[Qt-interest] static linking

[Malyushytsky, Alex]

Sorry for later correction:

>>  QT4 can be built only with Static CRTs, even if you build it statically .

Should be read as

.... QT4 can be built only with Dynamic CRTs, even if you build it statically .


From: qt-interest-bounces at trolltech.com [mailto:qt-interest-bounces at trolltech.com] On Behalf Of Malyushytsky, Alex
Sent: Friday, May 29, 2009 7:20 PM
To: qt-interest at trolltech.com
Subject: Re: [Qt-interest] static linking

On the Windows you have to make sure that QT, all your static libraries,
and everything else linked to your application using the same C runtime libraries (CRT).
I am not sure about other compilers but if you are using any of Microsoft VC,
QT4 can be built only with Static CRTs, even if you build it statically .

So you have no choice, but build your static libraries with Dynamic CRTs.

As soon you done it, and all static/dynamic libraries are linked to the same (don't mix debug and release either) dynamic CRT libs, you should have no problem to build anything.


Best regards,
Alex




From: qt-interest-bounces at trolltech.com [mailto:qt-interest-bounces at trolltech.com] On Behalf Of Linda Maria
Sent: Tuesday, May 26, 2009 7:39 AM
To: qt-interest at trolltech.com
Subject: [Qt-interest] static linking

Hi all

I want to statically link my own libs, however, still dynamically linking against Qt. When I do this I get undefined reference error. Well, it is clear that the compiler is not finding my libsomename.a file, however, if I compile my library dynamically the compiler has no problem finding somename.dll file.

-I am working with QT 4.5
-I am working on Windows with Qt Creator

Example .pro files are as folow:

lib pro file:
QT -= gui

TARGET = hello_world_lib

TEMPLATE = lib

CONFIG += staticlib

DEFINES += HELLO_WORLD_LIB_LIBRARY

SOURCES += helloworld.cpp

HEADERS += helloworld.h\

hello_world_lib_global.h



app pro file:

TARGET = hello_world

TEMPLATE = app

INCLUDEPATH += ..\hello_world_lib

CONFIG += static

LIBS += -L..\hello_world_lib\debug -lhello_world_lib

TARGETDEPS += ..\hello_world_lib\debug\libhello_world_lib.a

SOURCES += main.cpp \

mainwindow.cpp \

helloworlddialog.cpp

HEADERS += mainwindow.h \

helloworlddialog.h

FORMS += mainwindow.ui \

helloworlddialog.ui \

helloworlddialog.ui



ld output is:

debug/mainwindow.o(.text+0x1bd): In function `ZN10HelloWorld10MainWindowC2EP7QWidget':

C:/Documents and Settings/es030699/My Documents/Qt/hello_world/mainwindow.cpp:15: undefined reference to `_imp___ZN13HelloWorldLib10HelloWorld10getMessageEv'

debug/mainwindow.o(.text+0x3cb): In function `ZN10HelloWorld10MainWindowC1EP7QWidget':

C:/Documents and Settings/es030699/My Documents/Qt/hello_world/mainwindow.cpp:15: undefined reference to `_imp___ZN13HelloWorldLib10HelloWorld10getMessageEv'

collect2: ld returned 1 exit status

mingw32-make.exe[1]: *** [debug\hello_world.exe] Error 1

C:\MinGW\bin\mingw32-make.exe: *** [debug] Error 2

Exited with code 2.

Error while building project hello_world

When executing build step 'Make'



Notice the line

CONFIG += staticlib

in the lib pro file tellst the compiler to create libhello_world_lib.a to statically link agains, and not to create hello_world_lib.dll. I thought the compiler should automatically find out that only a static library is provided and link against it.



Can someone please help me with this?

Thanks,

Linda Maria


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