Static function vs Static member functions C++ [duplicate]

Question

I've been reading a bit about static functions and static member functions. From my understanding if a function is declared static then this function is only visible to it's translation unit and nowhere else. A static member function instead is a function that can be called without instantiating any object of its class (so you can use it like it was in a name space).

To clarify with static function I mean something like

static int foo(int a, int b)
{
   return a + b;
}

And with static member function I mean

struct MyClass
{
   static int foo(int a, int b)
   {
      return a + b;
   } 
}

Is this the only difference? or is the visibility within the same translation unit still a common feature for the two of them?

Are you only asking about internal/externable linkage or are you looking for all differences? E.g., a static member function can be called using the dot operator on an instance of the class, while a static nonmember function cannot. — AndyG
– AndyG, Commented Apr 20, 2020 at 12:01
A static member function is still a member function, it just doesn't need an object to be called on (which means it has no this pointer). It can be seen as a class-function instead of an object-function, and is available for all translation units which have the declaration of it. A static non-member (also called namespace-scope) function have static storage duration and internal linkage. — Some programmer dude
– Some programmer dude, Commented Apr 20, 2020 at 12:02
static is one of the keywords with different meanings depending on context. Don't get confused by the same keyword being used for different things (en.cppreference.com/w/cpp/keyword/static) — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Apr 20, 2020 at 12:02
@user8469759: Then it seems you understand it well enough already. Just bear in mind that in gcc symbols are exported by default but in MSVC we need to explicitly export/import them with the __declspec directive. So even for a static member function, it may not be visible outside its translation unit in Windows unless you make it so. — AndyG
– AndyG, Commented Apr 20, 2020 at 12:06

smailzhu · Accepted Answer · 2022-11-15 12:46:38Z

12

As you can see on this page, static actually has 3 different meanings depending on where it's used.

If it's used inside a block scope, like inside a function, then it'll make a variable persist across function calls.
If a class method is declared as static, then it's not bound to a specific instance of the class.
If a namespace member is declared as static, then it has internal linkage only.

edited Nov 15, 2022 at 12:46

smailzhu

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answered Apr 20, 2020 at 12:04

Aplet123

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1 Comment

user8469759 Over a year ago

Ok, so the differences I spot where the right ones then.

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