Qt未定义对vtable的引用 [英] Qt undefined reference to vtable
问题描述
我是一个初学者Qt编程和使用代码块我的编程。我创建了3个文件communications.h,commmunicate.cpp和main.cpp如下:
communic.h
#ifndef COMMUNICATE_H
#define COMMUNICATE_H
#include< QWidget>
#include< QApplication>
#include< QPushButton>
#include< QLabel>
class Communicate:public QWidget
{
Q_OBJECT
public:
Communicate(QWidget * parent = 0);
私有插槽:
void OnPlus();
void OnMinus();
private:
QLabel * label;
};
#endif
communicate.cpp / p>
#includecommunic.h
Communicate :: Communicate(QWidget * parent)
:QWidget(parent)
{
QPushButton * plus = new QPushButton(+,this);
plus-> setGeometry(50,40,75,30);
QPushButton * minus = new QPushButton( - ,this);
minus-> setGeometry(50,100,75,30);
label = new QLabel(0,this);
label-> setGeometry(190,80,20,30);
connect(plus,SIGNAL(clicked()),this,SLOT(OnPlus()));
connect(minus,SIGNAL(clicked()),this,SLOT(OnMinus()));
}
void Communicate :: OnPlus()
{
int val = label-> text()。
val ++;
label-> setText(QString :: number(val));
}
void Communicate :: OnMinus()
{
int val = label-> text()。
val--;
label-> setText(QString :: number(val));
}
main.cpp
$ b
#includecommunic.h
int main(int argc,char * argv [])
{
QApplication app(argc,argv);
通信窗口;
window.setWindowTitle(Communicate);
window.show();
return app.exec();
}
及其显示错误如下:
obj \Debug\main.o(.text $ _ZN11CommunicateD1Ev [Communicate ::〜Communicate()] + 0xb)||函数`ZN7QStringC1EPKc':|
C:\Qt\4.4.3\include\QtCore\..\..\src\corelib\arch\qatomic_windows.h ||未定义的引用`vtable for沟通
obj\Debug\main.o(.text $ _ZN11CommunicateD1Ev [Communicate ::〜Communicate()] + 0x17):C:\Qt\4.4.3\include\QtCore\。 .\..\src\corelib\arch\qatomic_windows.h ||未定义的引用`vtable for Communicate'|
obj\Debug\communicate.o(.text + 0x172)||在函数`ZN11CommunicateC2EP7QWidget':|
E:\Project\cam2\communicate.cpp | 5 |未定义引用`vtable for Communicate'|
obj\Debug\communicate.o(.text + 0x17e):E:\Project\cam2\communicate.cpp | 5 |未定义引用`vtable for Communicate'|
obj\Debug\communicate.o(.text + 0x63a)||在函数`ZN11CommunicateC1EP7QWidget':|
E:\Project\cam2\communicate.cpp | 5 |未定义引用`vtable for Communicate'|
obj\Debug\communicate.o(.text + 0x646):E:\Project\cam2\communicate.cpp | 5 |更多未定义的引用`vtable for Communicate'跟随|
|| === Build finished:6 errors,0 warnings === |
家伙请帮忙...难以置信...
这是我以前见过的一个微妙的错误(可能部分至少是一个编译器错误)。由于QWidget有一个虚拟析构函数,编译器需要一个vtable为你的类。但是你的类没有任何虚拟函数,所以它没有为你的Communicate类构建一个。
向您的班级添加 virtual〜Communicate(){};
p>
是的,我花了一些时间来弄清楚这一点!
I am a beginner to Qt programming and use codeblocks for my programming. I created 3 files communicate.h,commmunicate.cpp and main.cpp as follows:
communicate.h
#ifndef COMMUNICATE_H
#define COMMUNICATE_H
#include <QWidget>
#include <QApplication>
#include <QPushButton>
#include <QLabel>
class Communicate : public QWidget
{
Q_OBJECT
public:
Communicate(QWidget *parent = 0);
private slots:
void OnPlus();
void OnMinus();
private:
QLabel *label;
};
#endif
communicate.cpp
#include "communicate.h"
Communicate::Communicate(QWidget *parent)
: QWidget(parent)
{
QPushButton *plus = new QPushButton("+", this);
plus->setGeometry(50, 40, 75, 30);
QPushButton *minus = new QPushButton("-", this);
minus->setGeometry(50, 100, 75, 30);
label = new QLabel("0", this);
label->setGeometry(190, 80, 20, 30);
connect(plus, SIGNAL(clicked()), this, SLOT(OnPlus()));
connect(minus, SIGNAL(clicked()), this, SLOT(OnMinus()));
}
void Communicate::OnPlus()
{
int val = label->text().toInt();
val++;
label->setText(QString::number(val));
}
void Communicate::OnMinus()
{
int val = label->text().toInt();
val--;
label->setText(QString::number(val));
}
main.cpp
#include "communicate.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
Communicate window;
window.setWindowTitle("Communicate");
window.show();
return app.exec();
}
and its showing errors as follows:
obj\Debug\main.o(.text$_ZN11CommunicateD1Ev[Communicate::~Communicate()]+0xb)||In function `ZN7QStringC1EPKc':|
C:\Qt\4.4.3\include\QtCore\..\..\src\corelib\arch\qatomic_windows.h||undefined reference to `vtable for Communicate'|
obj\Debug\main.o(.text$_ZN11CommunicateD1Ev[Communicate::~Communicate()]+0x17):C:\Qt\4.4.3\include\QtCore\..\..\src\corelib\arch\qatomic_windows.h||undefined reference to `vtable for Communicate'|
obj\Debug\communicate.o(.text+0x172)||In function `ZN11CommunicateC2EP7QWidget':|
E:\Project\cam2\communicate.cpp|5|undefined reference to `vtable for Communicate'|
obj\Debug\communicate.o(.text+0x17e):E:\Project\cam2\communicate.cpp|5|undefined reference to `vtable for Communicate'|
obj\Debug\communicate.o(.text+0x63a)||In function `ZN11CommunicateC1EP7QWidget':|
E:\Project\cam2\communicate.cpp|5|undefined reference to `vtable for Communicate'|
obj\Debug\communicate.o(.text+0x646):E:\Project\cam2\communicate.cpp|5|more undefined references to `vtable for Communicate' follow|
||=== Build finished: 6 errors, 0 warnings ===|
guys please help...cant figure it out...
This is a subtle bug (and probably partly at least a compiler bug) that I've seen before. Since QWidget has a virtual destructor, the compiler needs a vtable for your class. But your class doesn't have any virtual functions, so it didn't build one for your Communicate class.
Add a virtual ~Communicate() {};
to your class, and all will be well.
Yes, it took me some time to figure this out too!
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