Heap corruption when Enumerating QActions in a QMenu in 6.8.1

bfjtg

I am moving an application from Qt5 in VS2019 to Qt6 in VS2022. All the code compiled with no changes. However, when I run the code, after the loop below finishes, I get a heap corruption error.

Ui::imageDisplayWindow m_ui;
QMenu *menuColor_Palette; // holds 7 menu items

for (auto *const palette : m_ui.menuColor_Palette->actions())
{
    const bool isSender = palette == sender;
    palette->setChecked(isSender);
    if (isSender)
        m_colorPaletteButton->setText("Palette: " + palette->text());
}

The code breaks here during clean up exiting the loop context.

~QArrayDataPointer()
{
    if (!deref()) {
        (*this)->destroyAll();
        free(d);
    }
} <--break point

Not helpful, but here's the error message.

The Actions are just menu items:

QAction *actionColor_Palette_Gray
QAction *actionColor_Palette_Gray_2x
....

m_colorPaletteMenu->addAction(m_ui.actionColor_Palette_Gray);
m_colorPaletteMenu->addAction(m_ui.actionColor_Palette_Gray_2x);
....

Note that if I comment the code inside the loop out, i.e. do nothing, I still get the heap error:

for (auto *const palette : m_ui.menuColor_Palette->actions())
{
}

I have the same problem with the ~10 for() loops that iterate a QList<QAction*> list.

This code works correctly Qt 5.15.2 in VS2019

If I convert this loop to "C" style it works correctly

QList<QAction*> const ActionList = m_ui.menuColor_Palette->actions();
QAction* palette;
int i;

for (i = 0; i < ActionList.size(); i++)
{
    palette = ActionList[i];
    const bool isSender = palette == sender;
    palette->setChecked(isSender);
    if (isSender)
        m_colorPaletteButton->setText("Palette: " + palette->text());
}

Any thoughts on what is going wrong here?

It seems odd that such a straight forward for() operation would change between Qt5 and Qt6. But I am wondering if I am doing something wrong upstream. The code making the action list is pretty simple. Any help is appreciated.

SGaist

Hi and welcome to devnet,

One difference is the implementation of QList that changed but I don't think it's the issue at hand.

What if you use just auto * without const ?

Christian Ehrlicher

Don't mix debug and release libraries.

hskoglund

Maybe you got bitten by the ranged-based for loop over temp. values bug,,,

bfjtg

Wow, thank you for all the quick responses. I will check these all out and report back ASAP.

bfjtg

Christian's suggestion solved the problem. I had a mix of release and debug libraries. Made them all debug and the problem disappeared.

For the record, I did try dropping the const, but that did not help.

The "ranged-based loop over temp values" is scary and I was very much hoping that I would not need to go there.

Thanks everyone for your help, very much appreciated.