Why A non-void setter function in a property results in CTD (Segmentation fault) in 'Release' build mode only?

Curtwagner1984

Hello, I've ran into a curious phenomena that I don't understand. I made a property for my class and when implementing the setter, I copied the getter with it's return type and forgot to fix it. The getter had a bool return type.

Everything work fine in DEBUG mode but when I complied in RELEASE every time I set the property value, the program would crush with a SEGFAULT without any meaningful way to debug the error or a helpful error message.

After more time than I care to admit I found that I forgot to fix the return type, and I fixed it. The crushes stopped.

What I want to know is why. Why did it work in DEBUG but crushed in RELEASE and why a setter having void as a return type in a property is a must?

Here is an example:

Consider this class:

class StubClass : public QObject
{
  Q_OBJECT
  
  StubClass(){
    _isTrue = false;
  }

public:
    Q_PROPERTY(bool isTrue READ isTrueGetter WRITE isTrueSetter NOTIFY isTrueChanged);

    bool isTrueGetter(){
        return this->_isTrue;
    }

    void isTrueSetter(bool newIsTrue){
        this->isTrue = newIsTrue;
        emit this->isTrueChanged();
    }

signals:
    void isTrueChanged();

private: 
    bool _isTrue;
}

Like this it works in both release and debug but if I change:

    void isTrueSetter(bool newIsTrue){
        this->isTrue = newIsTrue;
        emit this->isTrueChanged();
    }

To:

    bool isTrueSetter(bool newIsTrue){
        this->isTrue = newIsTrue;
        emit this->isTrueChanged();
    }

It crushes in Release only.

Christian Ehrlicher

Simplify your program until it no longer crashes.
Also you can compile your program in release with debug information to get a useful backtrace. You code above can not crash but you don't show us how you call this call. I would guess it a dangling pointer.

Curtwagner1984

Also you can compile your program in release with debug information to get a useful backtrace.

How do you do that?

Christian Ehrlicher

@Curtwagner1984 said in Why A non-void setter function in a property results in CTD (Segmentation fault) in 'Release' build mode only?:

How do you do that?

What build system do you use?

SGaist

@Curtwagner1984 said in Why A non-void setter function in a property results in CTD (Segmentation fault) in 'Release' build mode only?:

Like this it works in both release and debug but if I change:

    void isTrueSetter(bool newIsTrue){
        this->isTrue = newIsTrue;
        emit this->isTrueChanged();
    }

To:

    bool isTrueSetter(bool newIsTrue){
        this->isTrue = newIsTrue;
        emit this->isTrueChanged();
    }

It crushes in Release only.

Hi,

You do not return anything in the latter hence it's undefined behaviour.
You likely have a warning about it when compiling, don't leave warning in your code.