When should we use asserts in C?

Question

I am writing a function in C. As a matter of style, when is it good to use assert compared to returning an error code. Lets say the function is dividing two numbers. Should

Answer 1

This is really a matter of taste. Here is my opinion.

The main rule of thumb: an assertion failure is always a bug in the program.

Use an assert to check function parameters if you expect the caller to ensure that the argument is correct and you want to indicate that any other behavior is a bug in the caller. Dividing by zero is, IMO, a very good example.

Use an error code if you expect the caller not to be able to ensure that the argument is correct before calling. For example, it could be very computationally expensive to check the arguments beforehand.

Never use an assert to check user input.