Stack Overflow

Stack overflow is an error in programming that a user-mode thread encounters when attempting to write more data but the memory block is running out of space to hold it.

There are two types of overflow errors: the first one can immediately cause the program to crash. The second remains undetected allowing the program to run after the error, which is harder to trace and more challenging to debug.

What are the symptoms of a stack overflow? 

A stack overflow might appear as a segmentation fault, leaving without a clue where it occurs and how it happened. This is often the case in C++. The signs of an overflow usually depend on the language or the mechanism for error reporting. In Java, however, the virtual machine could crash, as it handles memory inside it, leaving an error file that might further baffle users. The root cause of the overflow is harder to find.  

Once an overflow is detected, you can correct it right away by identifying the source and by debugging the error. Programming languages that allow explicit memory management can prevent these overflows by adjusting the program’s memory allocation to keep the usage to a minimum. Computer languages with implicit memory management encounter difficulty in safeguarding against stack overflow, causing the machine to crash, potentially halting the entire program.

What causes overflow errors in a program?

There are three possible causes of a stack overflow: 

1. Infinite recursion that causes the thread to use the entire reserved memory stack.
2. A maxed-out page file is unable to add more pages, which results in the thread failing to extend the stack.
3. The system is within the time or in the process of extending the page file when the thread attempts to extend the stack.

There should be ample stack space allocated to local variables when a function runs on a thread. Reduced space risks the stack overflowing.

How is stack overflow different from heap overflow?

There’s an area of the memory where local variables used in the function are stored. It is called a stack, which has a Last In-First Out data structure. New local variables are pushed to the stack, and the variables associated with the function get deleted after running to free up memory space. When the stack runs out of space due to a program using more memory space than the stack size, an error or an overflow occurs.

Heap overflow happens when a leak occurs with the memory that stores dynamic variables. Memory on heap is manually allocated and resized using malloc(), calloc(), and realloc() functions. A failure to free up memory space after use results in a memory error.

How to fix a stack overflow?

Microsoft documentation identifies the steps to take in correcting a stack overflow:

1. Establish the event that causes the error by investigating the target process’ stack usage.
2. Identify the thread in the stack that causes the overflow.
3. Calculate the stack size and start debugging.