Shared code in subdirs template?



  • Currently I'm making a project which will finally generate two executables, (and of course) with qmake.
    They share some code, so I put the shared part to a directory called "common", just under the root directory.
    Code for these two executables are also put into separate directories under the root dir; one called "game", the other one called "editor".

    I don't know how to use code in the "common" directory; I want to compile the shared code directly into these executables, so setting its template to "lib" and generate shared objects may not be a good solution for me.



  • Generate a static library instead.



  • Er... I mean I don't want to use .so or .dll files.



  • "Static libraries":http://en.wikipedia.org/wiki/Static_library are libraries that are linked into your program. You won't be needing a dll or so in that case.



  • Ah-oh. Awkward. Thanks.



  • Well, I successfully generated libcommon.a in common/; but I don't know how to make the final executables use it.

    I tried to insert these lines into the .pri files, but it seems not working.
    DEPENDPATH += ../common/
    INCLUDEPATH += ../
    POST_TARGETDEPS += ../common/libcommon.a

    Here is the error log:
    g++ -Wl,-O1 -Wl,-rpath,/usr/lib64/qt4 -o ../saye build/main.o build/Saye.o build/GameWindow.o build/SayeMainWindow.o build/moc_Saye.o build/moc_GameWindow.o build/moc_SayeMainWindow.o -L/usr/lib64/qt4 -L/usr/X11R6/lib -lSimpleAV_SDL -lSimpleAV sdl-config --libs -lSDL_mixer -L/usr/local/lib -pthread -lavformat -lavcodec -ldl -lasound -lbz2 -lz -lswscale -lavutil -lm -lQtXml -L/usr/lib64 -L/usr/lib64/qt4 -lQtOpenGL -L/usr/X11R6/lib -lQtGui -lQtCore -lgthread-2.0 -lrt -lglib-2.0 -lGLU -lGL -lpthread
    build/Saye.o: In function Saye::openProject()': Saye.cpp:(.text+0x730): undefined reference toSayaMap::SayaMap(QString)'
    Saye.cpp:(.text+0x7b8): undefined reference to `SayaMap::dump()'
    collect2: ld returned 1 exit status
    make: *** [../saye] Error 1

    The SayaMap class is defined in common/. Almost everything works well; this issue happens when linking the object files.



  • Something like
    @
    LIBS+=-L/path/to/common/libs -lcommon
    @

    Adding the path to common libs is only necessary if they're not already in your search path. You could try with -lcommon first to see if it has the desired effect already.



  • Nmmm... In fact I tried
    @LIBS += ../common/libcommon.a@
    Very ugly, but works.

    But here comes another question: what if we later updated common? Code used it should be recompiled, but make will not think it needs to do so.

    Maybe I should switch back to shared libraries.



  • I'm not sure how to handle it directly with qmake, but you can always touch a header file (Saye.h for example) to force a rebuild & relink. Of course just a relink only would be nicest.



  • This worked for me on unix/linux:

    @
    PRE_TARGETDEPS = ../common/libcommon.a
    @

    This ensures that the final target is rebuilt, once libcommon.a has changed.



  • So it will be different on Windows?



  • [quote author="wecing" date="1319138207"]So it will be different on Windows?[/quote]

    For MinGW this should work too, as it's a gnu toolchain. It should work for the visual studio toolchain together with Qt Creator as IDE too.

    I don't know if it works with full Visual Studio usage (including the IDE/GUI).


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