Question

moc_mm.o: In function `Counter::metaObject() const':
moc_mm.cpp:(.text+0x0): multiple definition of `Counter::metaObject() const'
moc_joystick.o:moc_joystick.cpp:(.text+0x0): first defined here
moc_mm.o:(.rodata+0x0): multiple definition of `Counter::staticMetaObject'

我应该在这里介绍哪部分代码，w.r.t这个错误？
这个错误是什么意思？

我已经 make clean ，但这没有帮助。函数名称 metaObject 似乎是Qt的内部。

编辑1：
添加头文件：

#include <stdio.h>
#include <QObject>
#ifndef __JOYSTICK_H__
#define __JOYSTICK_H__

#define JOYSTICK_DEVNAME "/dev/input/js0"

#define JS_EVENT_BUTTON         0x01    /* button pressed/released */
#define JS_EVENT_AXIS           0x02    /* joystick moved */
#define JS_EVENT_INIT           0x80    /* initial state of device */


struct js_event {
    unsigned int time;  /* event timestamp in milliseconds */
    short value;   /* value */
    unsigned char type;     /* event type */
    unsigned char number;   /* axis/button number */
};

struct wwvi_js_event {
    int button[11];
    int stick_x;
    int stick_y;
};

class Counter : public QObject
 {
    Q_OBJECT
    private:
        int m_value;

    public:
        Counter() { m_value = 0; }

        int value() const { return m_value; }

    //public slots:
        int open_joystick();
        int read_joystick_event(struct js_event *jse);
        //void set_joystick_y_axis(int axis);
        //void set_joystick_x_axis(int axis);
        void close_joystick();
        int get_joystick_status(struct wwvi_js_event *wjse);

    //signals:
        //void valueChanged(int newValue);
 };
#endif

输出：

anisha@linux-dopx:~/Desktop/anishaJoystick> qmake -project
anisha@linux-dopx:~/Desktop/anishaJoystick> qmake
anisha@linux-dopx:~/Desktop/anishaJoystick> make
g++ -m64 -Wl,-O1 -Wl,-rpath,/home/anisha/qtsdk-2010.05/qt/lib -o anishaJoystick joy.o mm.o moc_joystick.o moc_mm.o    -L/home/anisha/qtsdk-2010.05/qt/lib -lQtGui -L/home/anisha/qtsdk-2010.05/qt/lib -L/usr/X11R6/lib64 -lQtCore -lpthread 
moc_mm.o: In function `Counter::metaObject() const':
moc_mm.cpp:(.text+0x0): multiple definition of `Counter::metaObject() const'
moc_joystick.o:moc_joystick.cpp:(.text+0x0): first defined here
moc_mm.o:(.rodata+0x0): multiple definition of `Counter::staticMetaObject'
moc_joystick.o:(.rodata+0x0): first defined here
moc_mm.o: In function `Counter::qt_metacast(char const*)':
moc_mm.cpp:(.text+0x20): multiple definition of `Counter::qt_metacast(char const*)'
moc_joystick.o:moc_joystick.cpp:(.text+0x30): first defined here
moc_mm.o: In function `Counter::valueChanged(int)':
moc_mm.cpp:(.text+0x70): multiple definition of `Counter::valueChanged(int)'
mm.o:mm.cpp:(.text+0x10): first defined here
moc_mm.o: In function `Counter::qt_metacall(QMetaObject::Call, int, void**)':
moc_mm.cpp:(.text+0xb0): multiple definition of `Counter::qt_metacall(QMetaObject::Call, int, void**)'
moc_joystick.o:moc_joystick.cpp:(.text+0x20): first defined here
collect2: ld returned 1 exit status
make: *** [anishaJoystick] Error 1

源文件：

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

#include "joystick.h"

static int joystick_fd = -1;

int Counter::open_joystick()
{
    joystick_fd = open(JOYSTICK_DEVNAME, O_RDONLY | O_NONBLOCK); // read write for force feedback?
    if (joystick_fd < 0)
        return joystick_fd;

    // maybe ioctls to interrogate features here? 

    return joystick_fd;
}

int Counter::read_joystick_event(struct js_event *jse)
{
    int bytes;

    bytes = read(joystick_fd, jse, sizeof(*jse)); 

    if (bytes == -1)
        return 0;

    if (bytes == sizeof(*jse))
        return 1;

    printf("Unexpected bytes from joystick:%d\n", bytes);

    return -1;
}

void Counter:: close_joystick()
{
    close(joystick_fd);
}

int Counter::get_joystick_status(struct wwvi_js_event *wjse)
{
    int rc;
    struct js_event jse;
    if (joystick_fd < 0)
        return -1;

    // memset(wjse, 0, sizeof(*wjse));
    while ((rc = read_joystick_event(&jse) == 1)) {
        jse.type &= ~JS_EVENT_INIT; /* ignore synthetic events */
        if (jse.type == JS_EVENT_AXIS) {
            switch (jse.number) {
            case 0: wjse->stick_x = jse.value;
                break;
            case 1: wjse->stick_y = jse.value;
                break;
            default:
                break;
            }
        } else if (jse.type == JS_EVENT_BUTTON) {
            if (jse.number < 10) {
                switch (jse.value) {
                case 0:
                case 1: wjse->button[jse.number] = jse.value;
                    break;
                default:
                    break;
                }
            }
        }
    }
    // printf("%d\n", wjse->stick1_y);
    return 0;
}

//#if 0
/* a little test program */
int main(int argc, char *argv[])
{
    int fd, rc;
    int done = 0;

    struct js_event jse;

    Counter c;
    fd = c.open_joystick();
    if (fd < 0) {
        printf("open failed.\n");
        exit(1);
    }

    while (!done) {
        rc = c.read_joystick_event(&jse);
        usleep(1000);
        if (rc == 1) {
            printf("Event: time %8u, value %8hd, type: %3u, axis/button: %u\n", jse.time, jse.value, jse.type, jse.number);
        }
    }
}
//#endif

Answer 1

您的目录中可能有多个moc_ *文件（可能是一些重命名后的旧文件），并且运行qmake -project已在您的构建中包含旧文件。它找到了相同名称（moc_mm.cpp和moc_joystick.cpp）的多个moc_ *声明和冲突。

手动删除所有moc_ *文件，并使用-project重新创建.pro文件。

Answer 2

当您不小心两次将Q_OBJECT宏用于同一个类时，也会发生此错误。

例如，我只是在从.cpp文件（如here所述，在声明和实现的源代码布局到将它们分成{ {1}}和.h。映射到您的示例代码，我的代码如下：

.cpp：与问题完全相同，包括此关键部分以及宏调用：
```
joystick.h
```
class Counter : public QObject { Q_OBJECT // ... method declarations here ... };，包括原始实现遗留的意外第二个宏调用，完全在此处：
```
joystick.cpp
```

Answer 3

如果您有2个头文件，或者您的.h文件中缺少包含病房，则也会出现此错误

您可能不小心复制了一个头文件，并且在刷新项目之前可能看不到它。

要刷新您的项目，请在.pro中添加空格，然后保存并运行qmake。

`Counter :: metaObject（）const'的多重定义

3 个答案: