Code Craft

Detecting Errors

How you detect an error obviously depends on the mechanism reporting it. In practical terms, this means:

Return values

You determine whether a function failed by looking at its return code. This failure test is bound tightly to the act of calling the function; by making the call, you are implicitly checking its success. Whether or not you do anything with that information is up to you.

Error status variables

After calling a function, you must inspect the error status variable. If it follows C’s errno model of operation, you don’t actually need to test for errors after every single function call. First reset errno, and then call any number of standard library functions back-to-back. Afterward, inspect errno. If it contains an error ...