Dynamic Memory and the Free Store

Identifying Memory Leaks

How can I tell if my C++ program has a memory leak?

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Memory leaks can be tricky to identify because they don't typically cause your program to immediately malfunction. Instead, they gradually consume more and more memory over time.

Here are a few strategies for identifying memory leaks:

  1. Use a memory profiler. Many IDEs have built-in memory profilers, or you can use standalone tools. These tools can track memory allocations and deallocations and highlight leaks.
  2. Manually track allocations and deallocations. In a complex program, this can be tedious, but in simpler programs, you can simply make sure that every new has a corresponding delete.
  3. Pay attention to performance over time. If your program's memory usage keeps growing the longer it runs, even for the same workload, that's a strong indication of a memory leak.
  4. Use smart pointers and standard containers. While not foolproof, using std::unique_ptr, std::shared_ptr, std::vector, etc., can dramatically reduce the likelihood of memory leaks, as they handle deallocation for you.

Here's an example of a memory leak:

void func() {
  int* ptr = new int(10);

  return; // Leak: ptr is never deleted 

And here's how you might fix it:

void func() {
  int* ptr = new int(10);
  // ...
  delete ptr;

Or, even better, with a smart pointer:

#include <memory>

void func() {
  std::unique_ptr<int> ptr{

  // ...
  // ptr will be automatically deleted

Remember, every new should have a corresponding delete, and if you find manual memory management cumbersome, use smart pointers and containers instead.

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

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