Abstract plugin inheritance error

SGaist

Hi,

The usual setup when building a plugin based application is to have the plugin interfaces definitions and related code in a library that you will link to both the plugin and the application.

That's what is suggested here.

Defohin

@SGaist I'm really struggling to understand, can you provide an example, please?

SGaist

Roughly :
pluginfoo.pro

QT          += core gui
TARGET       = pluginfoo
TEMPLATE     = lib
CONFIG      += plugin
DESTDIR      = $$OUTPWD/bin/plugins
LIBS += -L$$OUTPWD/lib -lmycoollib
DEFINES     += QT_DEPRECATED_WARNINGS
INCLUDEPATH += ../mycoollib
SOURCES     += pluginfoo.cpp
HEADERS     += pluginfoo.hpp
DISTFILES   += pluginfoo.json

mycoollib.pro

QT          += core gui
TARGET       = mycoollib
TEMPLATE  = lib
DESTDIR      = $$OUTPWD/lib
INCLUDEPATH += .
SOURCES     += \
    abstractplugin.cpp
HEADERS     += \
    plugininterface.hpp
    abstractplugin.hpp

myproject.pro

QT      += core gui widgets xml network
TARGET   = myproject
TEMPLATE = app
DESTDIR  = $$OUTPWD/bin
LIBS += -L$$OUTPWD/lib -lmycoollib
INCLUDEPATH += ../mycoollib
DEFINES += QT_DEPRECATED_WARNINGS
SOURCES += src/main.cpp \
           gui/myprojectwindow.cpp

HEADERS += gui/myprojectwindow.hpp

Project structure

mycoolproject \
---- mycoollib
---- pluginfoo
---- myproject

mycoolproject being a SUBDIR project building first mycoollib and then pluginfoo and myproject.

Defohin

@SGaist Do I have to link with -l every single plugin I have? Or I can just provide a path like -L and it's going to work?

I will try to modify here based on your example.

SGaist

You don't link the plugins. You link your plugins against that common library.

Yes, you have to use both -land -L.

-L just tells the linker where to look at.

Defohin

@SGaist It works, but I have another question now.

I named the "commonlib" to "pluginmanager" this class will hold information about plugins, load, unload and so on using QPluginLoader, but... when I try to use it on the main application including the header pluginmanager.hpp it says that it cannot open the file, even if I have the INCLUDEPATH += ../pluginmanager. On Qt Creator it does work, I'm able to ctrl+click, etc, but when I try to compile I get this error.

jsulm

@Defohin Did you run qmake again after changing the pro file? After qmake you should do a complete rebuild.

Defohin

@jsulm It works, but now I'm getting unresolved external symbol on the main project when trying to use PluginManager manager on the MyProjectWindow, and I have LIBS += -L../libs -lpluginmanager on the pro file.

myprojectwindow.obj:-1: error: LNK2019: unresolved external symbol "public: __cdecl PluginManager::PluginManager(class QObject *)" (??0PluginManager@@QEAA@PEAVQObject@@@Z) referenced in function "public: __cdecl MyProjectWindow::MyProjectWindow(class QWidget *)" (??0MyProjectWindow@@QEAA@PEAVQWidget@@@Z)

jsulm

@Defohin ../libs is a relative path, are you sure it is correct?
Can you post the compiler/linker call just before the error message?
As suggested by @SGaist : LIBS += -L$$OUTPWD/lib -lmycoollib (pluginmanager instead of mycoollib)

Defohin

@jsulm I'm using $$OUTPWD now but it still doesn't work.

jsulm

@Defohin Is the resulting path correct and is the lib there?

Defohin

It's working now, I forgot to put MYPROJECT_EXPORT on PluginManager class.

I love you guys ♥