Can not create/use DLL

[JacobNovitsky]

Please confirm if guides under the link is still relevant
https://www.youtube.com/watch?v=ZewJ4iHQvXY
https://www.youtube.com/watch?v=9JTooLxhmC0
! Screenshot from 2023-09-26 02-25-15.png

[Paul Colby]

Hi @JacobNovitsky, can you show us the contents of MyLib.pro and useDll.pro?

[SGaist]

Hi,

The Qt documentation has a page dedicated to that.

[JacobNovitsky]

@Paul-Colby hi there :)

SGaist still, I could not find answer to my question :)
please guide me

[SGaist]

@JacobNovitsky please show the content of the files requested by @Paul-Colby.

[JacobNovitsky]

@SGaist sorry, just woke up :)

MyLib.pro

TEMPLATE = lib
DEFINES += MYLIB_LIBRARY

CONFIG += c++17

You can make your code fail to compile if it uses deprecated APIs.

In order to do so, uncomment the following line.

#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0

SOURCES +=
mylib.cpp

HEADERS +=
MyLib_global.h
mylib.h

Default rules for deployment.

unix {
target.path = /usr/lib
}
!isEmpty(target.path): INSTALLS += target

useDll.pro
TEMPLATE = app
CONFIG += console c++17
CONFIG -= app_bundle
#CONFIG -= qt

QT += core

QT += gui
#QT += qapplication
QT += widgets quick

SOURCES +=
main.cpp

[Paul Colby]

Hi @JacobNovitsky ,

Your userDll.pro file appears to be missing a LIBS += line that would be pointing the the build output of the MyLib.pro file (ie the *.so files).

See the end of this page for some inspiration, ie this bit:

win32:CONFIG(release, debug|release): LIBS += -L$$OUT_PWD/../../../projects/mylib/release/ -lmylib
else:win32:CONFIG(debug, debug|release): LIBS += -L$$OUT_PWD/../../../projects/mylib/debug/ -lmylib
else:unix: LIBS += -L$$OUT_PWD/../../../projects/mylib/ -lmylib
INCLUDEPATH += $$PWD/../../../projects/mylib
DEPENDPATH += $$PWD/../../../projects/mylib
win32:CONFIG(release, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../../../projects/mylib/release/mylib.lib
else:win32:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../../../projects/mylib/debug/mylib.lib
else:unix: PRE_TARGETDEPS += $$OUT_PWD/../../../projects/mylib/libmylib.a

Alternatively, since this seems to be a new project, I'd highly recommend you use cmake instead.

Cheers.

[JacobNovitsky]

@Paul-Colby I need to make DLL for my project build with qmake, but thanks for pointing out

should I add to MyLib.pro lines below?

win32:CONFIG(release, debug|release): LIBS += -L$$OUT_PWD/../../../projects/mylib/release/ -lmylib
else:win32:CONFIG(debug, debug|release): LIBS += -L$$OUT_PWD/../../../projects/mylib/debug/ -lmylib
else:unix: LIBS += -L$$OUT_PWD/../../../projects/mylib/ -lmylib
INCLUDEPATH += $$PWD/../../../projects/mylib
DEPENDPATH += $$PWD/../../../projects/mylib
win32:CONFIG(release, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../../../projects/mylib/release/mylib.lib
else:win32:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../../../projects/mylib/debug/mylib.lib
else:unix: PRE_TARGETDEPS += $$OUT_PWD/../../../projects/mylib/libmylib.a

[jsulm]

@JacobNovitsky said in Can not create/use DLL:

should I add to MyLib.pro lines below?

No, to userDll.pro as @Paul-Colby wrote

[JacobNovitsky]

@jsulm great, ty

build folder
home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
source files folder
/home/supernova/MyLib

I'm I correct:
"If I use Ubuntu, I can somehow ignore win32 lines and keep it as in asample -> rest to be amended EXACTlLY like that".

win32:CONFIG(release, debug|release): LIBS += -L$$OUT_PWD/../../../projects/mylib/release/ -lmylib
else:win32:CONFIG(debug, debug|release): LIBS += -L$$OUT_PWD/../../../projects/mylib/debug/ -lmylib
else:unix: LIBS += -L$$OUT_PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug -lmylib
INCLUDEPATH += $$PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
DEPENDPATH += $$PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
win32:CONFIG(release, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../../../projects/mylib/release/mylib.lib
else:win32:CONFIG(debug, debug|release): PRE_TARGETDEPS += $$OUT_PWD/../../../projects/mylib/debug/mylib.lib
else:unix: PRE_TARGETDEPS += $$OUT_PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug

Please confirm, big thanks in advance

[jsulm]

@JacobNovitsky If you don't plan to build for Windows then you can remove all the win32 lines, but don't forget to alter other lines (like removing else:).

[JacobNovitsky]

@jsulm is this correct?

LIBS += -L$$OUT_PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug -lmylib
INCLUDEPATH += $$PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
DEPENDPATH += $$PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
PRE_TARGETDEPS += $$OUT_PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug

Not sure If i need to include project source files, if need please advise where to include

[jsulm]

@JacobNovitsky said in Can not create/use DLL:

Not sure If i need to include project source files

If you want to link against a pre build lib then of course you do not have to include the lib sources in the project which links against it.

[JacobNovitsky]

just delete both projects and created new

pro:

QT -= gui

TEMPLATE = lib
DEFINES += MYLIB_LIBRARY

CONFIG += c++17

You can make your code fail to compile if it uses deprecated APIs.

In order to do so, uncomment the following line.

#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0

SOURCES +=
mylib.cpp

HEADERS +=
MyLib_global.h
mylib.h

LIBS += -L$$OUT_PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug -lmylib

INCLUDEPATH += $$PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
DEPENDPATH += $$PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
PRE_TARGETDEPS += $$OUT_PWD/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug

Default rules for deployment.

unix {
target.path = /usr/lib
}
!isEmpty(target.path): INSTALLS += target

compile output:
:-1: error: No rule to make target '/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug', needed by 'libMyLib.so.1.0.0'. Stop.

path correct, supernova@supernova-BOHB-WAX9:~/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug$ ls
libMyLib.so libMyLib.so.1.0 Makefile
libMyLib.so.1 libMyLib.so.1.0.0 mylib.o

please assist

[JacobNovitsky]

any ideas how to fix that?
compile output:
:-1: error: No rule to make target '/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug', needed by 'libMyLib.so.1.0.0'. Stop.

[SGaist]

Remove $$PWD from the corresponding lines.

Side question: are you going to use that library in any other project ?

[JacobNovitsky]

@SGaist not this, but after I learn how to use this, I gonna use it, for sure

[JacobNovitsky]

@SGaist side question too :)
where can I read about QMAKE?

[SGaist]

In the qmake manual

[JacobNovitsky]

Libtest.pro
QT = core

CONFIG += c++17 cmdline

You can make your code fail to compile if it uses deprecated APIs.

In order to do so, uncomment the following line.

#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0

SOURCES +=
main.cpp

Default rules for deployment.

qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

LIBS +=/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
INCLUDEPATH +=/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
DEPENDPATH +=/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug
PRE_TARGETDEPS +=/home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug

MyLib.pro

QT -= gui

TEMPLATE = lib
DEFINES += MYLIB_LIBRARY

CONFIG += c++17

You can make your code fail to compile if it uses deprecated APIs.

In order to do so, uncomment the following line.

#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0

SOURCES +=
mylib.cpp

HEADERS +=
MyLib_global.h
mylib.h

Default rules for deployment.

unix {
target.path = /usr/lib
}
!isEmpty(target.path): INSTALLS += target

:-1: error: cannot find /home/supernova/build-MyLib-Desktop_Qt_6_2_4_GCC_64bit-Debug: file format not recognized

How to fix error above? There is still no DLL, if I comply with syntax, shall I get dll?