other possible solution to improve compile times is the hack we used 15 years ago in KDE, where we grouped many .cpp files into one compilation unit. There’s however a balance needed here, as it reduces the efficiency of -j, but maybe compiling 4-8

Re: [Development] Nominating Morten Sørvig as maintainer of high-DPI

2022-01-03 Thread Richard Gustavsen
+1 Richard On 20 Dec 2021, at 16:35, Tor Arne Vestbø mailto:tor.arne.ves...@qt.io>> wrote: Hello all, I’d like to nominate Morten Sørvig as maintainer of high-DPI in the Qt Project [1]. Morten has been instrumental in the development of Qt’s high-DPI support, and has been the de-factor main

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Sérgio Martins via Development
On 2022-01-03 08:43, Marc Mutz wrote: Hi, The Qt Creator folks have noted that compilation of Qt projects against Qt 6.2 is sometimes almost twice as slow as it was in 5.15: https://bugreports.qt.io/browse/QTBUG-97601 While we have some ideas where this may come from (including more std headers

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Thiago Macieira
On Monday, 3 January 2022 10:40:42 -03 Lars Knoll wrote: > One other possible solution to improve compile times is the hack we used 15 > years ago in KDE, where we grouped many .cpp files into one compilation > unit. There’s however a balance needed here, as it reduces the efficiency > of -j, but m

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Thiago Macieira
On Monday, 3 January 2022 11:05:25 -03 Philippe wrote: > > The change to C++17 makes a huge difference too, regardless of PCH. That > > #include in qglobal.h adds up to 300 ms in each build without > > PCH, and a considerable amount with it too. And it gets worse with C++20 > > and ranges. > I did

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Philippe
> The change to C++17 makes a huge difference too, regardless of PCH. That > #include in qglobal.h adds up to 300 ms in each build without > PCH, > and a considerable amount with it too. And it gets worse with C++20 and > ranges. I did not notice any sensitive change when switching to C++20 (

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Lars Knoll
On 3 Jan 2022, at 14:21, Thiago Macieira mailto:thiago.macie...@intel.com>> wrote: On Monday, 3 January 2022 05:43:53 -03 Marc Mutz wrote: Hi, The Qt Creator folks have noted that compilation of Qt projects against Qt 6.2 is sometimes almost twice as slow as it was in 5.15: https://bugreports.

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Thiago Macieira
On Monday, 3 January 2022 08:09:39 -03 Ulf Hermann wrote: > d, We used to build at least Qt itself with PCH by default. Why did we > change the default? I don't know about you, but I disabled PCH when I started using icecream for distributed compiling about 5 years ago. It's incompatible with PCH

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Thiago Macieira
On Monday, 3 January 2022 05:43:53 -03 Marc Mutz wrote: > Hi, > > The Qt Creator folks have noted that compilation of Qt projects against Qt > 6.2 is sometimes almost twice as slow as it was in 5.15: > https://bugreports.qt.io/browse/QTBUG-97601 > > While we have some ideas where this may come fr

Re: [Development] Qt Compilation Speed

2022-01-03 Thread Ulf Hermann
a) do we care I care. b) what metrics should we use to define success? I don't care whether it uses PCH or not. It should do the fastest thing by default. So, my metric is "time it takes to build " on my machine. My favorite project is qtdeclarative, but I also build other things. c, Wh

[Development] Qt Compilation Speed

2022-01-03 Thread Marc Mutz
Hi, The Qt Creator folks have noted that compilation of Qt projects against Qt 6.2 is sometimes almost twice as slow as it was in 5.15: https://bugreports.qt.io/browse/QTBUG-97601 While we have some ideas where this may come from (including more std headers, qmetatype compile-time typename con