Why can't I use -J4 anymore in Build Steps Additional Arguments ?

elpidiovaldez5

I always use -J4 as an additional build option to get faster build times by using 4 threads. Suddenly I can't use it any more. I have just installed Qtcreator 4.1.0. Perhaps that is the culprit, but surely this is still possible.

If I add the option the build does not start and just shows a red progress bar. I am sure I am doing something really obviously wrong, but I can't see it ! The following message is printed:

02:06:18: Running steps for project Robot...
02:06:18: Starting: "/usr/lib/x86_64-linux-gnu/qt5/bin/qmake" /home/paul/Documents/C++/Robot2016/Robot/Robot/Robot.pro -spec linux-g++-64 CONFIG+=debug -J4
Usage: /usr/lib/x86_64-linux-gnu/qt5/bin/qmake [mode] [options] [files]

QMake has two modes, one mode for generating project files based on
some heuristics, and the other for generating makefiles. Normally you
shouldn't need to specify a mode, as makefile generation is the default
mode for qmake, but you may use this to test qmake on an existing project

Mode:
  -project       Put qmake into project file generation mode
                 In this mode qmake interprets files as files to
                 be built,
                 defaults to *; *; *; *.ts; *.xlf; *.qrc
                 Note: The created .pro file probably will 
                 need to be edited. For example add the QT variable to 
                 specify what modules are required.
  -makefile      Put qmake into makefile generation mode (default)
                 In this mode qmake interprets files as project files to
                 be processed, if skipped qmake will try to find a project
                 file in your current working directory

Warnings Options:
  -Wnone         Turn off all warnings; specific ones may be re-enabled by
                 later -W options
  -Wall          Turn on all warnings
  -Wparser       Turn on parser warnings
  -Wlogic        Turn on logic warnings (on by default)
  -Wdeprecated   Turn on deprecation warnings (on by default)

Options:
   * You can place any variable assignment in options and it will be     *
   * processed as if it was in [files]. These assignments will be parsed *
   * before [files].                                                     *
  -o file        Write output to file
  -d             Increase debug level
  -t templ       Overrides TEMPLATE as templ
  -tp prefix     Overrides TEMPLATE so that prefix is prefixed into the value
  -help          This help
  -v             Version information
  -after         All variable assignments after this will be
                 parsed after [files]
  -norecursive   Don't do a recursive search
  -recursive     Do a recursive search
  -set <prop> <value> Set persistent property
  -unset <prop>  Unset persistent property
  -query <prop>  Query persistent property. Show all if <prop> is empty.
  -cache file    Use file as cache           [makefile mode only]
  -spec spec     Use spec as QMAKESPEC       [makefile mode only]
  -nocache       Don't use a cache file      [makefile mode only]
  -nodepend      Don't generate dependencies [makefile mode only]
  -nomoc         Don't generate moc targets  [makefile mode only]
  -nopwd         Don't look for files in pwd [project mode only]
***Unknown option -J4
02:06:18: The process "/usr/lib/x86_64-linux-gnu/qt5/bin/qmake" exited with code 1.
Error while building/deploying project Robot (kit: Desktop)
When executing step "qmake"
02:06:18: Elapsed time: 00:00.

Paul Colby

Hi @elpidiovaldez5

As far as I know, qmake has never had support for running multiple jobs in parallel. I wouldn't really expect it to either, since its simply a build script generator (albeit a pretty advanced one). It's actually the make (most platforms) or nmake (Windows) commands that control the builds, so its those commands that you'd want to use -j4 (or equivalent) with.

For example, on Linux:

qmake
make -j4

or on Windows:

qmake
nmake /MP4

Cheers.

jsulm

@elpidiovaldez5 To add to @Paul-Colby : shouldn't it be -j4 (not -J4)?

elpidiovaldez5

@jsulm @Paul-Colby

Both of you are right, but the stupid thing, that I could not see, was that I was using the qmake arguments field in QtCreator instead of the make arguments field.

Thanks very much.