How do I implement reentrant functions?

What are reentrant functions and why are they important?

Reentrant functions are functions that can be interrupted and safely called again ('re-entered') before the previous executions are complete. They are crucial in multi-threaded environments to avoid data corruption.

Can you give me an example of a reentrant function?

Sure! A simple example is a function that uses local variables only, like this:

int add(int a, int b) {
    return a + b;
}

This function is reentrant because it doesn't rely on shared state.

What about functions that use global variables?

Functions that use global variables are generally not reentrant unless they manage access to those variables carefully, often using locks or other synchronization mechanisms.

How can I make a non-reentrant function reentrant?

You can make a non-reentrant function reentrant by eliminating shared state, using local variables, or implementing proper synchronization techniques to manage access to shared resources.