CODEWITHSUNDEEP
c++arduino
Cerin
Cerin

Reputation: 64739

How to minimize memory allocation on embedded platforms?

How do you minimize dynamic memory allocation in C++?

I'm writing some sketches for an Arduino Mega, and on occasion it's hanging, and I suspect it's suffering from memory fragmentation. However, I'm a little unclear as to when variables are allocated.

If I have a class with a method do_stuff like:

class MyController{

public:
    MyController(){
        ...init...
    }

    void do_stuff(){
        int value = 123;
    }
};

I instantiate MyController once but then execute do_stuff() multiple times. Does the program dynamically allocate value each time I call the method or just once when I instantiate the class?

If the former, would it be better to change the method variable to a class variable, so it's only allocated once, and doesn't risk fragmenting the heap?

Upvotes: 1

Views: 127

Answers (2)

MSalters
MSalters

Reputation: 179907

On typical platforms, and I don't believe an Arduino is different in this respect, int value probably won't take memory. It will be in a register. (Small variable, local). If not, it will be on the CPU stack, which doesn't fragment, and it recycled whenever the function returns.

Upvotes: 2

Jerome Reinländer
Jerome Reinländer

Reputation: 1257

I can't say where MyController will be instantiated, but each call of do_stuff instantiates value on the stack once. This memory will be freed as soon as do_stuff is left and since there is no recursion, there will not be several instances of value at once.

Upvotes: 0

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