undefined reference to `vtable for class::method'－－链接共享库时出现

最近用Qt写一个项目时出现了undefined reference to 'vtable for class::methode'的错误！

一 描述

程序结构如下：

共享库： libyqmath.so 有个类CMyDraw －－完成一些绘画操作

1. 编译成功，存放在../../../lib/中，即../../../lib/中有libyqmath.so libyqmath.so.1 ...

GUI应用程序：demo

1. 调用CMyDraw进行绘画

2. 在.pro文件中加入了: LIBS += -L../../../li/libyqmath.so

INCLUDEPATH += . ./../../../include ./../../../lib

make时出现如下错误信息：

g++ -Wl,-O1 -o ../../../bin/demo build/cmydrawdlg.o build/cmymathdlg.o build/main.o build/moc_cmydrawdlg.o build/moc_cmymathdlg.o -L/usr/lib -L../../../bin/libyqmath.so -lQtGui -lQtCore -lpthread

build/cmydrawdlg.o: In function `CMyDrawDlg::CMyDrawDlg()':

/home/yangjingtu/projects/study/qt/code/demo/src/cmydrawdlg.cpp:35: undefined reference to `CMyDraw::CMyDraw()'

build/cmydrawdlg.o: In function `~CMyDraw':

/home/yangjingtu/projects/study/qt/code/demo/src/../../yqmath/src/cmydraw.h:36: undefined reference to `vtable for CMyDraw

/home/yangjingtu/projects/study/qt/code/demo/src/../../yqmath/src/cmydraw.h:36: undefined reference to `vtable for CMyDraw

build/cmydrawdlg.o: In function `CMyDrawDlg::MyDraw()':

/home/yangjingtu/projects/study/qt/code/demo/src/cmydrawdlg.cpp:70: undefined reference to `CMyDraw::DrawMyRect(QPicture*, int, int, int, int)'

build/main.o: In function `~CMyDraw':

/home/yangjingtu/projects/study/qt/code/demo/src/../../yqmath/src/cmydraw.h:36: undefined reference to `vtable for CMyDraw

/home/yangjingtu/projects/study/qt/code/demo/src/../../yqmath/src/cmydraw.h:36: undefined reference to `vtable for CMyDraw'

/home/yangjingtu/projects/study/qt/code/demo/src/../../yqmath/src/cmydraw.h:36: undefined reference to `vtable for CMyDraw'

/home/yangjingtu/projects/study/qt/code/demo/src/../../yqmath/src/cmydraw.h:36: undefined reference to `vtable for CMyDraw'

build/cmymathdlg.o: In function `CMyMathDlg::intadd()':

/home/yangjingtu/projects/study/qt/code/demo/src/cmymathdlg.cpp:54: undefined reference to `MyMathInt::add(int, int)'

collect2: 错误：ld 返回 1

二 原因

百度，google了一大圈基本分为两大类：

1. 用了Q_OBJECT的宏，但没有包含其moc文件或没有加到链接列表中去。

2. 所依赖的库文件问题。

排除1，因为共享库已生成成功，那原因就是库或其路径问题。

三 解决方案

尝试1： 更改.pro文件

LIBS += -lyqmath

qmake make后出现： /usr/bin/ld: cannot find -lyqmath

改回

LIBS += -L../../../lin/libyqmath.so

不会出现cannot find问题，那说明路径是对的，程序也找到相应该的库

尝试2： 在/etc/ld.so.conf.d/下添加my-project.conf文件并把路径加进去

sudo vim /ect/ld.so.conf.d/my-project.conf

> .../project/study/qt/lib

sudo ldcofig

再尝试1的方法，问题依旧

尝试3： 更改.pro文件

LIBS += -L../../../lib -lyqmath

qmake make后：太帅了成功了！

一定要注意LIBS的写法！！！！

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