C/ObjC - parameter size. Using a pointer vs value

at what point should I be passing a pointer to data in my functions/methods, rather than just passing the value?

Obviously there's the cases where I want the function to operate on the given data, but what if I'm just passing the value for info/copying purposes?

For example, foo as a basic type:

void setFoo(int foo);
...
int foo = 1;
setFoo(foo);开发者_如何学JAVA

Now foo as a simple structure:

typedef struct {
    int x;
    int y;
} Foo;

void setFoo(Foo foo);
...
Foo foo = {1, 2};
setFoo(foo);   // Apple code does this kind of thing with CGSize, CGPoint...

But what if foo is a bigger struct...

typedef struct {
    int x;
    int y;
    int z;
    char str[256];
} Foo;

void setFoo(Foo *foo);  // Now taking a pointer instead.
...
Foo foo = {1, 2, 3, etc ... };
setFoo(&foo);

Q. At what point here should I start using a pointer when providing data to a function?

Thanks

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When on embedded systems, I think it's good practice to pass pointers (or references) for anything that's not a primitive type. This way your struct can grow and add members as needed without affecting the amount of data that is copied. Needless copying is a good way to slow down your system, so avoid it when you can. Getting into that habit will help in the long run I think.

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If you use references and/or pointers to [const] objects as appropriate, "when" becomes "all the time"