Link errors for plugin under windows

I am using Qt4.5 technology preview with VS2008 and I am having problem building a test plugin:

1>pltest.obj : error LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall MyClearing::metaObject(void)const " (?metaObject@MyClearing@@UBEPBUQMetaObject@@XZ)
1>pltest.obj : error LNK2001: unresolved external symbol "public: virtual void * __thiscall MyClearing::qt_metacast(char const *)" (?qt_metacast@MyClearing@@UAEPAXPBD@Z)
1>pltest.obj : error LNK2001: unresolved external symbol "public: virtual int __thiscall MyClearing::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@MyClearing@@UAEHW4Call@QMetaObject@@ HPAPAX@Z)

This plugin has following code:

test.h file
class Clearing
{
public:
virtual ~Clearing(){};
virtual int Count () = 0;
};

Q_DECLARE_INTERFACE(Clearing,
"TestPlugin.1");

pltest.cpp file
#include <QObject>
#include <QtPlugin>
#include "test.h"

class MyClearing : public QObject, public Clearing
{
Q_OBJECT
Q_INTERFACES(Clearing)
public:
int Count () {return 1;}
};Q_EXPORT_PLUGIN2(PLTest, MyClearing)

Linker options:
/OUT:"<pathtoproject>\PLTest.dll" /NOLOGO /LIBPATH:"<pathtoQT45\lib" /DLL /MANIFEST /MANIFESTFILE:"Debug\PLTest.dll.intermediate.manife st" /MANIFESTUAC:"level='asInvoker' uiAccess='false'" /DEBUG /PDB:"<pathtoproject>\Debug\PLTest.pdb" /SUBSYSTEM:WINDOWS /DYNAMICBASE /NXCOMPAT /ERRORREPORT:PROMPT qtmaind.lib QtGuid4.lib QtCored4.lib kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib

You have to moc your MyClearing class with the Qt tool "moc". If you have
a qt project file (.pro) you can:

1) Run qmake && nmake for building through console
or
2) Run qmake -t vcapp for building in MSVS2008

Well, I don't know if that is the problem. The reason I think that it might be something else is an output from the compiler when I build the project. MyClearing class implementation is in pltest.cpp, so it looks like it is "moc"-ed. And pltest.moc is generated and placed in GeneratedFiles\Debug directory


Deleting intermediate and output files for project 'PLTest', configuration 'Debug|Win32'
1>Moc'ing pltest.cpp...
1>Compiling...
1>pltest.cpp
1>Linking...
1> Creating library <pathtoproject>\Debug\PLTest.lib and object <pathtoproject>\Debug\PLTest.exp
1>pltest.obj : error LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall MyClearing::metaObject(void)const " (?metaObject@MyClearing@@UBEPBUQMetaObject@@XZ)
1>pltest.obj : error LNK2001: unresolved external symbol "public: virtual void * __thiscall MyClearing::qt_metacast(char const *)" (?qt_metacast@MyClearing@@UAEPAXPBD@Z)
1>pltest.obj : error LNK2001: unresolved external symbol "public: virtual int __thiscall MyClearing::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@MyClearing@@UAEHW4Call@QMetaObject@@ HPAPAX@Z)
1><pathtoproject>\PLTest.dll : fatal error LNK1120: 3 unresolved externals

Did you include pltest.moc in pltest.cpp? It should be like this:

Code:

---

//pltest.cpp file
#include <QObject>
#include <QtPlugin>
#include "test.h"
 
class MyClearing : public QObject, public Clearing
{
Q_OBJECT
Q_INTERFACES(Clearing)
public:
int Count () {return 1;}
};Q_EXPORT_PLUGIN2(PLTest, MyClearing)
 
 
#include "pltest.moc"

---

Thank you so much! That was it. I wonder, though, is it mentioned anywhere in Qt docs? I mean, that "<file>.moc has to be included directly? I personally did not find it anywhere in the docs...

You're welcome!

Please see http://doc.trolltech.com/4.4/moc.html

Writing Make Rules for Invoking moc

Quote:

---

....
For Q_OBJECT class declarations in implementation (.cpp) files, we suggest a makefile rule like this:

foo.o: foo.moc

foo.moc: foo.cpp
moc $(DEFINES) $(INCPATH) -i $< -o $@

This guarantees that make will run the moc before it compiles foo.cpp. You can then put

#include "foo.moc"

at the end of foo.cpp, where all the classes declared in that file are fully known.

---