Conditionals and Loops

Detecting Infinite Loops

How can I detect and prevent infinite loops in my C++ code?

Abstract art representing computer programming

Detecting and preventing infinite loops is an important aspect of writing robust and reliable C++ code. Here are a few techniques you can use to identify and avoid infinite loops:

Analyze loop conditions

  • Ensure that the loop condition eventually becomes false. If the condition always remains true, the loop will continue indefinitely.
  • Check for proper initialization and updating of loop variables.

Use a counter or a flag

  • Introduce a counter variable that increments with each iteration and set a maximum limit. If the counter exceeds the limit, break the loop and log an error.
  • Use a flag variable to indicate a specific condition that should terminate the loop.
#include <iostream>

int main() {
  int count{0};
  while (true) {
    if (count > 1000) {  
      std::cout << "Potential infinite loop"
        " detected. Breaking...\n";
Potential infinite loop detected. Breaking...

Utilize debugging tools

  • Use a debugger to step through the code and observe the loop's behavior.
  • Set breakpoints and inspect variable values to identify why the loop continues indefinitely.

Test with different inputs

  • Provide various inputs to your program, including edge cases, to ensure the loop behaves as expected.
  • Consider writing unit tests that cover different scenarios and verify the loop's termination.

Review and reason about the code

  • Carefully read and understand the purpose and logic of the loop.
  • Identify any missing or incorrect loop control statements.
  • Verify that the loop progresses towards its intended termination condition.

In this example, the loop variable i is not incremented, causing an infinite loop:

#include <iostream>

int main() {
  int i{0};
  while (i < 10) {
    std::cout << i << "\n";
    // Missing increment statement 

Set a timeout or a maximum execution time

  • In some cases, you can set a timeout or a maximum execution time for your program.
  • If the loop exceeds the specified time limit, terminate the program and log an error.

Example using std::chrono:

#include <chrono>
#include <iostream>

int main() {
  using namespace std::chrono;
  auto start = steady_clock::now();
  while (true) {
    auto current = steady_clock::now();
    auto duration = duration_cast<seconds>(
      current - start);
    if (duration.count() > 5) {  
        << "Timeout exceeded. Terminating...\n";
Timeout exceeded. Terminating...

By applying these techniques and being cautious when writing loop conditions, you can detect and prevent infinite loops in your C++ code, ensuring more stable and predictable program behavior.

Answers to questions are automatically generated and may not have been reviewed.

A computer programmer
Part of the course:

Professional C++

Comprehensive course covering advanced concepts, and how to use them on large-scale projects.

Free, unlimited access

This course includes:

  • 124 Lessons
  • 550+ Code Samples
  • 96% Positive Reviews
  • Regularly Updated
  • Help and FAQ
Free, Unlimited Access

Professional C++

Comprehensive course covering advanced concepts, and how to use them on large-scale projects.

Screenshot from Warhammer: Total War
Screenshot from Tomb Raider
Screenshot from Jedi: Fallen Order
Contact|Privacy Policy|Terms of Use
Copyright © 2024 - All Rights Reserved