cannot convert from pointer to base class 'QObject' to pointer to derived class 'subClass' via virtual base 'baseClass'

QT 编译不过的另一个问题：

1. 新建一个console工程

QT -= gui

CONFIG += c++ console
CONFIG -= app_bundle

# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.

SOURCES += \
        main.cpp \
    baseclass.cpp \
    subclass.cpp \
    subclass2.cpp
    #grandclass.cpp

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

HEADERS += \
    baseclass.h \
    subclass.h \
    subclass2.h
    #grandclass.h

2. 添加baseClass

baseclass.h

#ifndef BASECLASS_H
#define BASECLASS_H

#include "QObject"

class baseClass: public QObject
{
    Q_OBJECT

public:
    baseClass(QObject * p = );
    virtual ~baseClass() {}

    virtual void vMethod(int) = ;

signals:
    void signal1();

};

#endif // BASECLASS_H

baseclass.cpp

#include "baseclass.h"

baseClass::baseClass(QObject * p) : QObject(p)
{

}

3. 添加subClass

subclass.h

#ifndef SUBCLASS_H
#define SUBCLASS_H

#include "baseclass.h"

class subClass: virtual public baseClass
{
    Q_OBJECT

public:
    subClass(QObject * p = );
    virtual ~subClass() {};
    virtual void vMethod(int) = ;

signals:
    void signal2();

};

#endif // SUBCLASS_H

subclass.cpp

#include "subclass.h"

subClass::subClass(QObject * p) : baseClass (p)
{

}

4. 添加subClass2

subclass2.h

#ifndef SUBCLASS2_H
#define SUBCLASS2_H

#include "baseclass.h"

class subClass2 : virtual public baseClass
{
    Q_OBJECT

public:
    subClass2(QObject * p = 0);

    virtual void vMethod(int) = ;

};

#endif // SUBCLASS2_H

subclass2.cpp

#include "subclass2.h"

subClass2::subClass2(QObject * p) : baseClass (p)
{

}

5 main.cpp

#include <QCoreApplication>
#include "subclass.h"
//#include "grandclass.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    //grandClass * sub = new grandClass();

    return a.exec();
}

编译报错：/build-testQtSignalBug-Qt5_9_4_zynq-Debug/moc_subclass.cpp:68: error: cannot convert from pointer to base class 'QObject' to pointer to derived class 'subClass' via virtual base 'baseClass'

subClass *_t = static_cast<subClass *>(_o);
^

解决方法： 将subclass里的signals 删掉， 即不在subclass里声明信号量。

原因：不详。