[daengh]

He also said his statement "This is never about what runs fastest...". Kernel code needs to run fast and take advantage of shortcuts.

IME, the jobs most programmers are doing don't need to try to accomplish maximum speed or need to wring a few bytes out of RAM. Certainly we don't want to be wasteful, but long-term maintainability is more important, again IME, than absolute speed or minimising memory footprint by a few (k) bytes.

Back in the bad old days when I was writing programs to run on mainframes, yeah, we did need to fight for every byte. A $5 million machine back then had less RAM and less raw CPU power than a tablet does today. We don't live in that world now.

[masklinn]

> He also said his statement "This is never about what runs fastest...".

This style has nothing to do with running fast, it has to do with lowering the cognitive load of the rest of the function. A branch means you have two states to keep in mind (the state where the branch is taken, and the state where the branch is not taken). Without early exit, you have to keep both states in mind until the end of the function just in case.

With guard clauses, you can discard on of the states (the one which matched the clause) entirely.

[daengh]

Computers can do that repeatedly and reliably with even (hundreds of) thousands of discarded states. People reading code and trying to understand what's actually in play at line umptyfratz of function iGottaGetThisFixedNow(), not so much.

In the end, I'm not disagreeing with early exits per se, just that over time they can make it more difficult to understand function because assumptions about state have to adjust as a maintainer goes through the code. Those assumptions may have been crystal-clear to the writer originally but how many times is the original writer the only maintainer?