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With static in C one can keep a stack variable around, even after the creating function exists.

In this case however, 

void static_func() {
    static int var = 1;
    var += 1;
}

I can access var outside of the static_func() and return its value. Let's assume static_func() is called three times in the main(), then the value of var is 3.

However, it is set to 1 every time the function is executed. Why do I still get the value 3?!

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12
  • static and static variables mean something different. Commented Jun 2, 2016 at 14:38
  • 3
    "However, it is set to 1 every time the function is executed." Why? Because your compiler contains a bug? Commented Jun 2, 2016 at 14:38
  • 2
    And where is your stack? This is no keyword in C, nor does C require a stack. And typical implementations which use a stack don't store static variables (which are a subset of static variables) on the stack. Commented Jun 2, 2016 at 14:39
  • @MikeCAT I do not hope so! ;) Commented Jun 2, 2016 at 14:43
  • 1
    "I can access var outside of the static_func()" - If that is true, instantly rm -f $YOUR_COMPILER_BINARY_WITH_PATH. And (1 + 3 * 1) == 4, not 3. Commented Jun 2, 2016 at 14:45

2 Answers 2

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6

Once you say static int var = 1;, this variable is created and initialized. This can happen only once, otherwise you're gonna flood your memory with useless duplicates since this variable will stay alive during whole program runtime.

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4

The initial value of a static variable is only applied once at program startup. It doesn't happen each time the function is entered.

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