Overloading Prefix and Postfix Operators

[geniusberry]

Hello!
I've been working through some examples on how to overload operators, and I managed to create a program with a simple class, circle, that has overloaded prefix, postfix, and addition operators. only thing is that it has an unexpected output.
Here is the class definition

class SimpleCircle {
	
	public:
	
	SimpleCircle();
	SimpleCircle(const int radius);
	~SimpleCircle();
	
	int getRadius() const {return *itsRadius;}
	void setRadius(int newRadius) {*itsRadius = newRadius;}
	
	const SimpleCircle & operator++ ();
	const SimpleCircle operator++ (int x);
	SimpleCircle operator+(const SimpleCircle & prm);
	
	private:
	
	int *itsRadius;
};

I think the problem is here:

const SimpleCircle & SimpleCircle::operator++() {
	
	cout << "Prefix!\n";
	++*itsRadius;
	return *this;
}

const SimpleCircle SimpleCircle::operator++(int x) {
	
	SimpleCircle temp(*this);
	cout << "Postfix!\n";
	++*itsRadius;
	return temp;
}

This is my main.cpp

int main() {
	
	cout << "Hello world!" << endl;
	
	SimpleCircle circle(9);
	SimpleCircle sndCircle;

	circle++;
	sndCircle++;
        ++circle;
        ++circle;
	
	cout << circle.getRadius() << "\n";
	cout << sndCircle.getRadius() << "\n";
	
	cout << "Success!" << endl;
	
	return 0;
}

I expected an output where SimpleCircle circle's radius was 11;
and sndCircle's 7 (my default constructor initializes itsRadius to 5). Instead, I got

Hello world!
0Constructor
Constructor!
Postfix!
Destructor!
Postfix!
Destructor!
Prefix!
Prefix!
1
18550785
Success!
*** Error in `./advancedclasses': double free or corruption (fasttop): 0x00000000011b1030 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x7aa16)[0x7fdc11533a16]
/lib/x86_64-linux-gnu/libc.so.6(+0x7b793)[0x7fdc11534793]
./advancedclasses[0x400b0b]
./advancedclasses[0x400d2c]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5)[0x7fdc114da995]
./advancedclasses[0x400949]
======= Memory map: ========
00400000-00402000 r-xp 00000000 08:01 4063859                            /home/ayush/Ayush/ExCodes/advancedclasses
00601000-00602000 rw-p 00001000 08:01 4063859                            /home/ayush/Ayush/ExCodes/advancedclasses
011b1000-011d2000 rw-p 00000000 00:00 0                                  [heap]
7fdc114b9000-7fdc1165c000 r-xp 00000000 08:01 4456717                    /lib/x86_64-linux-gnu/libc-2.17.so
7fdc1165c000-7fdc1185b000 ---p 001a3000 08:01 4456717                    /lib/x86_64-linux-gnu/libc-2.17.so
7fdc1185b000-7fdc1185f000 r--p 001a2000 08:01 4456717                    /lib/x86_64-linux-gnu/libc-2.17.so
7fdc1185f000-7fdc11861000 rw-p 001a6000 08:01 4456717                    /lib/x86_64-linux-gnu/libc-2.17.so
7fdc11861000-7fdc11865000 rw-p 00000000 00:00 0 
7fdc11865000-7fdc1187a000 r-xp 00000000 08:01 4456451                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fdc1187a000-7fdc11a7a000 ---p 00015000 08:01 4456451                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fdc11a7a000-7fdc11a7b000 rw-p 00015000 08:01 4456451                    /lib/x86_64-linux-gnu/libgcc_s.so.1
7fdc11a7b000-7fdc11b77000 r-xp 00000000 08:01 4456723                    /lib/x86_64-linux-gnu/libm-2.17.so
7fdc11b77000-7fdc11d77000 ---p 000fc000 08:01 4456723                    /lib/x86_64-linux-gnu/libm-2.17.so
7fdc11d77000-7fdc11d78000 r--p 000fc000 08:01 4456723                    /lib/x86_64-linux-gnu/libm-2.17.so
7fdc11d78000-7fdc11d79000 rw-p 000fd000 08:01 4456723                    /lib/x86_64-linux-gnu/libm-2.17.so
7fdc11d79000-7fdc11e5e000 r-xp 00000000 08:01 263227                     /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.19
7fdc11e5e000-7fdc1205d000 ---p 000e5000 08:01 263227                     /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.19
7fdc1205d000-7fdc12065000 r--p 000e4000 08:01 263227                     /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.19
7fdc12065000-7fdc12067000 rw-p 000ec000 08:01 263227                     /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.19
7fdc12067000-7fdc1207c000 rw-p 00000000 00:00 0 
7fdc1207c000-7fdc1209d000 r-xp 00000000 08:01 4456708                    /lib/x86_64-linux-gnu/ld-2.17.so
7fdc12271000-7fdc12276000 rw-p 00000000 00:00 0 
7fdc12299000-7fdc1229d000 rw-p 00000000 00:00 0 
7fdc1229d000-7fdc1229e000 r--p 00021000 08:01 4456708                    /lib/x86_64-linux-gnu/ld-2.17.so
7fdc1229e000-7fdc122a0000 rw-p 00022000 08:01 4456708                    /lib/x86_64-linux-gnu/ld-2.17.so
7fffaef3a000-7fffaef5b000 rw-p 00000000 00:00 0                          [stack]
7fffaeffe000-7fffaf000000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
Aborted


------------------
(program exited with code: 134)
Press return to continue

 

What did I do wrong? Any suggestions would be appreciated.

[long double main]

Why does itsRadius have to be a int*?
Why not just an int?

Your problem is most likely forgetting the "Rule of 3":
http://stackoverflow.com/questions/4172722/what-is-the-rule-of-three

In other words, when you do this:

SimpleCircle temp(*this);
cout << "Postfix!\n";
++*itsRadius;
return temp;

This copies the pointer, so this->itsRadius and temp.itsRadius are now pointing at the same thing.
Then temp gets destroyed, and along with it goes the itsRadius of the original object as well.

tl;dr: Define a copy constructor. Better yet, change itsRadius to an int and forget the pointers.

[geniusberry]

thanks for your reply! the reason I have to use int * is for a programming exercise. I would have rather used an int, but I had to use a pointer. I guess I needed to, because know I know I need the practice. Thanks for your reply!