This content originally appeared on DEV Community and was authored by Shaw
static can be confusing with the wrong definition. Here's a simplified example:
The task is to write a counter function that takes no arguments and returns a different number each time, starting at 0 and adding 1 each time.
int current_counter = 0;
int counter(void) {
return current_counter++;
}
Now imagine someone is using this library. They write a function called counter just for testing. But when they try to link their code, it fails, telling them that counter is being redefined. But no worry, We are C programmers and we have static at our disposal!
Many believe static to have multiple meanings in C.
- static functions are not exported globally
- static local variables are hidden globals
- static global variables are not exported globally What could have caused this mess of keyword overloading?
The answer lies in a shift of perspective. static means compilation unit local. A compilation unit in C is just the files given to the c compiler (gcc, clang, msvc, etc) and what they #include.
Using this definition we can say the following.
- static functions are owned by the compilation unit
- static global variables are owned by the compilation unit
- static local variables are owned by the compilation unit
Using this knowledge, we can rewrite the counter function to not leak counter into the API.
First, move current_counter into a static in counter
int counter(void) {
static int current_counter = 0;
return current_counter++;
}
This will make current_counter not collide with anything else named current.
Next is to make counter a static function
static int counter(void) {
static int current_counter = 0;
return current_counter++;
}
This will make counter not visible to files not in the same compilation unit.
Now things are fixed! The counter function and current_counter variable cannot be used in files not in the same compilation unit.
I hope this helped someone.
This content originally appeared on DEV Community and was authored by Shaw
Shaw | Sciencx (2021-12-09T18:17:54+00:00) static has only one meaning. Retrieved from https://www.scien.cx/2021/12/09/static-has-only-one-meaning/
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