Problem with class type for dll

Hi All,

I have been trying to create a shared library using guidelines from the article https://doc.qt.io/qt-5/sharedlibrary.html :

Qt .pro :Attachment 13455

Code:

---

QT       += qml quick core
 
 
TARGET = profile1
TEMPLATE = lib
 
DEFINES += PROFILE1_LIBRARY
 
# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS
 
 
 
# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
 
SOURCES += \
        profile1.cpp
 
HEADERS += \
        profile1.h \
        profile1_global.h 
 
unix {
    target.path = /usr/lib
    INSTALLS += target
}

---

Main header :Attachment 13456

Code:

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#ifndef PROFILE1_GLOBAL_H
#define PROFILE1_GLOBAL_H
 
#include <QtCore/qglobal.h>
 
 
#if defined(PROFILE1_LIBRARY)
#  define PROFILE1SHARED_EXPORT Q_DECL_EXPORT
#else
#  define PROFILE1SHARED_EXPORT Q_DECL_IMPORT
#endif
 
#endif // PROFILE1_GLOBAL_H

---

Header :Attachment 13457

Code:

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#ifndef PROFILE1_H
#define PROFILE1_H
 
 
#include "profile1_global.h"
 
 
class PROFILE1SHARED_EXPORT Profile1
{
 
public:
 
    Profile1();
    void func1();
 
};
 
 
#endif // PROFILE1_H

---

Code : Attachment 13458

Code:

---

#include "profile1.h"
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
 
 
Profile1::Profile1()
{
 
}

---

I keep getting an error for class declaration : class PROFILE1SHARED_EXPORT Profile1 -" variable has incomplete type 'class Q_DECL_EXPORT' "
Thank you in advance for your help.

According to the docs on creating shared libraries, you should be including "<QtCore/QtGlobal>", not "<QtCore/qglobal>".

I have made the change "<QtCore/QtGlobal>"instead of"<QtCore/qglobal>" but nothing changed. I still get the same error. I have to mention that I am using a C++ compiler and the OS is Linux

Well, yeah, if you look at the contents of QtGlobal, it is:

Code:

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#include "qglobal.h"

---

:rolleyes:


But in any case, these export and import macros are only used for building Windows DLLs. They are not used on linux platforms, and are typically #define to be nothing, usually something like this:

Code:

---

#ifdef _WIN32 || _WIN64
    #define Q_DECL_EXPORT __declspec(dllexport)
    #define Q_DECL_IMPORT __declspec(dllimport)
#else
    #define Q_DECL_EXPORT
    #define Q_DECL_IMPORT
#endif

---

So in fact you don't need to put any type of declaration in front of your class names.

Quote:

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Originally Posted by cleopa

I have to mention that I am using a C++ compiler and the OS is Linux

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Posted code compiles and links as-is for me: Linux, GCC 9.3.0, Qt 5.12.8

Code:

---

chrisw@newton:/tmp/tt$ qmake
Info: creating stash file /tmp/tt/.qmake.stash
 
chrisw@newton:/tmp/tt$ make
g++ -c -pipe -O2 -Wall -W -D_REENTRANT -fPIC -DPROFILE1_LIBRARY -DQT_DEPRECATED_WARNINGS -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I. -isystem /usr/include/x86_64-linux-gnu/qt5 -isystem /usr/include/x86_64-linux-gnu/qt5/QtGui -isystem /usr/include/x86_64-linux-gnu/qt5/QtCore -I. -I/usr/lib/x86_64-linux-gnu/qt5/mkspecs/linux-g++ -o profile1.o profile1.cpp
rm -f libprofile1.so.1.0.0 libprofile1.so libprofile1.so.1 libprofile1.so.1.0
g++ -Wl,-O1 -shared -Wl,-soname,libprofile1.so.1 -o libprofile1.so.1.0.0 profile1.o  /usr/lib/x86_64-linux-gnu/libQt5Gui.so /usr/lib/x86_64-linux-gnu/libQt5Core.so /usr/lib/x86_64-linux-gnu/libGL.so -lpthread    
ln -s libprofile1.so.1.0.0 libprofile1.so
ln -s libprofile1.so.1.0.0 libprofile1.so.1
ln -s libprofile1.so.1.0.0 libprofile1.so.1.0

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I'd be trying a clean rebuild:

Code:

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$ make distclean
$ qmake
$ make

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