CODEWITHSUNDEEP
c++c
Brandon
Brandon

Reputation: 23515

Max amount one should allocate on the stack

I've been searching Stack Overflow for a guideline on the max amount of memory one should allocate on the stack.

I see best practices for stack vs. heap allocation but nothing has numbers on a guideline on how much should be allocated on the stack and how much should be allocated on the heap.

Any ideas/numbers I can use as a guideline? When should I allocate on the stack vs. the heap and how much is too much?

Upvotes: 4

Views: 1496

Answers (3)

Mats Petersson
Mats Petersson

Reputation: 129524

The answer here depends on the environment in which the code is running. On a small embedded system, the whole stack may be a few kilobytes. On a large system running on a desktop, the stack is typically in the megabytes.

For desktop/big embedded system, a few kilobytes is typically fine. For small embedded systems, that may not work well at all.

On the other hand, excessive use of the heap can lead to excessive overhead when calling new/delete frequently. So in a typical situation, you shouldn't use heap allocation for very small objects - unless necessary from other design criteria (e.g. you need a pointer to store permanently somewhere, and stack won't work for that as you are returning from the current function before the object has been finished with).

Of course, it's the overall design that matters. If you have a very simple application, with a few functions, none of which are recursive, it could be fine to allocate a few hundred kilobytes in main or a level above. On the other hand, if you are making a library for generic use, using more than a few kilobytes will probably not make you popular with the developers using the library. And if the library is being developed to run on low memory systems (in a washing machine, old style mobile phone, etc) then using more than a couple of hundred bytes is probably a bad idea.

Upvotes: 1

user2986109
user2986109

Reputation: 63

Allocate on the stack as small as possible. Use the heap for datasets or else the stack allocation will carry through the scope's life, possibly thrashing the cache.

Upvotes: 0

Jerry Coffin
Jerry Coffin

Reputation: 490663

In a typical case, the stack is limited to around 1-4 megabytes. To leave space for other parts of the code, you typically want to limit a single stack frame to no more than a few tens of kilobytes or so if possible. When/if recursion gets (or might get) involved, you typically want to limit it quite a bit more than that.

Upvotes: 4

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