Memory leaks - the horror of every programmer?

Question

I'm programming a game engine in C++, which also has Lua support.

My biggest horror: Memory leaks.

It's not like my game is already infested with them, I'm rather afraid of them popping out of the ground like mushrooms, when the development is in a late phase and the project huge and complex.

I'm afraid of them because they seem extremely hard to spot for me. Especially in sophisticated systems. If my engine is almost finished, the game runs and the memory gets eaten away, what will I do? Where will I start searching?

• Is my fear of memory leaks justified?
• How can one find out where a memory leak lies?
• Aren't there good tools which help in finding the source of memory leaks today?

Answer 1

How can one find out where a memory leak lies?

Valgrind

Answer 2

Raw pointers are only one potential cause of memory leaks.

Even if you use smart pointers, like shared_ptr, you can get a leak if you have a cycle - the cure for this is to use a weak_ptr somewhere to break the cycle. Using smart pointers is not a cure-all for memory leaks.

You can also forget a virtual destructor in a base class, and get leaks that way.

Even if there are no problems with new-ed objects not being deleted, a long-running process can grow (and appear to leak) because of address space fragmentation.

Tools like valgrind are very, very useful for finding leaks, but they won't always tell you where the fix should be (e.g. in the case of cycles or objects holding onto smart pointers)