When does the stack really overflow?

Question

Aryan Kumar · Answer

The stack overflow can happen when a program uses more stack than the stack has. This can generally happen in the following cases:

When a recursive function calls itself too many times. For example, the following code will cause a stack overflow:

public void RecursiveFunction(int n) {
  if (n > 0) {
    RecursiveFunction(n - 1);
  }
}

When a program allocates large amounts of memory on the stack. For example, the following code will cause a stack overflow:

public void LargeAllocation() {
  var array = new byte[1024 * 1024];
}

When a program has a bug that causes it to allocate too much memory on the stack. For example, the following code has a bug that causes it to allocate too much memory on the stack:

public void BugFunction() {
  var array = new byte[int.MaxValue];
}

The stack overflow can cause the program to crash or to behave in an unexpected way.

There are a few things that can be done to prevent stack overflows:

Avoid using recursive functions. If you do need to use recursive functions, try to use them sparingly and make sure that they do not call themselves too many times.
Avoid allocating large amounts of memory on the stack. If you need to allocate large amounts of memory, try to allocate it on the heap instead.
Have your code reviewed by a qualified engineer. If you are not sure whether your code is prone to stack overflows, have it reviewed by a qualified engineer.

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