Looking for good explanation of creation process of Static Lib and it's Test App

sitesv

Hi!
Could you please explain about the creation of static lib with a test app for both OS like Linux and Windows with the right relative paths? I'm in a mess. What is work fine in Linux, cannot be recompiled and work in Windows. There is magic with paths, shadow builds and etc.

SGaist

Hi,

Can you show your .pro files ?

gde23

I guess you need to provide a little bit more information.

What make toolkit are you using?
Is the lib in the same project as the executable
What exactly is the problem you have?

sitesv

@SGaist , @gde23
test app pro file:

QT -= gui

CONFIG += c++11 console
CONFIG -= app_bundle

DEFINES += QT_DEPRECATED_WARNINGS

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

win32
{
    CONFIG(release, debug|release){
        LIBS += -L$$PWD/../project1/cpp/dll/mylib/release/ -lmylib
        INCLUDEPATH += $$PWD/../project1/cpp/dll/mylib/release
        DEPENDPATH += $$PWD/../project1/cpp/dll/mylib/release
    }
    CONFIG(debug, debug|release){
        LIBS += -L$$PWD/../project1/cpp/dll/mylib/debug/ -lmylib
        INCLUDEPATH += $$PWD/../project1/cpp/dll/mylib/debug
        DEPENDPATH += $$PWD/../project1/cpp/dll/mylib/debug
    }
}
unix
{
    LIBS += -L$$PWD/../project1/cpp/dll/mylib/ -lmylib
    INCLUDEPATH += $$PWD/../project1/cpp/dll/mylib
    DEPENDPATH += $$PWD/../project1/cpp/dll/mylib
}

Lib Pro file:

QT       -= gui
TARGET = GET_INF_HUB
TEMPLATE = lib
DEFINES += GET_INF_HUB_LIBRARY
DEFINES += QT_DEPRECATED_WARNINGS
SOURCES += \
        mylib.cpp
HEADERS += \
        mylib.h \
        mylib_global.h 
unix {
    target.path = /usr/lib
    INSTALLS += target
}

Static lib added to test app like an external lib.

In Linux test app starts without problems.
In Windows, first of all, I need to uncheck Shadow build in test and lib apps... And after compilation there is an error msg:
main.obj:-1: error: LNK2019: unresolved external symbol __imp__Start referenced in function _main
I have cleaned tmp files and folders... But there is no effect...

SGaist

First thing: are you sure your library is properly statically built on Windows ?

If not, then I would guess you are not properly exporting the symbols from that library hence the missing symbol.

sitesv

@SGaist said in Looking for good explanation of creation process of Static Lib and it's Test App:

First thing: are you sure your library is properly statically built on Windows ?

How I should check this?

SGaist

Are you properly setting the static flag in your library project ? Do you get a .dll when building on Windows ?

sitesv

@SGaist said in Looking for good explanation of creation process of Static Lib and it's Test App:

Are you properly setting the static flag in your library project ? Do you get a .dll when building on Windows ?

Yes. Dll and Lib files are created after building lib.

SGaist

Then your library is not build statically and you are not properly exporting symbols.

For that second part see here.

sitesv

@SGaist thanks. I will recode my lib.

I there any way to debug dynamic/static lib?

SGaist

Sure, use a debug build of your library.

sitesv

@SGaist ones more Q:
But how the same project works in Linux?

SGaist

Because the symbol exportation does not work the same on Linux.

gde23

When you have a library under windows you need to explicitly export the symbols.
On linux it is not necessary because the symbols are managed in another way.

Typically this is done using a preprocessor define that you add at any function / class that you wanna export like (just look it up on stackoverflow)

#ifdef WIN32
    #define DECL_EXPORT __declspec(dllexport)
    #define DECL_IMPORT __declspec(dllimport)
#else
    #define DECL_EXPORT
    #define DECL_IMPORT
#endif

SGaist

@gde23 said in Looking for good explanation of creation process of Static Lib and it's Test App:

When you have a library under windows you need to explicitly export the symbols.
On linux it is not necessary because the symbols are managed in another way.

Typically this is done using a preprocessor define that you add at any function / class that you wanna export like (just look it up on stackoverflow)
#ifdef WIN32
    #define DECL_EXPORT __declspec(dllexport)
    #define DECL_IMPORT __declspec(dllimport)
#else
    #define DECL_EXPORT
    #define DECL_IMPORT
#endif

That is incomplete, The macro to use depend whether you are building the library or using it. See the dedicated chapter in Qt's documentation for a clean way to handle that.

sitesv

@SGaist I checked my code... It is matches to link.
But lib and dll files are created.

Should this code be in pro file:

CONFIG += staticlib

?

So, I have included this string to pro and as a result a lib file only.

Could you please see my test apps? ==> app

gde23

@SGaist You are right. I forgot to mention that part.
@sitesv The dll will be created also if you do not export the symbols. But the exe will not know about the function/class inside the dll so it will not find them.
Did you include the defines as in the description SGaist posted?

sitesv

@gde23 said in Looking for good explanation of creation process of Static Lib and it's Test App:

@SGaist You are right. I forgot to mention that part.
@sitesv The dll will be created also if you do not export the symbols. But the exe will not know about the function/class inside the dll so it will not find them.
Did you include the defines as in the description SGaist posted?

Yes. I checked it. Could you view my code by this link?

UPD: I inserted the line "extern int test();" to main.cpp. And voila!