Deleting an object?

[CroCo]

I'm accessing a memeber function of an object that has been deleted. My question is why the compiler didn't complain? I'm using Qt.

#include <QDebug>
#include "myclass.h"

int main(int argc, char *argv[])
{
    QObject parent;
    MyClass *a, *b, *c;

    a = new MyClass("foo", &parent);
    b = new MyClass("ba-a-ar", &parent);
    c = new MyClass("baz", &parent);

    qDebug() << a->text()
             << " ("
             << a->getLengthOfText()
             << " )";
    a->setText(b->text());
    qDebug() << a->text()
             << " ("
             << a->getLengthOfText()
             << " )";

    delete a;
    return a->getLengthOfText();   // <-------

}

[Disch]

The compiler doesn't complain because it's a runtime issue. a->getLengthOfText() is perfectly legal syntax, so there is no compiler error.

[CroCo]

So, is it safe to do that?

[Superdude]

Not at all.

[S6k9GNh0]

Perhaps an ideal compiler might warn you but it's not against the C++ standard to let that compile. It's your job to make sure your code doesn't do stupid things.

[JLBorges]

To help detect errors of this kind, use (ideally more than one) static analysis tools.
For instance: http://clang-analyzer.llvm.org/

To help prevent silly C-like errors of this kind, use RAII.
For instance: std::unique_ptr<MyClass> a( new MyClass("foo", &parent) ) ;