Where do function variables go to?

Question

When I'm declaring a variable in a function, I'm using some memory. When the function is done doing it's job, is the memory getting freed?

have you ever heard about "stack"? - I guess you are talking about basic type, otherwise there could be also used the heap, and it's memory get freed when the var goes out of scope (or alike), if the class provides a correct destructor... (Not if you created the instance with new, of course: in this case it's your duty) — ShinTakezou, Jan 08 '14 at 15:21

score 6 · Answer 1 · answered Jan 08 '14 at 15:22

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All automatic storage variables will be freed when they go out of scope, and you have to be explicit about dynamically allocated ones:

void foo()
{
    int x;
    int* y = new int;
    //You get a memory leak with each call to foo without the following line
    delete y;
} //x is freed here

answered Jan 08 '14 at 15:22

Luchian Grigore

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There is no such thing as dynamic variables. There are only dynamic *objects*. All variables are scoped; the have the same scope as their name. (So `y` just goes out of scope as it should and all is well.) – Kerrek SB Jan 08 '14 at 15:27
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@KerrekSB Is this some kind of a joke? – Sceptical Jule Jan 08 '14 at 15:31
@ScepticalJule: Nope, it's trying to fix an erroneous answer :-) – Kerrek SB Jan 08 '14 at 15:31
@KerrekSB He said 'dynamically allocated' variables, not 'dynamic variables'. This is a pretty relevant difference. – Kevin Jan 08 '14 at 15:33
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@Kevin: You cannot allocate variables. You can only allocate objects. – Kerrek SB Jan 08 '14 at 15:35

score 1 · Answer 2 · edited May 23 '17 at 10:33

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Perhaps most importantly is you understand the concepts of a stack and a heap and this post as very good explanations on the subject:

What and where are the stack and heap?

Cleverness aside (auto_ptrs and the like), the gist of it is that if they are allocated in the stack then they are freed when they leave the scope, otherwise you need to take care to free them yourself. If you understand the above you'll get a better understanding of what to look for.

edited May 23 '17 at 10:33

Community

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answered Jan 08 '14 at 15:38

RMo

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You should read about automatic and dynamic storage duration, because you have misunderstood "stack and heap". – Lightness Races in Orbit Jan 09 '14 at 18:51
@Lightness Races in Orbit - It's not that I have misunderstood stack and heap IMO, but you're correct that in C++ terms I should have described it in those terms. In the end your variables can only be in a stack or heap, and you only free those when the stack unwinds or you call deallocation functions, respectively. I do take your point, though! – RMo Jan 10 '14 at 08:37
You mean "objects" not "variables" and they can absolutely be in something other than a stack or a heap. _That_'s the point! :) – Lightness Races in Orbit Jan 10 '14 at 16:20

Where do function variables go to?

2 Answers2