Identifying Memory Leaks
How can I tell if my C++ program has a memory leak?
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:
- 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.
- 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 correspondingdelete
. - 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.
- 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{
std::make_unique<int>(10)};
// ...
// 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.
Dynamic Memory and the Free Store
Learn about dynamic memory in C++, and how to allocate objects to it using new
and delete