What are reentrant functions and why are they important?

What are reentrant functions and why are they important?

Reentrant functions are functions that can be interrupted in the middle of execution and safely called again ('re-entered') before the previous executions are complete. They are important in concurrent programming because they allow multiple threads to execute the same function without causing data corruption.

Can you give me an example of a reentrant function?

Sure! A classic example of a reentrant function is one that uses local variables only. For instance, a function that calculates the factorial of a number using a local variable to store the result is reentrant, as each call to the function will have its own instance of that variable.

What about non-reentrant functions? What makes them different?

Non-reentrant functions typically use shared resources or static/global variables, which can lead to issues if the function is interrupted and called again. This can result in data corruption or unexpected behavior.

How can I make a function reentrant?

To make a function reentrant, ensure it only uses local variables, avoid static/global variables, and manage shared resources carefully, often using synchronization mechanisms.