QMake -- OBJ_DIR behaves differently on Linux than on Windows

[Robert Hairgrove]

Using Qt 5.12.9 on Windows and Ubuntu Linux 18.04...

I want to have all of my temporary files written to different places depending on whether I am doing a debug or release build.

On Linux, this works as expected (in my .pro file):

  OBJECTS_DIR = ./.obj
  MOC_DIR     = ./.moc
  RCC_DIR     = ./.qrc
  UI_DIR      = ./.ui

My default build directory is set to the following string in "Tools/Build & Run/Default Build Properties":

build/%{JS: Util.asciify(%{BuildConfig:Name})}

So when I do debug and release builds on Linux, I see the following directory structure:

MyProject
⌙  MyProject.pro
⌙  <other directories...>
⌙  build
    ⌙ Debug
        ⌙.obj
        ⌙.moc
        ⌙.qrc
        ⌙.ui
    ⌙ Release
        ⌙.obj
        ⌙.moc
        ⌙.qrc
        ⌙.ui

But on Windows, qmake always puts these directories one level ABOVE where I actually want to have them, i.e.:

MyProject
⌙  MyProject.pro
⌙  <other directories...>
⌙  build
    ⌙.obj
    ⌙.moc
    ⌙.qrc
    ⌙.ui
⌙  Debug
⌙  Release

This leads to numerous problems with DLLs on Windows since in order to build at all, I have to do a clean build before changing the configuration from Debug to Release.

Therefore, in my .pro file, I have the following:

unix {
  OBJECTS_DIR = ./.obj
  MOC_DIR     = ./.moc
  RCC_DIR     = ./.qrc
  UI_DIR      = ./.ui
}
win32 {
  CONFIG(debug) {
    OBJECTS_DIR = ./Debug/.obj
    MOC_DIR     = ./Debug/.moc
    RCC_DIR     = ./Debug/.qrc
    UI_DIR      = ./Debug/.ui
  }
  CONFIG(release) {
    OBJECTS_DIR = ./Release/.obj
    MOC_DIR     = ./Release/.moc
    RCC_DIR     = ./Release/.qrc
    UI_DIR      = ./Release/.ui
  }
}

Now, when I build on Windows, the temporary directories are placed under the Release subfolder, even when building in Debug mode!

I must be missing something?

[SGaist]

Hi,

If memory serves well, this is an idiosyncrasie from Visual Studio that qmake can essentially do nothing about.

That said, it has become pretty unusual to do it that way since out of source builds have become standard. If you really want to move these build artifacts to specific folders, your should use OUT_PWD. This way you should start at the top of the build folder.

[Robert Hairgrove]

@SGaist Thank you for pointing out the OUT_PWD variable.

[EDIT: this is using MSVC 2015 on Windows 10, BTW]

Turns out that one of the problems I was having was from using CONFIG(debug) and CONFIG(release) instead of:

CONFIG(debug, debug|release) {
...
}
CONFIG(release, debug|release) {
...
}

Even so, In the meantime, I have tried lots of things, but qmake and/or MSVC seem to ignore everything except for the original way I did it for Linux, i.e.:

 OBJECTS_DIR = ./.obj
 MOC_DIR     = ./.moc
 RCC_DIR     = ./.qrc
 UI_DIR      = ./.ui

If I have defined my default build directory as ./build in the Tools/Options settings and .build/Debug and build/Release in the project's build settings, then I get the following structure (which I can live with since it separates the temporary artifacts created in the two configurations debug and release):

<project directory>
  ↪build
   .qstash file
   Makefile
   Makefile.Debug
   Makefile.Release
   .rc file
    ↪Debug
      ⌙.obj
      ⌙.moc
      ⌙.qrc
      ⌙.ui
      ⌙debug   <== has .EXE file
      ⌙release <== always empty
    ↪Release
      ⌙.obj
      ⌙.moc
      ⌙.qrc
      ⌙.ui
      ⌙debug   <== always empty
      ⌙release <== has .EXE file

Certainly not as elegant as on Linux, but it's not a big deal. At least this way I can do a quick clean and delete the stash file as well (which it never does when running "Clean" from within Qt Creator).

Marking this now as SOLVED.