仅在从命令行构建 Qt 项目时出错

Question

我有一个大问题。我创建了一个虚拟项目来隔离我的错误。因为是一个有 6 个文件的项目，无法在此处添加所有代码，所以我创建了一个 github project 并在此处添加了所有代码，同时描述了这里的想法。你可以看看那里的代码。

main.cpp的源代码：

#include <QApplication>
#include <QObject>

#include "mainwindow.h"
#include "testclass.h"

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

    MainWindow w;
    TestClass c;

    QObject::connect(&w, &MainWindow::mySignal,
                     &c, &TestClass::mySlot);

    w.show();

    return a.exec();
}

Class MainWindow 有一个 Q_SIGNAL ，当我按下 from 上的按钮时会发出， mySlot 只是 Q_SLOT in TestClass（继承 QObject）qDebug 是一条消息。

如果我从 QtCreator 构建项目，我的项目构建良好，但是当我从命令行构建它时，我收到一个奇怪的错误。

我从命令行做了什么：

$ qmake QMAKE_TEST.pro
$ make
g++ -c -m64 -pipe -O2 -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/share/qt4/mkspecs/linux-g++-64 -I. -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtGui -I/usr/include/qt4 -I. -I. -o main.o main.cpp
In file included from main.cpp:4:0:
mainwindow.h: In function ‘int main(int, char**)’:
mainwindow.h:19:7: error: ‘void MainWindow::mySignal()’ is protected
  void mySignal();
       ^
main.cpp:14:36: error: within this context
  QObject::connect(&w, &MainWindow::mySignal,
                                    ^
main.cpp:15:41: error: no matching function for call to ‘QObject::connect(MainWindow*, void (MainWindow::*)(), TestClass*, void (TestClass::*)())’
                   &c, &TestClass::mySlot);
                                         ^
main.cpp:15:41: note: candidates are:
In file included from /usr/include/qt4/QtCore/qcoreapplication.h:45:0,
                 from /usr/include/qt4/QtGui/qapplication.h:45,
                 from /usr/include/qt4/QtGui/QApplication:1,
                 from main.cpp:1:
/usr/include/qt4/QtCore/qobject.h:204:17: note: static bool QObject::connect(const QObject*, const char*, const QObject*, const char*, Qt::ConnectionType)
     static bool connect(const QObject *sender, const char *signal,
                 ^
/usr/include/qt4/QtCore/qobject.h:204:17: note:   no known conversion for argument 2 from ‘void (MainWindow::*)()’ to ‘const char*’
/usr/include/qt4/QtCore/qobject.h:217:17: note: static bool QObject::connect(const QObject*, const QMetaMethod&, const QObject*, const QMetaMethod&, Qt::ConnectionType)
     static bool connect(const QObject *sender, const QMetaMethod &signal,
                 ^
/usr/include/qt4/QtCore/qobject.h:217:17: note:   no known conversion for argument 2 from ‘void (MainWindow::*)()’ to ‘const QMetaMethod&’
/usr/include/qt4/QtCore/qobject.h:337:13: note: bool QObject::connect(const QObject*, const char*, const char*, Qt::ConnectionType) const
 inline bool QObject::connect(const QObject *asender, const char *asignal,
             ^
/usr/include/qt4/QtCore/qobject.h:337:13: note:   no known conversion for argument 2 from ‘void (MainWindow::*)()’ to ‘const char*’
make: *** [main.o] Error 1
$
$

首先为什么说 mySignal si protected 因为据我所知所有 Q_SIGNALS 都是 public？其次，如果我从运行从 Qt Creator 得到它，为什么它可以完美运行，而当我从命令行运行得到它时却出现错误？

有人可以帮我吗？

Answer 1

发现问题...我正在使用 qmake 版本 4 构建一个 Qt5.5 项目...

仅在从命令行构建 Qt 项目时出错

Error only when building Qt project from command line

c++

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qobject

qt-signals