Plugin system - DLLs and unresolved external symbols

Peppy

Hi guys, I have one (big) issue creating plug-n-play system of plugins, which my app deserves...the issue is that application is missing
external symbols, I was following step-by-step Plug-n-paint example, but I have discovered, it's a static linking. I want to create plugins via dynamic linking, is it possible, or not?

lgeyer

Of course. Plugins are dynamically linked by default.

Please post your .pro files as well the linker error.

Peppy

Here is it: App.pro:
@
QT += core gui network

TARGET = App
TEMPLATE = app

SOURCES += main.cpp
SingleApplication.cpp

HEADERS +=
SingleApplication.h
@

Linker says that:
@
core.obj:-1: error: LNK2001: unresolved external symbol "public: static struct QMetaObject const Core::staticMetaObject" (?staticMetaObject@Core@@2UQMetaObject@@B)
core.obj:-1: error: LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall Core::metaObject(void)const " (?metaObject@Core@@UBEPBUQMetaObject@@XZ)
core.obj:-1: error: LNK2001: unresolved external symbol "public: virtual void * __thiscall Core::qt_metacast(char const *)" (?qt_metacast@Core@@UAEPAXPBD@Z)
core.obj:-1: error: LNK2001: unresolved external symbol "public: virtual int __thiscall Core::qt_metacall(enum QMetaObject::Call,int,void * *)"
core.obj:-1: error: LNK2001: unresolved external symbol "public: virtual void __thiscall interface::hello(void)" (?hello@interface@@UAEXXZ)(?qt_metacall@Core@@UAEHW4Call@QMetaObject@@HPAPAX@Z)
........\App\bin\debug\App.Core.dll:-1: error: LNK1120: 5 unresolved externals
@

And library project file:
@
TARGET = App.Core
TEMPLATE = lib

CONFIG += plugin

DEFINES += CORE_LIBRARY

SOURCES += core.cpp

HEADERS += core.h
Core_global.h
interface.h

symbian {
MMP_RULES += EXPORTUNFROZEN
TARGET.UID3 = 0xE2EB6093
TARGET.CAPABILITY =
TARGET.EPOCALLOWDLLDATA = 1
addFiles.sources = Core.dll
addFiles.path = !:/sys/bin
DEPLOYMENT += addFiles
}

unix:!symbian {
maemo5 {
target.path = /opt/usr/lib
} else {
target.path = /usr/lib
}
INSTALLS += target
}

@

Peppy

hey guys, c'mon! :)...

Sam

Hi,

Dont know whether this will help or not, but you can have a look in this "tutorial":http://www.voidrealms.com/viewtutorial.aspx?id=246 that explains about how to create and load plugins.

chernetsov0

Without
@CONFIG += plugin@

you need to write such a structure before the class (or place it into header and include it if you export more than one class)

@#ifndef CORE_LIBRARY
#define APP_CORE_EXPORTS Q_DECL_IMPORT
#else
#define APP_CORE_EXPORTS Q_DECL_EXPORT
#endif@

and declare classes like this
@
class APP_CORE_EXPORTS AppCore@

[quote author="Peppy" date="1346020550"] I want to create plugins via dynamic linking, is it possible, or not?[/quote]

Qt plugins are dynamically loaded from their .dll/.so files by QPluginLoader so it is actually not only possible but is the case unless you use Q_IMPORT_PLUGIN.

Hope this helps!