When might you not want to use garbage collection? [closed]

Question

Garbage collection has been around since the early days of LISP, and now - several decades on - most modern programming languages utilize it.

Assuming that you're using one of these languages, what reasons would you have to not use garbage collection, and instead manually manage the memory allocations in some way?

Have you ever had to do this?

Please give solid examples if possible.

Answer 1

I can think of a few:

Deterministic deallocation/cleanup

Real time systems

Not giving up half the memory or processor time - depending on the algorithm

Faster memory alloc/dealloc and application-specific allocation, deallocation and management of memory. Basically writing your own memory stuff - typically for performance sensitive apps. This can be done where the behavior of the application is fairly well understood. For general purpose GC (like for Java and C#) this is not possible.

EDIT

That said, GC has certainly been good for much of the community. It allows us to focus more on the problem domain rather than nifty programming tricks or patterns. I'm still an "unmanaged" C++ developer though. Good practices and tools help in that case.

Answer 2

Memory allocations? No, I think the GC is better at it than I am.

But scarce resource allocations, like file handles, database connections, etc.? I write the code to close those when I'm done. GC won't do that for you.