代码如下：
QPushButton *btn = new QPushButton(this);
btn->setText(tr("button"));
ui->horizontalLayout->addWidget(btn);
connect(btn,SIGNAL(clicked()),this,SLOT(mySlot()));
void MainWindow::mySlot()
{
QPushButton *button = qobject_cast<QPushButton*>(sender());
if (button == NULL) return;
qDebug()<<button->text();
}
执行到QPushButton *button = qobject_cast<QPushButton*>(sender());这一行时，程序崩溃了。提示如下：
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
can't find linker symbol for virtual table for `QPushButton' value
found `QMainWindow::staticMetaObjectExtraData' instead
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
(Internal error: pc 0x201 in read in psymtab, but not in symtab.)
求高手指点，问题出在哪里
