Pre-incrementation -> strange thing

feniks_fire

Hey,
I have this code

#include <QCoreApplication>
#include <QDebug>
int main(int argc, char *argv[])
{
	QCoreApplication a(argc, argv);
	int b = 1;
	int c = ++b + ++b;
	qDebug()<<c;
	b = 1;
	c = ++b + ++b + ++b;
	qDebug()<<c;
	b = 1;
	c = ++b + ++b + ++b + ++b;
	qDebug()<<c;
	b = 1;
	c = ++b + ++b;
	c += ++b + ++b;
	qDebug()<<c;
	return a.exec();
}

and I get this value

I cannot imagine why is such and no other result.
Someone can explain me?

SGaist

Hi,

Take a look at the here and its associated note about order of evaluation.

AFAIK, you're in the undefined behaviour territory.

feniks_fire

Thanks, for reply.
I don't expect that this can be UB, even in my dreams :|.

Anyway topic solved.