How to determine target architecture in qmake project file?

[ChrisW67]

You use a subdirs project. For a simple example project.pro:

TEMPLATE = subdirs
SUBDIRS = foo bar app
CONFIG += ordered  # makes sure libs foo and bar are built before app

TEMPLATE = subdirs
SUBDIRS = foo bar app
CONFIG += ordered  # makes sure libs foo and bar are built before app

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with a source tree like:

- project.pro
+ foo
  - foo.pro
  - a.cpp
  - etc...
+ bar
  - bar.pro
  - b.cpp
  - etc...
+ app
  - app.pro
  - main.cpp
  - mainwindow.cpp
  - etc...

- project.pro
+ foo
  - foo.pro
  - a.cpp
  - etc...
+ bar
  - bar.pro
  - b.cpp
  - etc...
+ app
  - app.pro
  - main.cpp
  - mainwindow.cpp
  - etc...

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The app.pro could reference the libraries:

TEMPLATE = app
TARGET = MyCoolProgram
INCLUDEPATH += ../foo ../bar
LIBS += -L../foo -lfoo
LIBS += -L../bar -lbar
...

TEMPLATE = app
TARGET = MyCoolProgram
INCLUDEPATH += ../foo ../bar
LIBS += -L../foo -lfoo
LIBS += -L../bar -lbar
...

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and a library PRO would look like:

TEMPLATE = lib
TARGET = foo
SOURCES += ...
HEADERS += ...

TEMPLATE = lib
TARGET = foo
SOURCES += ...
HEADERS += ...

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Done from memory, check the qmake manual.