C++/Qt: Just a LNK2019 and I don't know why - c++

Question

I have one of this unpopular LNK2019-errors in my project. Perhaps anyone can help me?
That's my header file:
#ifndef ELIST_H
#define ELIST_H
#include <QTableWidget>
class EList : public QTableWidget{
Q_OBJECT
public:
explicit EList(QWidget *parent = 0){}
~EList(){}
};
#endif // ELIST_H
and that's another cpp-file, where I want to create an object of EList in method do():
#include "elist.h"
#include "a.h"
void A::do(){
EList* el = new EList;
}
But then I get this LNK2019 error message:
a.obj:-1: Error:LNK2019: ""public: __cdecl EList::EList(class QWidget *)" (??0EList##QEAA#PEAVQWidget###Z)" in function ""public: __cdecl A::A(class QWidget *)" (??0A##QEAA#PEAVQWidget###Z)".
What did I wrong or what I have to do? I have insert all files/classes I could imagine but it did not show any effect.
EDIT: Here you can see my pro-File:
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = A
TEMPLATE = app
SOURCES += main.cpp\
a.cpp \
elist.cpp
HEADERS += a.h \
elist.h
FORMS += a.ui
RESOURCES += \
ListViewIcon.qrc
And if I change Compiler (Qt 5.1 MSVC 2012) to Microsoft (Microsoft Visual C++ Compiler 11.0), all files will compiled...

Answer 1

With C++ code, you generally can't mix-and-match compilers. Whatever C++ compiler was used to build Qt is what you should be using to build your application. You've basically answered your own question :)