Can you give an example of stack overflow in C++?

Question

You want me to implement the whole stackoverflow website in C++ in my answer? Wow... :) — dicroce, Nov 01 '09 at 15:57
The above won’t overflow on a decent compiler. No stack, no operation, no nothing. — Konrad Rudolph, Nov 01 '09 at 18:42

score 23 · Accepted Answer · answered Nov 01 '09 at 16:04

23

The typical case that does not involve infinite recursion is declaring an automatic variable on the stack that is too large. For example:

int foo()
{
    int array[1000000];

}

answered Nov 01 '09 at 16:04

Tall Jeff

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score 11 · Answer 2 · answered Nov 01 '09 at 15:54

11

Please see Stack overflow - Wikipedia. I have linked directly to the examples section.

answered Nov 01 '09 at 15:54

Andrew Hare

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score 8 · Answer 3 · edited Feb 08 '23 at 06:33

8

void function() 
{
    function();
}

edited Feb 08 '23 at 06:33

AustinWBryan

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answered Nov 01 '09 at 15:54

John Boker

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1

+1 clean and straightforward. This is ALL you need to blow the stack. – Paul Sasik Nov 01 '09 at 16:01
1

Can we make it shorter? Yes, we can! `void _(){_();}` ... it's almost like Perl ;) – Thomas Nov 01 '09 at 16:08
1

The difference is, in Perl land, it's more likely that you'll blow *your* stack before Perl does. – Rob Nov 01 '09 at 16:09
2

Since this function takes no arguments, declares nothing, and returns nothing, I wonder if a smart optimizer might simple turn this into an infinite loop, in which case, it would not blow the stack... – dicroce Nov 01 '09 at 17:33

score 6 · Answer 4 · edited May 23 '17 at 12:24

6

Here's one that might happen in practice:

int factorial(int x) {
  return x == 0 ? 1 : x * factorial(x-1);
}

This overflows the stack for negative x. And, as Frank Krueger mentioned, also for too large x (but then int would overflow first).

edited May 23 '17 at 12:24

Community

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answered Nov 01 '09 at 15:58

Thomas

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score 3 · Answer 5 · answered Nov 01 '09 at 15:55

3

Keep trying to return main until the stack runs out?

int main(int argc, char **argv)
{
    return main(argc, argv);
}

answered Nov 01 '09 at 15:55

Mark Rushakoff

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3

It's not legal to call main() in C++. – Tmdean Nov 01 '09 at 16:46
I know it won't format correctly, but there's no warnings with `-Wall` even for this more proper program: int main(int argc, char **argv) { if (argc == 0){return 0;} else {std::cout << argc << std::endl; return main(0, argv);} } – Mark Rushakoff Nov 01 '09 at 17:41
I mean it's odd that `g++` doesn't give any warnings when you call main; you are indeed correct (from what I've seen) that the standard disallows calling `main`. – Mark Rushakoff Nov 01 '09 at 17:45
@Mark Rushakoff: g++ does give an error if you compile with the `-pedantic` flag, although in my case it gives the somewhat incorrect error of `ISO C++ forbids taking address of function '::main'` – Adam Rosenfield Nov 01 '09 at 18:45

score 3 · Answer 6 · edited Feb 08 '23 at 06:33

3

As per edit :-)

void ping()
{
    pong();
}

void pong()
{
    ping();
}

Also, I believe you can get stack overflow if you try to allocate more space than maximum thread stack size ( 1MB by default in VS), so something like int a[100000]; should provide the exception.

edited Feb 08 '23 at 06:33

AustinWBryan

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answered Nov 01 '09 at 15:59

Naveen

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score 3 · Answer 7 · answered Nov 01 '09 at 18:19

3

Compile-time example:

template <int N>
struct Factorial {
    enum { value = N * Factorial<N - 1>::value };
};

// ...
{
    int overflow = Factorial<10>::value;
}

answered Nov 01 '09 at 18:19

wilhelmtell

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score 2 · Answer 8 · answered Nov 01 '09 at 16:04

I can't believe we left off the greatest recursion example of all time, factorial!

#include <stdio.h>

double fact(double n) {
    if (n <= 0) return 1;
    else return n * fact(n - 1);
}

int main() {
    printf("fact(5) = %g\n", fact(5));
    printf("fact(10) = %g\n", fact(10));
    printf("fact(100) = %g\n", fact(100));
    printf("fact(1000) = %g\n", fact(1000));
    printf("fact(1000000) = %g\n", fact(1000000));
}

On OS X 10.5.8 with GCC 4.0.1:

$ gcc f.c -o f && ./f
fact(5) = 120
fact(10) = 3.6288e+06
fact(100) = 9.33262e+157
fact(1000) = inf
Segmentation fault

Unfortunately, OS X reports a "Segmentation fault" instead of a "Stack overflow". Too bad.

score 1 · Answer 9 · answered Nov 01 '09 at 15:55

1

This example shows uncontrolled recursion. Eventually, the stack spaced allocated to this process will be completely overwritten by instances of bar and ret...

int foo( int bar )
{
    int ret = foo( 42 );
    return ret;
}

answered Nov 01 '09 at 15:55

dicroce

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score 1 · Answer 10 · answered Nov 01 '09 at 16:34

If you want to generate an explicitly non-recursive program to result in a stack overflow by function calls:

#!/usr/bin/env python
import sys

print "void func" + sys.argv[1] + "() { }"
for i in xrange(int(sys.argv[1])-1, -1, -1):
    print "void func" + str(i) + "() { func" + str(i+1) + "(); }"
print "int main() { func0(); return 0; }"

Sample output:

$ python recursion.py 5
void func5() { }
void func4() { func5(); }
void func3() { func4(); }
void func2() { func3(); }
void func1() { func2(); }
void func0() { func1(); }
int main() { func0(); return 0; }

Sample usage:

$ python recursion.py 250000 | g++ -x c++ - && ./a.out

At least on my system, the call stack seems to be 174602, so you'll need to set the argument to recursion.py to be larger than that; and it takes a few minutes to compile and link the program.

score 0 · Answer 11 · answered Nov 01 '09 at 15:56

0

Infinite recursion:

void infiniteFunction()
{
    infiniteFunction();
}

int main()
{
    infiniteFunction();
    return 0;
}

answered Nov 01 '09 at 15:56

Krzysztof Bujniewicz

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score 0 · Answer 12 · answered Nov 01 '09 at 16:06

0

You could also get a stack overflow if you try to put large objects on the stack (by-value).

answered Nov 01 '09 at 16:06

EricSchaefer

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Can you give an example of stack overflow in C++?

12 Answers12

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