CODEWITHSUNDEEP
objective-cc
egghese
egghese

Reputation: 2223

How does static keyword work internally?

How does the static keyword works internally? Considering the base definition static variable is initialized only once, how does the run-time or compile time interprets it in terms of execution flow? Consider code snippet:

void function()
   {
      static int count=0;
      count++;
   }
main()
    {
       for(int i=0;i<=10;i++)
          function();
    }

The line static int count=0; is executed only once and that to in iteration i=0 is the best explanation I can come up with. Is it correct or does it work some other way?

And where in memory is a static variable stored stack or heap?

Also is there something called static object in Objective-C? If there is how is it different from normal object?

Upvotes: 0

Views: 540

Answers (2)

newts
newts

Reputation: 85

It means something to the compiler and to the way memory is allocated depending on where it is. Inside a function variables are allocated on the stack and persist for the life of the function and the value is not retained between calls. With a static declaration the variable is allocated where globals are allocated (usually .bss) and the value persists between function calls but the scope of the variable is only to that function.

When static is used for global declarations outside of a function then the variable only has scope in that module. That is if you declare a static variable in module1.cpp then module2.cpp cannot access it with extern.

Upvotes: 2

Luchian Grigore
Luchian Grigore

Reputation: 258618

Your last question suggests you're asking about the case where static is used in a local variable declaration.

How does the static keyword work internally?

That's implementation-specific.

Does this have anything to do with the memory being allocated?

Yes, locals declared with static reside in static storage.

does the compiler/runtime just skip it after the first encounter?

It's the runtime that executes the initialization only once. static locals are value-initialized, unless otherwise noted.

Upvotes: 5

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