Cutest bug you have ever seen?

[Joeman]

I was getting incorrect results although it was guaranted there should be no overflow for unsigned long long type. Still, result was incorrect. Find an error and get a rep point from me

I know!
this is pretty simple to me, but I am not a pro .

#include <iostream>
#include <string>

using namespace std;

int main()
{
	string s = "Testing";

	//iterate through string backwards
	for(size_t pos = s.length() - 1; ; --pos) {
		cout << s[pos] << endl;;
		if(pos == 0) break;

	}
}

#include <iostream>
#include <string>
#include <vector>
#include <numeric>
#include <algorithm>

using namespace std;

int main()
{
	vector<unsigned long long> vec;
	vec.push_back(123456789012LL);
	vec.push_back(987654321098LL);

	unsigned long long result = accumulate(vec.begin(), vec.end(), 0LL);
	cout << result;
}

Do you want an explanation too?

[Hobson]

Good job! And no need for explanation, I got it by myself, however, when you are learning, it may take you some time

[S_M_A]

I guess the accumulate issue was some time ago Hobson? This is captured by the compiler today.

[souldog]

well the compiler gives a warning now

[JohnW@Wessex]

I got stumped on this one for a while when I first learnt C.

// Oops, infinite loop.
unsigned char c;
for (c = 0; c < 256; c++)
{
	/// Do stuff.
}

[tossy]

I don't think its an interesting story.

[Zaccheus]

# include <iostream>
using namespace std;

int main()
{
   float f[2][2] = {1.0, 2.0, 3.0, 4.0};
   int i = (int)f[1, 1];
   cout << i << endl;
}

Oh, and as for the answer to my example: I'll leave it unsolved just to see what others think. What would the output be? Why does it compile?

Without reading other replies ...

1,1 evaluates to 1

f[1] evaluates to the address of the second row, i.e. &f[1][0]

That address is then cast to an int.

What safer coding practice would have prevented this?

Use static_cast<int> instead of (int).

[treuss]

One of the cutest bug I've seen was something like

// check if a is either 3 or 5
if (a == 3 | 5) {

And some of the cutest code (not a bug, works perfectly) I've seen was this (ok, it's JAVA, not C++):

     for(int i=2;i<8;i++){
      if(slotNumber.longValue() == i){
       slotName = "Slot "+ (i-2);
      }
     }

Both pieces were written by "IT-professionals", not students.

[S_M_A]

I must say I'm impressed guys. I've made so many bug's in my life I can't pick a favourite...

[Zachm]

For some reason, I like this one (access violation):

#include <iostream>

using namespace std;

char* numbers[10] = {
	"One",
	"Two",
	"Three",
	"Four",
	"Five"
	"Six",
	"Seven",
	"Eight",
	"Nine",
	"Ten"
};

int main()
{
	for (int i = 0; i < 10; ++i)
	{
			std::cout << numbers[i] << " ";
	}
	
	return 0;
}

[laserlight]

For some reason, I like this one (access violation):

Admittedly, I am not very familiar with the use of such global variables, but it seems to me that the problems with that example is not an access violation, but a missing semi-colon and that numbers should be an array of const char*.

EDIT:
Ah, the most obvious mistake is now corrected.

[Zachm]

Edited my last post.
Didn't try to compile it, but the semi-colon is not the problem I intended to demonstrate.
Disregard the fact that the array is global as well - this was just for demonstration purposes,
and look closer !

[laserlight]

hmm... after seeing your correction, I thought that perhaps I miscounted, but you have ten string literals in the array, and the array is of 10 char*, so where's the out of bounds access?

[Hobson]

Zachm, your code snippet just killed me. Awesome. I was staring at it trying to find a bug for like 15 minutes, until decided to run it and see. Great example

[laserlight]

Zachm, your code snippet just killed me. Awesome. I was staring at it trying to find a bug for like 15 minutes, until decided to run it and see.

I ran it and did not get a seg fault... but I guess I was unlucky.

Yeah, I see the error now, but frankly, it was obscured by other mistakes