Qt seems to leak memory everywhere - windows

Question

I have big problems with memory leaks in Qt.
The problems is that when i run methods like:
qwidget->show();
qwidget->hide();
qwidget->setVisible(...);
qlabel->setText(...);
qwidget->setEnabled(...);
then it leaks memory.
I do not create any objects on the fly. I have created all widgets on startup and I just hiding and showing widgets and changing text on some labels all the time.
And when I remove those methods, then it doesn't leaks memory at all.
Is there someone who know why it is that way or if someone knows what happens under the hood? Or does Qt have memory problems?
I run windows 7 x64 with Qt 5.0.1 x64 in release mode.
Now i have added a test code:
#include "qtmemoryleaktest.h"
#include "Content_Logs.h"
QWidget* m_placeholder;
bool m_toggle;
QtMemoryLeakTest::QtMemoryLeakTest(QWidget *parent)
: QMainWindow(parent)
{
ui.setupUi(this);
m_placeholder = new Content_Logs(this);
this->layout()->addWidget( m_placeholder );
connect( ui.pushButton, &QPushButton::clicked, this, &QtMemoryLeakTest::toggleClick );
}
void QtMemoryLeakTest::toggleClick()
{
if( m_toggle = !m_toggle )
{
m_placeholder->show();
}
else
{
m_placeholder->hide();
}
}
Memory grows everytime a click on the button. from 8 mb to 47 mb in 20 minutes. But if a replace Content_Logs to a QWidget, no memory leaks. So i Think there is a bug in Qts self gererated ui-classes? In Content_Logs i have labels, lineEdits, Spacers, TableWidgets, Checkboxes, DateTimeEdits, ComboBoxes and so on.
Code in Conte_Logs:
#include "Content_Logs.h"
Content_Logs::Content_Logs( QWidget* parent = 0 )
: QWidget( parent )
{
ui.setupUi( this );
}
Content_Logs::~Content_Logs()
{
}