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Static storage duration

From cppreference.com
< c‎ | language

An object whose identifier is declared without the storage-class specifier _Thread_local, and either with external or internal linkage or with the storage-class specifier static, has static storage duration. Its lifetime is the entire execution of the program and its stored value is initialized only once, prior to program startup.

[edit] Notes

Since its stored value is initialized only once, an object with static storage duration can profile the invocations of a function.

The other use of the keyword static is file scope.

[edit] Example

Profiling the invocations of function f().

#include <stdio.h>
 
void f (void)
{
    static int count = 0;   /* static variable    */
    int i = 0;              /* automatic variable */
    printf("%d %d\n", i++,count++);
    return;
}
 
int main(void)
{
    for (int ndx=0; ndx<10; ++ndx)
        f();
 
    return 0;
}

Possible output:

0 0
0 1
0 2
0 3
0 4
0 5
0 6
0 7
0 8
0 9